Military Architecture of the 100-ton Gun Batteries

Of Gibraltar and Malta Part I.

The 100-ton Armstrong coastal guns of Gibraltar and Malta have always generated considerable interest among students of fortification and coastal artillery.  What has been less forthcoming, perhaps, is a study of the architectural features and the issues involved in the design, layout, and construction of the fortified works which were built to house and protect these singular leviathans. What were, for example, the design criteria that influenced the planimetric layout of the batteries and their component parts, and how did the use of concrete and other materials influence  overall design and construction ? How did these and other architectural issues affect the batteries’ performance as defensive works?  What were the batteries’ true ‘powers of resistance’ when faced with direct bombardment or landward assault? This article (spread over two parts) sets out to examine and draw attention to such issues generally ignored elsewhere. It does not, however, pretend to answer all the questions raised at this stage, since many of concepts and matters discussed here need to be studied further. It is the present author’s intention to publish the product of such research on the subject in a forthcoming publication on British military architecture in the Mediterranean, a new work that seeks to follow in the footsteps of Prof. Quentin Hughes’ seminal study entitled Britain in the Mediterranean and the Defence of her Naval Stations, published in Liverpool in 1981. Detailed sectional elevations and plans, together with brief historical descriptions of the Cambridge and Rinella batteries, reproduced from their respective record plans, were published by the present author in his British Military Architecture in Malta, printed in 1996, and can be consulted in that publication.  The scope of the present contribution is to provide additional new material together with 3D computer models that allow readers to better appreciate the shape, form, and structure of the 100-ton gun batteries.


Contextual significance

Although the 100-ton guns were the central feature of these singular batteries ‒ and indeed, these structures were designed and built around the very guns themselves ‒ their protective perimeters (found only in the two works erected at Malta) did not  depend on the central gun for their defence.  As rightly remarked by Maj. O’Callaghan and Capt. Clarke in 1886, the 100-ton gun was hardly the weapon to be ‘called upon to defend its own glacis.’  In defensive terms, therefore, the elements of the batteries’ fortified enclosures – i.e., the revetments, the parapets, the ditches, the caponiers and the musketry galleries  –  functioned independently of the main weapon which they were built to house.  Consequently, it was the scope and scale of these various structural elements (or lack thereof) and, ultimately, of their manner of construction, that defined the capabilities and limitations of the 100-ton gun batteries’ defensive qualities as works of fortification.

At the 100-ton gun batteries erected at Gibraltar and Malta it became more than obvious, perhaps for the first time in the history of fortification,  that it was the gun and not the stone and mortar of the structures which housed it, that had become the most important element in defence. These batteries and their guns show how technology had irrevocably changed the nature and role of permanent fortifications once close-in defence had all but given way to a wider, long-range strategic territorial defence – made possible by the longer ranges which guns were then becoming increasingly capable of.

The modern ‘automated’ fort had evolved into a dedicated artillery battery, a container for cannon so to speak, its one primary function to service and protect the massive and expensive guns that were now necessary to provide the real barrier against attack and invasion. The architecture of these works of fortification reveals in no unclear terms how ‘modern’ fortifications had evolved into structures that were little more than over-sized gun emplacements. At Gibraltar, the 100-ton gun batteries even dispensed altogether with any sense of formal enclosure or the notion of a protective perimeter, losing the barrack accommodation, ditch, flanking devices (the caponiers and counterscarp gallery) and other components in the process.

Above, one of the many British barbette gun emplacements arming the coastal defences around the heavily protected entrance to the Grand Harbour of Malta during the 1860s. (Image source – Author’s private collection).



Historical Background

The events that led to the British investment in its 100-ton gun batteries have been discussed elsewhere in various books and do not need to be repeated here.  Readers interested in the history of the gun, its technicalities, and other relevant details can find such information either online or in various publications.

What is of interest here, however, is the manner with which Royal Engineers sought to combine the two distinctive aspects of the battery, namely the gun emplacement and the protective enclosure, in order to create a unique work of fortification with its particular design solutions and inherent limitations.

Above and below, Scale model of the Italian battleship ‘Duilio’ showing one of its two turrets armed with Armstrong 100-ton guns as displayed at the Museo Storico Navale in Venice (Image source: Author’s private collection).

The threat of naval bombardment

The necessity to equip the naval stations of Gibraltar and Malta with the heavy 100-ton guns arose from an urgent need to counter the Italian Regia Marina’s new powerful battleship armed with the same type of formidable weapons. Inevitably, and much to the alarm of the British military authorities, this development changed the whole defensive situation in the Mediterranean, particularly for Malta. For one thing, in 1874, the British had nothing afloat or on land with which to counter the power and range of these heavily armed and armoured Italian vessels. The heaviest guns then in British service were the 12.5-inch of 38 tons RMLs which were powerless to pierce the protected parts of the new Italian warships, even at close ranges. It was feared that with such powerful armament, Italian ships could destroy in quick succession all island’s fortresses, towns, and harbours, and such an attack, given the longer range of the 100-ton guns, would be achieved with relative impunity.  The threat to Malta’s defences was aggravated further by its close proximity to Italy and, consequently, the then- Inspector General of Fortifications, Lintorn Simmons, was anxious to point out in his report of 1878, the urgency of upgrading the defences of Malta with four similar guns. These, he argued, were to be best deployed along the island’s sea front to enable them to intercept ships of the Duilio class at a range of 3000 yards. Simmons warned the British government that without such guns Malta could not be considered secure.

His warnings did not fall on deaf ears and in March of that same year four guns were requested by the British government and construction was started in August, while in the meantime, the Duilio had been conducting sea trials since 1877.  These four guns which the British government bought from Armstrong were actually those that had been intended for the Dandalo. Eventually a further four were sent to Italy.

When the commanders of the fortress of Gibraltar heard of the plans to supply these big guns to Malta, they too requested some, and were quick to obtain them.  As a matter of fact, only two of the four guns ever reached Malta since the other two were shipped off to Gibraltar instead. Actually, Gibraltar was first to receive its guns while Malta received her first 100- tonner in September 1882 and by 1884 both of guns were mounted in their dedicated coastal batteries erected more or less equidistant on either side of the Grand Harbour – Cambridge Battery (sited between Fort Tigne and Fort Sliema,) and Rinella Battery placed between Fort Ricasoli and Fort St. Rocco.  The guns at Gibraltar were mounted in the Napier of Magdala Battery (so named after Field-Marshal Robert Cornelis, first Baron Napier of Magdala, an engineer officer who was governor from 1876 to 1882) and at Victoria Battery (named after Queen Victoria).

Above, View of entrance to the vaulted chambers and underground magazines at Napier of Magdala Battery, Gibraltar (Image Source: Author’s collection).

Chronology of construction

Work on the design of the 100-ton gun batteries began in 1878.  The actually construction works on the individual sites did not kick off simultaneously.  The first to be laid out was Cambridge Battery, work on which commenced on 28th August 1878. The estimated cost for both Malta batteries was £40,000. Although the date on the gate of Cambridge Battery reads 1880, the work was only completed on 27 November 1886, by which time some £18,819 had been disbursed on its construction. This was some £3,774 more than the actual cost of Rinella Battery which, moreover, had been completed nine months earlier in February of that same year. In Gibraltar both works were commenced in December 1878 and the total cost of the Napier of Magdala Battery and Victoria Battery together was £35,707.

In Malta, Rinella Battery was the first of the two structures to be actually completed even though work had commenced in 1879, that is, roughly a year after construction had kicked off at Cambridge Battery. By 5 February 1886, the official date of completion for Rinella Battery, construction costs had totalled £15,045.

This ‘gestation lag’ in the completion of the two works is important. It may, to some degree, serve to explain the adoption of the different design features and defence solutions in the execution of the two works.  During the initial stages in the design and construction of the 100-ton gun batteries in Malta, i.e., when the work on the batteries was authorized in 1878, the Commanding Royal Engineers in Malta was Col. Henry Wray, who headed a small team of engineers, amongst whom were Lt. Tressider,  Lt. H. Settle,  Lt E. Dewing, and Capt J. Davis. The War Office record plan itself, dated 1887, is signed by Col. Phillpots CRE.  By that time, however, the engineering office in Malta had gone through another two Commanding Royal Engneers, namely  Col. C.E. Cumberland, and Col. T Murrey (1879-1881). This high ‘turn-over’ of military engineers present at the seminal construction stage of these works of fortification may have to led to variations in the actual finished design product.

At Gibraltar work on the batteries also progressed in stages. The first to be initiated was Victoria Battery in 1879, to be followed by the completion of Napier Battery four years later and, likewise, the two batteries have a number of different secondary features. The plans of the Napier of Magdala Battery, dated 1885, are signed by Col  P. Ravenhill, Colonel on the Staff Commanding RE, Gibraltar, and Major C A Rochfort-Boyd, RE.


The anatomy of the 100-ton gun batteries

To the student of military architecture, the first and most interesting trait in the design of the new 100-ton batteries is the different treatment which was applied to the configuration for the two sets of batteries built in Malta and Gibraltar.

In essence, the works consisted of two main components – the gun emplacement with its magazines, and the protective enclosure, the latter also encapsulating the barrack accommodation. The latter configuration, however, was only applied to the Malta batteries.

Above, Aerial view of Napier of Magdala Battery, Gibraltar (Image Source: Prof. Q. Hughes)

Above, Aerial view of Cambridge Battery, Malta,  circa 1970 (Image Source: Department of Information, Malta).

Above, Aerial view of Rinella Battery, Malta,  circa 1970 (Image Source: Department of Information, Malta).

In all four cases, the common central feature was provided by the gun emplacement with its magazines and loading machinery.  This was the core of each battery and this aspect of the design, which was conditioned by the technical requirements of the heavy gun and its loading equipment, could not be tampered with by the engineers on site. It was controlled by the War Office and issued to the CRE in both stations.  The enveloping carcasses, on the other hand, were largely the product of the different geographical, topographic, and tactical conditions facing the engineers in their different stations. It was their job to bring the various elements together, making use of all available materials and resources, to create a functional and defensible entity.

Immediately, the most obvious difference that confronts the observer is the fact that the two Gibraltar batteries were not provided with the same all-round protective enclosures that were given to the Maltese positions. There were various reason for this but, primarily, it stemmed from the fact that the ‘Rock’ of Gibraltar was treated as one large fortress, where all the defensive works formed part of a closely-knit network of defences protected by an outer, and earlier enceinte of bastions and ramparts. Consequently, the Gibraltar 100-ton gun batteries lacked any close-in defences such as ditches and flanking devices.  In Malta, however, which comprised a much larger territorial unit, outlying works erected beyond the secure envelope of the fortified harbour enclave had, of necessity, to be provided with their own protection.  Unlike Gibraltar, therefore, the works prepared to house the coastal guns in Malta were more than just mere gun-emplacements and even though officially designated as ‘batteries’ (none of the works were ever classified as a ‘fort’ – this is a modern application ) these were, at least on paper, small self-defensible enclosures surrounded by their puny ditches and defended by flanking caponiers, and counterscarp galleries, as well as being fitted with casemated barrack accommodation and other ancillary facilities intended to house small permanent garrisons.  Still, the presence of such defensive features should not be overstated. Indeed, their application on such a small and restricted scale reveals limitations in the batteries’ overall defensive capabilities and power of resistance.

Even so, the two batteries in Malta acquired a more defined structural form than their Gibraltar equivalents, emphatically delineated as they are by a rock-hewn ditch enveloped around a pentagonal plan that conformed primarily to the conventions of the polygonal system. The two Malta batteries were fundamentally identical to each other but for the fact that their plans were inverted, thus forming a mirror image of one another. On closer inspection, however, the batteries reveal various other small, albeit significant, structural differences that indicate either the rethinking of certain ideas or perhaps the involvement of different engineers during the course of the relatively long construction process.

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Fundamentally, the Malta 100-ton batteries were designed to the conventions of the polygonal system of fortification, then the predominant style dictating the military architecture of the nineteenth century.  By the 1860s, permanent fortifications in England had adopted the system of detached polygonal forts with parapets organized for artillery, and their rears defended by small keeps, all encased in ditches covered by caponiers or counterscarp galleries. More directly, the 100-ton Batteries were influenced by the principles which British engineers began to adopt in the design of coastal batteries erected in the post-Crimean War period.  Captain A. F. Lendy’s Treatise on Fortification (or lectures delivered to Officers reading for the staff) published in London in 1862, and which served as a basic text book of sorts for the instruction of officers, gives the plan of a battery erected at the entrance of Shoreham harbour as typical of the main defensive elements and principles that British military engineers sought to adopt in the design of small works of fortification by the early 1860s.  It shows a  polygonal structure flanked by caponiers and having barrack accommodation in the gorge  – all features which are still evident in the Malta batteries 20 years later.   At Cambridge and Rinella, however, the engineers did away with the gorge keep-cum-barracks (which features had been adopted in three forts built in the 1870s at Bigemma, St Rocco, and Mosta), utilizing only the barrack function and delegating the gorge musketry defences from the keep to small counterscarp galleries. By this period, most small work of fortifications had, instead of a keep, defensible barracks in the gorge. The engineers did, however, adopt Lendy’s recommendation of shifting the caponiers to the shoulder-angles of the face rather than leaving these at the shoulder angles of the gorge as employed in the Shoreham Redoubt (see plan below). They also did away with the Carnot wall – a somewhat archaic device from the Napoleonic period that was never adopted in Maltese fortifications.

By the 1880s, the pentagonal-plan fort, in the shape of a very obtuse-angled lunette, shallow from front to rear, with shoulder caponiers and relatively flat gorge was becoming a standard design in the layout of German, Austrian, and French fortifications (see comparative diagram below).



Flanking defences

The  Malta batteries took care of their close-in defence by means of the flanking elements provided by the caponiers and  counterscarp galleries, all sunk into a low and narrow ditch,  around 24 feet deep at the counterscarp. These elements provided a degree of enfilading fire along the front, flanks, and gorge of the works. Each battery featured three caponiers and a singular counterscarp gallery.  Actually, the caponiers are best described as one full caponier (or double caponier as it is sometimes called – since it covers two faces) and two demi-caponiers (half caponiers) covering the flanks in a single direction. Both the caponiers and counterscarp galleries were protected by shallow drop ditches. The caponiers were reached from the interior of the batteries by means of underground tunnels.

The main fighting features of these small fighting caponiers were the musketry loopholes.  These small window-like openings had serrated cheeks, known as a’ redans, designed to deflect incoming bullets away from the central opening, which itself was reinforced with a small metal plate.  The loopholed plates were often precast and factory produced. Cambridge Battery also supported two loopholes (near the right caponier – see photographs) which had splayed cheeks but these appear to have been added later when the counterscarp of the battery was linked to the ditch of the adjoining Garden Battery.  Both caponiers and counterscarp galleries were ventilated by small shafts which opened onto the faces. The record plan of Cambridge Battery does reveal that its caponiers (long since demolished) had shafts which opened on the sloping roof of the structure. In both batteries, the two flanking (demi-) caponiers had  five loopholes each ( three on the flank, and two in the face), and the central caponiers, eight.

Above, View from the counterscarp showing the narrow ditch, with vertical scarp and counterscarp walls, as well as the left caponier  at Rinella Battery at the start of clearing works (Image source: Author’s private collection).

Above, View from within the ditch of the left caponier at Rinella Battery prior to restoration (Image source: Author’s private collection).

Above, Detail of the mouth of one of the musketry loopholes of the left caponier at Rinella Battery prior to restoration. Note the indented cheeks and lintel (Image source: Author’s private collection).

Above, Graphic reconstruction of loophole with serrated cheeks and lintel - known as  ‘a’ redans’ (Image source: Author).

Above, view of the counterscarp gallery and its drop ditch at Rinella Battery  – the drop ditch was designed to prevent enemy soldiers from dropping debris in front of the loopholes in an attempt to block their view (Image source: Author’s private collection).

Above, Detail from plan of Rinella Battery, showing layout of counterscarp musketry gallery and underground passage linking it to the body of the work (Image source: Author’s private collection).

Above, Detail of the mouth of one of the musketry loopholes of the counterscarp gallery at Rinella Battery prior to restoration. Note the indented cheeks and lintel. (Image source: Author’s private collection).

The caponiers were relatively very small structures by the standards of the time and provided cramped defensive positions. They were only fitted with loopholes for musketry fire and had no provisions for carronades or other heavier armament such as can be found in other contemporary forts.  Still, in 1886, Major O’Callaghan and Capt. Clarke believed these to be adequate for the defence, providing for ‘a liberally flanked ditch’.

By the time of the 100-ton batteries’ construction in the late 1870s, military engineers in Malta had only employed the concept of caponiers once at Fort St Lucian ( 1874-1878) and would employ them again only on three other occasions in the course of the nineteenth century: namely, at the Dwejra entrenchment (begun in 1881)  which was fitted with a singular caponier; at Fort Tas-Silg (begun in 1879 -1883) which was fitted with three such features; and at Delle Grazie Battery (begun in 1889) which was defended with two caponiers.

None of the 100-ton gun batteries, in fact, made any provision for the mounting of  carronades or other forms of heavy defensive ordnance, thereby rendering the works’ power of resistance against landward attack rather weak and of limited duration. The defensive effort would also have been severely handicapped by the small size of the detachments garrisoning the batteries. It would appear that in their defensive mode, the 100-ton gun batteries were only expected to hold out against small enemy detachments intent on silencing the batteries in the course of surprise attacks.

Above, Interior view of the left caponier at Rinella Battery prior to restoration (Image source: Author’s private collection).

Above, detail of the of the two musketry loopholes with splayed cheeks  along the right flank of Cambridge Battery, close to the caponier (Image source: Author’s private collection).

Against landward attacks by a larger and determined enemy forces, wielding even the smallest of field guns, however, the batteries would have had little hope of resisting for any substantial length of time.  However, both batteries could be supported by gun fire from neighbouring forts, particularly by the guns on the land front of Fort Ricasoli (in the case of Rinella Battery – the Left Ravelin) and those at Fort Tigne and Fort Manoel in the case of Cambridge Battery. Still, this is assuming that the adjoining forts themselves would not have been preoccupied with their own defence.  All in all, these features and limitations show that  rather than independent ‘forts’, the 100-ton gun batteries in Malta were still inherently subservient elements in a wider strategic deployment of defensive positions.

A study of the four batteries shows that their designers’ main and overriding concern was the need to protect the guns and their crews from direct naval bombardment. Indeed, like most coastal batteries, these works were primarily intended for a distant artillery fight, and most of the defensive effort was channelled to address this principal concern.  As a result, the works were heavily protected on only three of their four sides, i.e., the fronts and flanks facing the sea, all of which would have been in the path of incoming shells fired from naval vessels. This protection, as in most fortifications of the period, was achieved by the application of thick protective parapets of earth and concrete.

Above  View of the breach created in the left flank of  Rinella Battery’s scarp, exterior slope revetment and terreplein prior to restoration (Image source: Author’s private collection). This was caused when the battery was hit by aerial bombs during WWII.

Above , Close-up view of the breach created in the left flank of  Rinella Battery’s scarp, superior slope revetment and terreplein prior to restoration. Note the partially rock-hewn base of the scarp. (Image source: Author’s private collection).

The gorge of all the batteries is devoid of such protection, and in the case of the two Malta batteries, the resultant form gives the impression of a truncated structure, whereby the rear parapet is replaced by a relatively thin masonry wall fitted with musketry loopholes. This effect is more evident at Rinella Battery, since Cambridge Battery still retains the superior slope of a thick earthen parapet.  In both batteries, the inner side of the barrack range is also shielded by an earthen massif, in the fashion of a parados, designed to screen the living quarters form shells plunging in from the direction of the sea.

Another element which helps stress the overriding concern of the defensive layout comprises the two barbette positions that crown the flanking cheeks on both sides of the centrally-mounted guns – traverse-like features revetted in masonry on their exterior inward slopes. Originally, these were intended to house the Direction Range Finder posts but in the event of an attack, these would have doubled up as infantry rifle pits, providing the garrison with elevated defensive positions against enemy troops approaching the battery from both the seaward direction and flanks. However, owing to their open gorge, they offered no protection to their occupants in the event of a landward attack. These were eventually found to serve no real purpose and were filled in with earth to increase the protection of the chambers beneath.


The minutiae of design and construction

Aside from the inverted plans, there were other significant secondary differences in the designs of the two Maltese batteries. As already mentioned earlier, these differences, at times marked, but often subtle, may perhaps result from the fact that work on the two batteries did not proceed simultaneously and could have been influenced by the input of different engineers.  In many ways, the design and layout of Cambridge Battery is a marked improvement on that of Rinella Battery. The thin loopholed musketry parapet crowning the gorge of Rinella Battery (which is lacking in Cambridge Battery), for example, may have been considered necessary owing to the fact that the windows (doubling as musketry loopholes with the addition of armoured shutters) opening up from within the barracks along the gorge of the work were situated so low within the ditch that they were ineffective.  Hidden away as they were from view by the higher counterscarp of the narrow ditch, they could not allow the defenders to fire their small arms at an investing force. Indeed, this quirk in the design, rendered any musketry defence of the approaches to the fort along the glacis totally impossible. In other words, the battery was virtually ‘blind’ and unprotected along its gorge – hence the need for the additional musketry parapet along the crest of the gorge. This parapet, however, is a relatively thin and weak wall, and was so low that soldiers could only fire their muskets kneeling down.  This defect seems to have been corrected at Cambridge where the ‘windows’ of the barrack accommodation along the gorge were built much higher up the scarp  in the form of horizontal loopholes reinforced with metal plates. This was definitively an improved design feature when compared to the rather crude arrangement of pivoting metal plates employed at Rinella – an arrangement that has all the hallmarks of an after-thought and improvised solution.

The types of loopholes used in the specific conditions provided by the two batteries do not adhere to the maxims generally adopted in the design of ditches. As a rule of thumb, horizontal loopholes were generally recommended for use within a ditch and vertical ones outside – the same advice is given by Lendy:

‘…horizontal [loopholes]… [are] rarely employed except for the defence of a ditch in the galleries of reverse and caponiers, where a wide horizontal range is required’.

However, this is exactly the opposite of what we find along the gorges of both Cambridge and Rinella batteries. Even the loopholes in the caponiers and counterscarp fail to follow this rule. This is something, however, which is encountered in many other British forts erected in Malta at the time. The use of horizontal loopholes inside ditches, in fact, was more the exception than the rule. The few instances where it was actually applied can be seen in the caponiers of Delle Grazie Battery and in the perimeter defence posts of Fort St Rocco.  The preference for vertical loopholes may have arisen from the fact that more vertical loopholes could be fitted into any given length of wall than if horizontal ones were employed,  thereby maximizing the defensive firepower.

Above, Detail of scarp of Rinella Battery along gorge showing one of the barrack embrasures and the musketry parapet with loopholes along the gorge of the work after restoration (Image source: Author’s private collection).

Above, Detail of the loopholes in the musketry parapet along gorge of Rinella Battery prior to restoration (Image source: Author’s private collection).

Above, Detail of armoured metal shutter (in open position) pierced with two loopholes, after restoration (Image source: Author’s private collection).

Above, Detail of horizontal loophole opening from the barracks along the gorge of Cambridge Battery  before restoration (Image source: Author’s private collection).



The Gateways

Another defensive feature found at both Cambridge and Rinella Batteries , but missing in the Gibraltar batteries owing to their lack of defensive perimeter, was the gateway with its guardrooms and drawbridge. At both Cambridge and Rinella this was situated in the gorge of the work and was served by a Guthrie Rolling Bridge.  At Rinella the entrance was approached down a curved and sloping road cut into the glacis to the rear of the battery, in the form of a ‘reverse’ ramp, i.e., sloping downward towards the fort to expose the path to the full view of the defenders.

From an architectural point of view, these gateways represented the sole decorative element in the design of the two works of fortification, even though, as in most gateways of British forts of the period, this was limited to a simple arch decorated with some bossing or rustication, either in the voussoirs, or the flanking pilasters, or both. The two leaves of the gate opened inwards and were armour-plated on their outer faces. Loopholes in the gate itself enabled the defenders to cover the drawbridge and the immediate approaches to the entrance with musketry fire.

Front elevation of main gate of Cambridge Battery prior to restoration (Image source: Author’s private collection).

Front elevation of the original main gate of Rinella Battery prior to restoration (Image source: Author’s private collection).

Armoured main gate of Rinella Battery prior to restoration (Image source: Author’s private collection).

Again, the facades of both gates differ considerably in detail. That at Cambridge Battery has significantly wider side pilasters and projects slightly outwards from the main wall.  It is interesting to note that the façades of both portals have no bases, thereby leaving the gateways unceremoniously ‘hanging up’ in mid-air.

The drawbridges employed in both Malta batteries were of the Guthrie Rolling bridge type.  Invented by C.Y. Guthrie, this was one of the most widely used drawbridge mechanisms in British forts of the period as it was considered to be the best of all forms of drawbridges. Basically, it consisted of a plank placed across the ditch which could be pulled back when it was desired to disrupt the communication. It was made up of two main components, the bridge platform and the movable arms or struts which accompanied the bridge in motion. The following is a description of the rolling bridge taken from Mr. Guthrie's paper in the R.E. Professional Papers, Vol. XIII:

‘The bridge is formed of two rolled or built wrought iron girders covered with planking and supported at their centres by cast iron struts: these are suspended by links in such a manner that while the upper end of the struts accompany the Bridge in its motion, the lower ends travels nearly vertically against the escarp wall. Thus their centres of suspension, which are also their centres of gravity, descend in circular arcs, while the upper ends which support the bridge ascend in arcs of a certain curve. The weight of the struts is thus opposed to the weight of the bridge, and the position of their points of suspension, their angle of inclination and weight, and the form of the racers against which their lower ends travel, are such that they balance the weight of the bridge in every possible position. It follows from this that the force required to move the bridge is exceedingly small, being due only to the friction on the axles.’

To run the bridge in, the door of the fort was opened wide and the bridge was pulled in by means of a rope. This raised the inner wheels of the bridge up the inclines of the granite sill and at the same time the outer end was displaced from the lip of the outer sill. When the inner wheels were pulled up they immediately engaged the rails and the weight of the lifting arms assisted the raising of the bridge. As the bridge was driven back into the gateway the arms continued to retract backwards until they reached a vertical position at which point they disengaged from the bridge. To run the bridge out again it was necessary to push it along its rails. The bridge then would move outwards in a horizontal position. As the bridge continued to move out-wards its weight would cause it to descend and settle down on the supporting sills with the lever arms fully extended  (for further reading on the Guthrie Rolling Drawbridge go to illustrated article by David Moore at http://www.palmerstonforts.org.uk )

Photograph showing the Guthrie rolling bridge, practically complete with hand rails and platform, still insitu at Cambridge Battery (Image source: Author’s private collection).

Above and below, Two views of the retractable arms of the original Guthrie rolling bridge when still in situ at Cambridge Battery. This was dismantled and removed to Rinella Battery some years ago (Image source: Author’s collection).

Barrack Accommodation

An important feature of the Malta batteries, unlike the two in Gibraltar, was the row of casemated barrack rooms with guard rooms which were inserted into the gorge of the structures. These small vaulted casemates were lit through windows which were designed to serve also as musketry loopholes.  Both Malta batteries had additional rooms opening onto the vaulted entrance passage way and designed to accommodate cookhouses, washrooms, and latrines.  All four batteries contained a number of  casemates well protected within the core of the structure. At ground level, these vaulted casemates opened directly onto a courtyard immediately to the rear of the gun emplacement and were meant to house the machinery (pumps, engine, accumulators and coal)  that was required to generate the hydraulic power necessary to work and load the gun.  In both Malta batteries, a water tank, for collecting rain water was cut into the ditch.  At Victoria Battery a concrete channel was placed at the foot of the apron, which occupied an area of some four thousand square feet in front of the gun, to direct all the surface rainwater into a 6,062 gallon tank for use in the pneumatic system.


The Gun-emplacement

The common feature throughout all four batteries was the method of mounting and arming the 100-ton gun.  In all instances the guns were mounted en barbette on a wrought iron traversing carriage, roughly in the middle of the battery, behind a concrete parapet 8 feet high and fronted by a thick concrete ‘glacis’,  and protected on both sides by high revetted cheeks that served as shielding traverses. The concrete apron in front of the guns was eventually found to be rather problematic. In 1887, a report on the parapet of Cambridge Battery, drew attention to the fact that the crest of its exterior slope rose 4 feet above the crest of the external earthen glacis, and this, when seen from afar, showed clearly as a marked white band which distinguished the battery from its surroundings:

‘ ... the concrete surfaces thus exposed to view owe their extreme visibility to the smoothness of their planes as contrasted with the rough surface of the natural rocks, or the comparatively uneven and discoloured faces of the neighbouring walls. ‘

Earlier in 1886, O’Callaghan and Clarke had been likewise concerned that these concrete slopes were rendering the Malta batteries ‘unnecessarily conspicuous’. However, they believed that this defect was ‘capable of improvement’:

‘Both at Rinella and Cambridge the exterior crest of the concrete parapet was 4 feet above that of the glacis. This gives a marked white band, which at once distinguished the battery from its surroundings, and directs attention to the gun. Added to this, the exterior slope is about 8 1/4 o, and the parapet   …. 44 feet thick on the centreline, with a height at Rinella of only 72 feet at the crest, another clear white band is placed on top of the first reflecting light at a different angle, and adding greatly to the visibility of the battery and gun. Since a 100-ton gun need hardly be called upon to defend its own glacis, which, moreover, being in front of a liberally flanked ditch , requires no special protection, the creation of a visible exterior slope may usually be avoided in such a case. The concrete surfaces thus exposed to view owe their extreme visibility  to the smoothness of their planes as contrasted with the rough surfaces of the natural rocks, or the comparatively  uneven and discoloured  faces of neighbouring walls. It would be almost impossible to mask the concrete surfaces by any sort of vegetation, and their extreme hardness will prevent weathering within a reasonable time. We suggest, therefore, that the uniform  whiteness of the surfaces visible from the sea should be broken up by painting them with brown blotches roughly imitating the natural rock. In addition, it appears desirable to break the even line of the crest of the glacis.’


Above, Diagrams from the 1886 report illustrating the alterations recommended to be made in the batteries (Image source: Author’s collection).

In the Gibraltar batteries, however, the situation was different. The concrete parapet of the Napier of Magdala Battery was hidden from view as it had been kept below the level of the natural ground, while that at Victoria was hidden behind a thick earthen parapet that was built up in front of it. As a result, the superior slope in front of the concrete was well grown over with vegetation while the wings on the flanks were covered with a luxuriant growth. On the other hand, the concrete slopes limiting the training of the guns on either side stood out glaringly visible at long ranges drawing attention to the battery from the sea. In attempt to offset this defect, the engineers planted Ivy creepers  but O’Callaghan and Clarke expressed doubt if this would ever spread over the sun baked concrete surface.

Instead, they urged that the concrete be cut away and replaced by earth given that the concrete was seen to afford little effective protection. Indeed,  they also feared that the concrete surface would in fact only serve to hold the point of the projectile  and turn it down into the battery, which an earth covering would not do. This opinion which was also shared by the commanding officers of the Royal Artillery and Royal Engineers. They also suggested that the small portion of concrete left round  the loading turret should be coloured a greenish brown, dabbed on irregularly. At the same time it was suggested that the slopes on the flanks of the emplacements were to be cut down and made good with earth. These slopes were seen to serve no useful purpose, and the near portion of them being liable to be hit, showering the interior of the area with lethal splinters.

In Malta other slight alterations were made in 1896 when the stone revetments of the cheeks flanking the battery were removed to expose their earthen slopes.  Eventually, large areas of the concrete glacis were removed and replaced with earth. The record plan of Cambridge Battery, shows that this alteration had been implemented by 1890.

Above and below, two views from the rear of the 100-ton gun-emplacement at Napier of Magdala Battery (Image source: Author’s private collection)

Above, Experimental gun emplacement erected for trials at the proof buts in the Royal Arsenal at Woolwich (Image Source: The Engineer – 24.9.1880). Below, The 100-ton Armstrong gun  and its ammunition (Image Source: The Engineer – 24.9.1880).

Above, The 100-ton gun newly installed in a still incomplete Napier of Magdala Battery at Gibraltar ( Image source: Q.Hughes).

Above, The 100-ton at Cambridge Battery before it was cut down for scrap metal (Image source: Author’s private collection – part of Q. Hughes personal collection given to the author).

Above, A restored 100-ton Armstrong gun at Napier of Magdala Battery, repainted light grey (Image source – Author’s private collection).

Above, Diagram showing the loading mechanism and graphic reconstruction of underground chambers and magazines by the author.

The gun-platform was pivoted on a heavy mass of cast iron set in the concrete floor of the emplacement over which sat a revolving drum of strong wrought iron which was bolted to the lower surface of the platform. An outer steel racer served the two trucks supporting the rear of the slide. The gun and its platform were rotated by means of four hydraulic pistons, set in trenches in the floor of the emplacement, which acted on chains wound round the turntable. The platform could be traversed through 180 degrees and elevation was achieved by means of two hydraulic jacks below the barrel. Only eleven degrees of elevation and depression were possible by this means.   .  


Underground magazines and loading mechanism

In general, the arrangement of the internal core was similar in all the four batteries. Beneath the gun and around it stood the magazines and loading apparatus.  Twin underground loading passages led to the two hoists, one on each side of the gun, while railway trucks carried the shells and cartridges, which were stored in separate central compartments, to the lifts which conveyed the ammunition to the muzzle of the gun. Initially, the shell stores were intended to house  only 33 shells but these were eventually upgraded to store  87 shells, while 107 cylinders were held in the adjoining cartridge magazines.

Above, detail from 1886 report showing O’Callaghan’s and Clarke’s joint recommendation for increasing storage capacity in battery’s shell magazines (Image source; Author’s private collection).

The two munitions stores were mounted centrally within the battery and placed just to the rear of the gun emplacement beneath the open courtyard. Surprisingly the thickness of  overhead concrete protection covering these magazines – perhaps the most sensitive part of the whole work and the part requiring most protection -  is somehow the shallowest in all the battery!

There were two loading turrets, one on either side of the emplacement, each cylindrical in shape, about 11 feet in diameter and protected by armour plates. The porthole was closed by a counterweight shutter or port-stopper which was pushed open by the muzzle of the gun as the latter was being depressed to the loading position. In the loading position, the muzzle of the gun rested on a muzzle rest, which stood about 5 feet outside the loading turret.

Above, View of the right loading chamber with narrow gauge rails for loading trolleys at Rinella Battery. Below, one of the two turntables at Rinella Battery (Image source: Author’s private collection).

Above, View of the lift shaft at Rinella Battery prior to restoration (Image source: Author’s private collection).

Above detail of the original port-stopper (a counterweighted shutter) at Napier of Magdala Battery in Gibraltar. This was designed to protect the mouth of the porthole of the armoured loading chamber through which the gun was loaded with gunpowder charge and projectile. Below, Detail of the original  rammer (Napier Battery) which pushed projectile and charge into the barrel of the 100-ton gun (Image source: Author’s private collection).

Above, Muzzle rest at Napier of Magdala Battery, designed  to align the barrel of the 100-ton gun directly with the porthole in the loading turret (Image source: Author’s private collection)

The ammunition hoists lifted the shell and charge up a thirty foot shaft to the level of the floor of the loading chamber by means of a hydraulic piston,  which worked, in the words of Maj. J. F. Lewis R.E.,  much like ‘a lift in an hotel’:

‘The complete charge, cartridge and projectile, is placed on a special truck, run onto the top of the hoist, and turned into the proper direction. It is then raised to the muzzle of the gun, and rammed home off the truck.’

The loading trolley consisted of a wooden cradle capable of holding one complete round inclined at an angle of 11 degrees to enable the axis of the charge to be aligned with that of the barrel of the gun in its depressed loading position. Each ammunition passage had two sets of rails converging on a turntable at either end so that two trolleys could be used at the same time; while one was being loaded the other was being charged. The heavy projectile was lifted onto the trolley by Weston's differential pulleys that ran on an overhead traveller leading from the shell room to the ammunition passage. A powerful rammer, with a wooden stave 45 ft long and worked  by three hauling cylinders ( two for ramming and one for withdrawing)  drove the charge, gas-check, and shell from the loading chamber into the bore of the gun.

The batteries were also fitted with lightning conductors.   O’Callaghan and Clarke suggested that the system formed by the suspenders and rails for the travellers in the shell room and loading passage was to be connected with the earth for the lightning conductors while the suspending bars projecting from the vaulted roof which had been intended for similar travellers in the cartridge storerooms, (which travellers were never installed as they were found not to be required) were to be cut off.  One significant defect of the underground chambers in the Malta, particularly the ammunition passages, was that these were poorly lit. The underground chambers  depended on their light solely on the lamps which were put in from the lighting passages along the sides. As a result, during ‘loading, it was found necessary to supplement the lighting by lanterns, which were carried about [inside the loading passage] and held in the position required ‘ - a dangerous procedure which obviously negated all the in-built safety precautions that came with magazines. The 1886 report recommended that additional windows for lanterns were required  ‘at the point where the travellers deliver[ed] projectiles to the loading trolley, and also at the lift itself’.  At the Napier of Magdala Battery, the situation was slightly better since these inner passage received light during the day through the door at the end  of the passage where it opened out to the courtyard at the rear of the battery.


Method of Construction

Up until the mid-nineteenth  century, fortress-building in the Mediterranean was largely a matter of building in local stone. By the 1870s, however, the British were employing concrete in their works of fortification.

The 100-ton gun batteries employed a hybrid combination of masonry and cast-in-place mass concrete elements in their construction. The overall product, however, still retained a masonry ‘feel’ and texture.  In all four batteries, the main body was created through a mixture of techniques involving partial excavation of the bedrock (cut-and-bury techniques) combined with masonry construction and concrete bracing and revetments.

Above, View of the scarp along the gorge of Cambridge Battery prior to restoration (Image source: Author’s private collection).

Above, View of the scarp and gateway along the gorge of Cambridge Battery prior to restoration (Image source: Author’s private collection).

Above, View of the gorge scarp of Rinella Battery prior to restoration (Image source: Author’s private collection).

Above, Detail of the masonry revetment of the exterior slope and concrete revetment of the upper part of the scarp along the right flank of Rinella Battery prior to restoration (Image source: Author’s private collection).

In the Malta batteries masonry was employed in walls and vaults, and in the facing of the exterior slopes of earthen parapets. External facades were built of rusticated masonry – drafted blocks with flat bossing in low relief (known in Maltese as ’bunja’) –  while secondary and interior walls were constructed of smooth-faced ashlar.  In most cases, the softer Globigerina Limestone was employed while a harder quality stone, the Coralline Limestone, was often employed in capstones of the exterior slopes of revetments. Often, hardstone was also employed for decorative effect in some elements of gateway facades and quoins, such as at Cambridge Battery where it is employed in the base of pilasters.  In Gibraltar, masonry elements were likewise employed, although the qualities of the Gibraltar limestone – a greyish-white or pale-grey compact, and  sometimes finely crystalline, stone – were different from the yellowish grainy nature of the Maltese stone, thereby imparting a different feel and texture to the structures.

Concrete, on the other hand, was employed rather haphazardly and largely as a  covering, both on superior slopes of parapets and in the revetment of  the scarp and counterscarp walls. It is best preserved on the superior slope of the ‘glacis’, or apron, on the front seaward side of the 100-ton gun batteries, beneath the guns (where not cut away for the reasons mentioned earlier). In the 100-ton gun batteries the concrete used was un-reinforced and cast in lifts of approximately the same height. As shown by the photograph below, revealing a cross section of the counterscarp of Cambridge Battery, the thickness of the concrete revetment is around two metres. Stone headers or bond-stones are also visible along most of the scarp and counterscarp concrete revetments, although their real purpose is not yet fully clear.

Above, Detail of section through concrete counterscarp revetment at Cambridge Battery, prior to restoration (Image source: Author’s private collection).

Above, Detail of concrete scarp at Rinella Battery, prior to restoration, showing exposed aggregate and traces of surface cement rendering (Image source: Author’s private collection).

Above, Detail of concrete revetment along counterscarp of right flank of Rinella Battery, prior to restoration. Note the masonry headstones inserted into the layered concrete aggregate (Image source: Author’s private collection).

The concrete walls do not have any expansion joints although, in various places, and at somewhat irregular intervals, these are perforated with small rectangular holes, particularly at the horizontal interface, or base, of the concrete wall and the underlying masonry or bedrock. This seems to suggest that the openings served as weep-holes rather than as anchor points for formwork ties.  Most of the concrete revetments in the Malta batteries from the 1880s have lost their smooth cement surface finish (owing to deterioration), to reveal cast layers of hardstone aggregate of non-uniform grading. A significant proportion of this aggregate is quite elongated and the proportion of the aggregate appears rather low. Similar method of concrete construction can be found in the walls or ditch revetments of Fort Mosta, Fort Bingemma, Fort San Leonardo and the Dwejra lines. Further studies, however, are necessary to establish the actual concrete strength, which, a prima facia does not appear to be high, with the overall density (i.e. the mass per unit volume) being probably lower than that of the masonry elements used in the same structures.  The counterscarps are also largely revetted in concrete, except for a few areas along the gorge.

Above, Detail of concrete revetment along counterscarp of Rinella Battery, prior to restoration, showing the exposed concrete aggregate and inserted headstones (Image source: Author’s private collection).

Above, Diagram showing a typical sectional view through rampart along flanks of Malt’s 100-ton gun batteries (Image source: Author).

It was only along the wall at the gorge of the batteries that concrete was not employed at all in the construction of the scarp. Here, the facades were built entirely of stone except for the lower third which is carved out of the bedrock. This special treatment mainly arose from the fact that the gorge elevations presented the principal façade of the batteries. Here, the British military engineers sought to imbibe their creations with some degree of architectural character.  Notwithstanding, the overall treatment still fails to impart any sense of aesthetic gravity.

Other elements constructed in masonry were the internal courtyard walls and parapets, and the underground vaults and magazines. The underground magazines were very well aerated and  detached from the damp bedrock along the sides by means of enveloping lighting passages.


Above, Detail of the rusticated masonry finish along the ‘barrack’ face at the gorge of Rinella Battery prior to restoration. Note the relatively large weep-hole at the junction of the bedrock and wall. (Image source: Author’s private collection).


The Parapets

An important protective element in all of the batteries was provided by the thick earthen mounds which comprised the parapets and upper elements of the structure along the flanks and rear. These earthen massifs were considered an important component in the defensive work’s ability to absorb the kinetic energy of explosive shells. In Malta, this terreplein, or remblai (which was often obtained during the excavation of the ditch), was a rather coarse, dry mixture of stone chippings (varying considerably in size), combined with earth and soil. Along the flanks of the two Malta batteries, the thick earthen parapets were revetted with a masonry skin of hardstone capstones, laid in an inclined plane on the exterior slopes, a technique which was first employed in Malta on the Corradino Lines begun in 1872. Such a covering helped keep the earthen fill in place, and prevented it from being carried down into the ditch below by torrential downpours.

By the mid-1880s, however, military engineers had learnt not to look at soil or earth alone as a source of protection against bombardment. Around 1886 it was found that even a moderate quantity of earth over a casemate increased the explosive effect of a shell by “tamping” it, that is, by preventing the force of the explosion from being wasted in the open air. Most forts from this period had enough earth over them to tamp the shells thoroughly, but not enough to prevent them from coming into contact with the masonry elements of the casemates below and the latter was not thick enough to resist the explosion of the big charges (the penetration of projectiles varied according to the nature of the soil—the lighter the better for protection. Sand offered the greatest resistance to penetration, clay the least).  Later fortress designs would eventually have the tops of casemates either uncovered, or covered with only a few inches of earth over them, in which grass was encouraged to grow for concealment. By the 1890s, many European engineers were growing increasingly of the opinion that bare concrete surfaces offered the best resistance.

The design of the 100-ton gun batteries appears to show that British engineers were already thinking along such lines by the late 1870s although in this case,  concrete protection was reserved largely for the massive frontal apron protecting the gun. This, however, was not designed to resist high angle fire (which would soon become a deadly threat to most forts as revealed by the experiments held at Fort Malmaison in France in 1886 )  but only provide a barrier against a relatively flat trajectory.   The casemated magazines themselves, situated immediately to the rear of the gun, were only given a few feet  of overhead concrete  protection. Actually, O’Callaghan and Clarke were weary of fully exposed concrete surfaces which, they believed, would only serve to turn the point of incoming shells and direct them into the battery and they even went on to propose the removal of some of the concrete surface and their replacement with earth.

Camouflage and the 1886 evaluation

The report on the 100-ton guns at Gibraltar and Malta written by O'Callaghan and  Clarke, dated 13 April 1886, is an important document as it reveals the initial teething problems which developed in working the gun and the defects in the design of the batteries. Both were present at RineIla Battery during the firing practice and their observations and recommendations were eventually to lead to a number of improvements in the system. Amongst the improvements to structures which they recommended, was the need to hide the concrete surface of the aprons with brown blotches of paint in order to mimic the surrounding natural terrain.  Notwithstanding, in 1888, Lt-Gen. Sir Lothian Nicholson and Maj.-Gen. Goodenough C.B. still found the apron of Rinella Battery somewhat conspicuous from the sea:  ‘ ... much more so than the other 100-ton gun emplacement at Cambridge. The concrete parapet still showed as a broad white line between two dark green bands, indicating that the camouflage paint recommended by O'Callaghan and Clarke had not been applied. Even the gun was found to shine in the sun and so it was proposed to distemper it.  By 1890, Lewis quotes it as a successful attempt in camouflage in his manual for Royal Engineers: ‘ The 100-ton guns at Malta’, he wrote, ‘ have been rendered very inconspicuous by having been painted a light grey, which harmonizes with the stone fences about them’.   In 1886  O’Callaghan and Clarke reported that both guns had been ‘painted with excellent results. Seen from the sea, even when in the loading position’ they showed ‘ but little against a background of walls of nearly similar colour’ – they do not, however, specify the colour.  At Gibraltar, on the other hand, the guns were at the time painted  black and the commission recommended that these were to be repainted a ‘greenish-brown, dabbed on irregularly’ to help them blend into the terrain.

Above, The gorge of Victoria Battery around 1890. Note the rampant vegetation on the superior slopes of the earthen cheeks on either side of the gun emplacement. This was encouraged to grow to help break up the distinctive profile of the battery when seen from afar (Image Source: Q. Hughes).

This need to hide the battery from view also saw the military engineers attempt to cover, or shield parts of the battery with shrubs and other forms of vegetation. Endemic vegetation was encouraged to grow on the exposed surfaces visible from out at sea.  Coupled with the paint jobs designed to temper the concrete, these attempts can be considered as an early form of camouflage, a defensive visual technique that would come to form an indispensible part of the modern fort in subsequent decades.


To be continued (Part II).

Dr. Stephen C Spiteri PhD (C)2011



Full references and sources will be provided in a forthcoming publication dealing with British Military Architecture in the Mediterranean, currently under preparation.


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100-Ton Gun batteries of Malta by Military Architecture
100-Ton Gun batteries of Malta by Military Architecture



Dr. Stephen C Spiteri

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