Canadian Historic Sites: Occasional Papers in Archaeology and History No. 15

A History of Martello Towers in the Defence of British North America, 1796-1871

by Ivan J. Saunders

Historical Background

The appellation "Martello tower" is correctly used to describe some 200 thick-walled, round, stone or brick, permanent defensive works erected in many parts of the British Isles, at the Cape Colony, and in British North America and the United States between the years 1796 and 1850. All had the common distinguishing features of a squat appearance, flat roof, a high scarp wall and limited means of entry, although their adaptation to meet a wide variety of defensive needs produced a great variety of structural detail. Most of these Martello towers were constructed in Great Britain between 1805 and 1812 to resist a threatened Napoleonic invasion, and both the name and common appearance of these works were popularized by those erected along the south coast of England. Martello towers were the most popular and enduring type of work in this era of British imperial fortification.

The Martello towers constructed in British North America between 1796 and 1848 displayed few functional differences, although individually they were marked by a profusion of detail adapting them to the local circumstances of their construction and to the peculiar military demands of the times. The sixteen Canadian towers were constructed at four principal British American strategic points: five at Halifax; one at Saint John, New-Brunswick; four at Quebec City: and six at Kingston. The first of them were begun or completed before the end of the Napoleonic Wars in 1815. The six at Kingston, much more complex in design, were constructed in 1846-48 in the wake of the Oregon crisis. None of the towers was ever subjected to attack and of the sixteen, eleven remain today in testament to the durability, if not necessarily the military efficiency, of the design.

Although most of the Canadian towers are directly derived from the design of towers erected along the south and east coast of England between 1805 and 1808 or from the standardized towers accepted into British fortification theory after 1815, the antecedents of the original design and, in fact, the origin of the name Martello itself are matters of some conjecture. This whole issue is of special importance in the Canadian context as three of the British North American towers located in Halifax predate by several years the name or even the specific concept of the Martello towers erected in England to resist Napoleon.

Strictly speaking, the name "Martello tower" applies to the ovoid or circular brick coast defence towers erected in the British Isles in the Napoleonic era. The name itself was first popularized in that context in England after 1803, and was derived from a stone tower on Cape Mortella in Corsica which was valiantly defended against English naval attack in the years 1793-94.¹ In the first instance the name referred to a quite specific design, but it has been corrupted subsequently to include many types of masonry tower fortification. This is particularly true in 20th-century literature, where the term has degenerated into a convenient, if often misapplied, descriptive catch-phrase.

The characteristic English Martello tower was a circular masonry structure two storeys high, with a terreplein on top designed to take from one to four guns. It varied in exterior top diameter from 35 to 55 ft., depending on the number of guns to be mounted, and was from 30 to 35 ft. in height. It had a bombproof arch above its second storey covered in masonry to the level of the terreplein and sustained at the centre by a masonry pillar, The platform was surmounted on its periphery by a parapet some 6 ft. in height with a banquette step all round. The upper interior storey was fitted as a barrack floor and the lower contained a magazine and storage facilities. The characteristic entry to the tower was by a door in the upper storey, reached by a moveable ladder or drawbridge.² In essence these English towers were elevated gun platforms, high enough to make escalade difficult, and capable of independently housing and defending their garrisons against all but a sustained regular attack assisted by artillery. All of the Canadian towers fall within this functional definition, and all but the first three Halifax towers are structurally compatible with it.

While the name Martello can be traced satisfactorily to a Corsican origin, the same is by no means true of the design. It appears, in fact, that the Italian Mortella tower was a weak and primitive structure distinguished more by circumstance than any intrinsic merits of its construction. In the English context, at least, it appears to have done little more than popularize the general virtues of towers within the military establishment, as the important engineer officers at its siege were not directly involved in the design of the English towers and some retained reservations about their use. A much more convincing case for the antecedents of the English Martello towers can be made by considering the construction of a number of basically similar towers on Minorca which the English occupied in the years 1798-1801,³ and by the impetus provided by the French invasion scare of 1803-05 to find some cheap, functional and reassuring means among the possibilities then available of defending the threatened coasts. This may explain the development of the English towers, but it by no means elucidates the origin of the Minorca towers of 1798, or, more importantly, the genesis of the first towers that were begun at Halifax or Cape Colony in 1796.

There are no readily attributable English precursors for such towers. Masonry towers as outworks, and more particularly as adjuncts to major fortifications were a normal feature of medieval fortification in northern Europe, but with the increase in the power of artillery they fell into disuse. A distant relative of the early 19th century towers can, perhaps, be discerned in the coastal defences erected by Henry VIII after 1538, in fear of an invasion inspired by the papacy. They were the most extensive coastal works erected in England before the 19th century, and featured isolated castles with round stone towers as keeps.⁴ The proportions and function of these towers, however, can not be equated with those of the 19th century towers, and they can not be said to provide any direct link. The paucity of towers in English artillery fortification is indicated by the fact that one must look forward to the period of the American Revolution for the next instance of their use.

At that time, in fear of a French naval attack, it was proposed to build 30 round coastal defence towers on the exposed Channel Island of Jersey. Construction began in 1779, and 20 had been completed at the time of the Cape Mortello incident in 1794. All were respectable stone works, although lacking some of the characteristic features of Martello towers. They were followed after 1783 by the construction of 15 small and inferior battery support towers on the nearby Island of Guernsey. They were better adapted to guard duty than to providing any real measure of military defence, as each was only 20 feet in diameter with four-foot-thick walls. They were intended to be equipped with Coehorn ordnance, but were never armed. After the war, in 1787, they were examined in detail by a committee of engineers who concluded that:

In consequence of their circular figure and smallness of their diameter, the fire from the Crenaux, or even from the top is very inconsiderable. . . for the security of the lesser batteries, we approve of towers, but would recommend a different construction.⁵

Although it is evident from the above and other circumstantial evidence that there were within the Corps of Royal Engineers supporters of and even enthusiasts for the use of towers as detached works, it is equally certain that no single satisfactory design had been settled on.⁶

As the Channel Island towers were the only similar works erected in the British Isles before the enthusiastic spate of tower building that scattered well over a hundred such structures along the British coasts between 1804 and 1812, we must seek elsewhere for their direct precursors. Contemporary North European influences are difficult to discern and a more fruitful source of inquiry devolves on southern Europe. There, in the Mediterranean and Black Sea areas, particularly in the areas under Genoese influence where different conditions of warfare prevailed, isolated stone towers were a common means of defending the sea coast against marauding pirates and privateers:

The fiat shores of the Roman Campagna had been defended in this manner since the fifteenth and sixteenth centuries: there were similar towers in Minorca; and in Corsica there were 85 such towers built at varying periods on prominent points overlooking the sea.⁷

It was certainly one of the latter towers that was defended so spectacularly by the French in 1794. It appears likely that the pre-existing Minorcan towers, in part at least, inspired Captain Robert D'Arcy of the Royal Engineers to undertake his building programme there in 1798.⁸ Little is known of the origins of these towers and, bereft as the above descriptions are of structural detail, it is impossible to trace in them an evolutionary trend leading to the established pattern of the British gun towers as drawn up by Colonel Twiss and Captain Ford in 1803.

Thus the specific origins of the three towers erected at Halifax in 1796-98 under the direction of Prince Edward, the Duke of Kent, are a matter of conjecture. They may well have owed their inspiration to the Corsican towers, but in their essentially similar design and some of their more salient structural features, they appear to diverge both from what is known of the Mediterranean towers and from some of the immediate influences that went into the early English type. Their pattern may have been derived either from some general or specific body of knowledge extant in the engineer corps before 1796 or from some particular and as yet unascertained progenitor. Whatever the origin of these early towers, it seems fairly certain that the knowledge passed to Halifax in well-developed form under the aegis of Captain Straton, Edward's Commanding Royal Engineer. Edward credited Straton with the proposal for the Prince of Wales Tower on Point Pleasant and the short interval between its suggestion and commencement, a mere two months, suggests that little local initiative was required in its planning.⁹

Any cursory examination of the source materials relating to the origins of Martello towers generally, or the early Halifax towers in particular, is not very enlightening for, as one student of the subject notes

Towers, armed with cannon at top, have always been considered a good expedient for the defence of a coast, and have been built of various shapes and sizes, in different countries and situations.¹⁰

Nonetheless, a perusal of such material as is available is made worthwhile by the information it provides on the development of the prototype English towers.

S.G.P. Ward. in his careful study of this developmental process, Defence Works in Britain 1803-1805, clearly attaches great importance to the Minorcan towers which in turn, as has been illustrated, must have been influenced by the presence of the older patterns of Mediterranean towers. Captain D'Arcy, the engineer officer in Minorca while the British held the island in the years 1798-1801, superintended the construction of 15 cannon-armed stone towers during that period. D'Arcy himself was a firm believer in towers as detached works and his efforts could hardly have failed to make an impression on his professional peers. The largest of these Minorcan towers

were 55 feet in exterior diameter at top, their exterior height being 36 feet with a slope of 1-12th. The thickness of the parapet was 12 feet all round; its height 6 feet; and its dip 2 feet 6 inches. The height of the lower storey of the towers was 11 feet; over which was a wooden floor covered with paving tiles . . . the height of the upper storey measuring to the crown of the arch was 15 feet 6 inches. The bombproof arch was a dome of a section nearly elliptical, the span of which was 31 feet, and its rise 11 feet 8 inches. The dome and exterior outline of the tower were described from the same common center. The thickness of masonry over the crown of the dome was 5 feet.

Above the principal entrance, which . . . was a door placed on the level of the upper apartment, there was a machicooly [machicoulis]. . . . The ascent to the terrace was by a spiral or winding staircase, set in the wall. A hatchway and ladder led to the lower storey, which was partitioned off into three apartments. There was a cistern excavated below the general level.

A long heavy gun, whose centre of motion was in the rear, was mounted on these towers; but as there was more than sufficient room for one gun, a howitzer or carronade was also added.¹¹

The likenesses between these towers and the English Martello towers are startling; in essence the Minorcan towers lack only the central pillar to assist in sustaining the bombproof arch.

There is, however, no evidence to connect either Captain D'Arcy or any of the other Minorcan engineers with the earliest English tower proposal. This was drawn up by Captain W. H. Ford, R. E., and submitted in an undated memorandum through the intermediary of his superior, Colonel William Twiss, R. E., sometime before July 1803. Ford described a two-storey square tower mounting a heavy traversing gun on top. Ford also appears to have made drawings of round towers similar to that on Minorca. Ford joined Abercromby's army in October 1800, serving in Egypt until February 1802. Ward surmises that he was in Minorca where Abercromby's force was assembled in the autumn of 1800 and so would have observed the towers there.¹² Despite his careful development of circumstantial evidence on behalf of Captain Ford, Ward himself balks at definitely ascribing the plan of the English Martello tower to Ford through the medium of the Minorcan tower. He is forced to conclude rather lamely that

In viewing the modifications both in design and intended employment through which the Martello Tower passes, we are left only with the conclusions, even taking Ford's contribution and the Minorquin towers into account, that it cannot be said to have had a single "inventor" . . . that though it bore the name of the Corsican tower, the transplanting process to England is invisible: that an immediate connection between it and the towers in Minorca can, on the other hand be established: and that, in any case, towers mounting ordnance were more deeply bedded in Engineer tradition than might have been expected.¹³

The arrival of the idea in England had an immediate and controversial impact on defence planning. The war with revolutionary France had produced a number of invasion alarms in England. There had been one in 1797-98 and another in 1801, when a vast French force massed at the invasion port of Boulogne. Defensive measures had been under way since 1796 and the Peace of Amiens in 1801 provided a brief respite, but no relief, from the threat. When the war was renewed with imperial France on 24 May 1803, the French forces massed on the Channel were even larger than before. All manner of defensive schemes were brought forward by the various military agencies in the prevailing atmosphere of crisis. Lacking the resources to defend the whole coastline, the military authorities quickly narrowed the likely invasion points down to areas of the south and east coasts. Of these the most severely threatened were those on the Sussex and particularly the Kent coasts.

It was at this critical juncture in the summer of 1803, with the Horse Guards already contemplating massive expenditures along the south coast, that Captain Ford came forth with his tower proposal. He suggested that each of his towers could be erected at a cost of £3,000, would be long enduring, and would require no regular garrison, and, if peace came, their ordnance could be dismounted and the towers shut up to await a renewal of conflict.¹⁴ Ford apparently intended that his towers should be placed at short intervals along the threatened coast and be mutually supporting. Ford's idea was taken up by his superior Colonel William Twiss, the Commanding Royal Engineer in the southern district, an acknowledged defensive expert who had served in British America as an engineer with Carleton, Burgoyne and Haldimand. Twiss did not favour scattering towers along the whole coast, preferring instead to erect them as adjuncts to existing coast batteries, and his endorsement of Ford's scheme on 22 July 1803 was couched in these terms. A year earlier he himself had endorsed a proposal for a round tower for a redoubt in Ireland.¹⁵

Twiss's and Ford's 1803 proposal was passed quickly up the army chain of command where it found enthusiastic or conditional support at every turn. The Horse Guards considered fortifications the only sure means of defence¹⁶ and quickly adopted Ford's proposal in its entirety. The Quartermaster General's department had no funds to initiate it, however, and the Secretary of State for War referred the scheme to the Master General of the Ordnance for engineer opinion and approval, as its implementation would be an engineer responsibility. The towers had already received the approval of the commander-in-chief, the Duke of York, who accepted them as a means of extending the existing coast defences because of their cheapness, the impossibility of taking them except after heavy artillery fire, and their capacity for protecting a coast as well as a body of troops could do.¹⁷

The engineers, however, overwhelmed with work and short of qualified officers, displayed little enthusiasm for the massive building programme and the report of the committee of engineers was not returned until 26 April 1804. This report was signed by Lieutenant General Robert Morse, Inspector General of Fortifications, General Abraham D'Aubant, a prominent engineer officer who had inspected the Guernsey towers in 1787 and witnessed the assault on the Corsican tower in 1794 as second in command of the expedition, and Colonel Twiss.¹⁸ This committee reported sceptically on the proposed building programme:

Towers as sea-batteries . . . appear to have little or no advantage over any other battery of the same number of guns. It is admitted that upon first landing of an enemy a tower is not to be taken by assault; but a few shells thrown by small mortars brought on shore . . . might in a short time destroy the carriages of the guns on the platform or top of the tower and thereby render its effect as a sea-battery useless. Therefore after a full investigation of this subject, we do not recommend the erection of towers as sea batteries or to obstruct the landing of an enemy.

They did, however, recommend circular towers to supplement existing or proposed batteries, and selected 13 sites for these at an estimated cost of £57,000.¹⁹

This critical assessment was sustained some years later by Lieutenant Colonel Pasley in his textbook on elementary fortification. Referring to the successful engagement of the Corsican tower with two ships of war, he said.

This circumstance ought merely to have proved the superiority, which guns on shore, must always in certain situations, possess over those of shipping, no matter whether the former are mounted on a tower or not . . . . [In the same war] a common two-gun barbet battery, situated on a commanding cliff on the coast of the Kingdom of Naples, beat off a British 74 gun ship, supported by a frigate . . . a party of seamen and marines were landed with a couple of field pieces, who in a very short time made themselves masters . . . of this insignificant work . . . . The Corsican tower, above mentioned, which had in like manner completely baffled a naval cannonade, was very soon found to surrender, when attacked by land; not, however, before a small battery had been made to reduce it.²⁰

The critical engineer committee report of 1804 should have weighed heavily against the general and extended use of towers as sea batteries but did not. It did not because political pressure was mounting in every quarter for their construction. The Admiralty and the Duke of York favoured towers, and even Pitt, the Prime Minister, was displaying a personal interest in their completion. They had been urged in a House of Commons speech at the end of 1803 and, under the continuing threat of invasion, Twiss, on 12 September 1804, after consultation with the Prime Minister and the Deputy Quartermaster General, recommended the construction of 88 round towers on the south coast at a cost of £221,000. This decision was confirmed at a high-level conference on coastal defence on 21 October, and the final number of towers was set at 86. In the event, 74 of them were constructed between Folkestone and Seaford.²¹ Although Ford's original design had been for a square tower, the circular pattern had been settled on by the engineers earlier in October 1804 for reasons of economy, and was confirmed at the conference on 21 October. Definite orders to commence construction were finally issued on 27 December of that year.

The long and involved controversy surrounding the choice of pattern and decision to construct the English Martello towers is worthy of note chiefly because it is so illustrative of the preponderance of political over military considerations whenever or wherever the question of constructing Martello towers arose. As no Martello tower was ever subjected to attack, any view of their military virtues must remain conjectural, but an analysis of the English controversy, viewed in the light of what later occurred in British North America, must lead one to the inevitable conclusion that this consideration was, for the most part, of quite small consequence. Clearly the engineer corps favoured restricting the use of such towers to positions where they could serve as battery keeps and be afforded some supplementary protection by the main works. On the other hand, the politicians appear to have pressed for their extended construction, under pressure of an attack of "war nerves," because they could he readily and quickly built, made small demands on valuable men and equipment, and because they created the appearance of extensive preparation at minimal expense to the Treasury. These same considerations were to operate later in the construction of the towers at Kingston, Quebec, and other parts of British North America.

The main group of towers on the south coast was not completed until 1808, but once initiated, a craze for coastal tower building swept over the British Isles. Fourteen were built in Ireland in the Dublin area before the end of 1805 and others added later, and three completed in Guernsey at the same time. Twenty-nine towers were constructed on the east coast between 1805 and 1812, and in Jersey a line of towers was erected on the shoreline.²²

The main group of English towers on the south coast was later acknowledged by the board of ordnance to have cost a total of £223,000, or an average figure very near Ford's first estimate of £3,000 each. All of the British towers were completed in the short space of years before the end of the Napoleonic Wars and the government was not, after 1815, tempted to further construction of them for military purposes at home. In fact their military value was soon cast into some doubt and the first of the towers was disposed of by the Ordnance as early as 1819. Most, however, survived and 27 of those on the south coast remain today.²³ Some of the latter were pressed into service in World War II, as were a number of their Canadian counterparts, being among the most durable of all the 19th century fortifications.

None of the British towers was ever regularly garrisoned, although most were armed and maintained in service until rendered demonstrably obsolete by the introduction of steam war vessels and the great upheavals that characterized armament and coast defence technology in the 1850s and 1860s. From the outset the towers had many critics although they continued to find advocates for years. Among the critics was George Murray, who had participated in their construction and who later, as Master General of the Ordnance had expressed serious doubts as to the worth of their repair. It should be noted, however, that as Murray was questioning the virtue of the towers at home he was acquiescing to the Colonial Secretary's desire for the construction of their counterparts at Kingston, Canada.²⁴

In 1844, Colonel Lewis, R. E., a noted chronicler of fortification technology, noted the whim and accident that had determined the use of towers along the English and Irish coasts, but nonetheless suggested the utility of such towers in forming keeps for batteries. He included in his article a number of drawings of types of towers variously used in the British service, and among these were drawings for a three-gun tower which he felt to be best adapted in terms of size and cost to the purposes of sea defence. This tower, ovoid in plan, is obviously derived from the original Martello tower and must have been of an officially accepted pattern, as it is identical with those proposed for Kingston in 1841.²⁵

One of the last advocates of the English towers was the Duke of Wellington, who, when consulted about them when a new invasion threatened in 1845, replied,

My own opinion is in their favour. At all events, if they are nothing else, each of them is an excellent defensive guard house, which can not be surprised and may be defended for ever against anything but a regular attack by a superior force.²⁶

Wellington himself nonetheless recognized the efficacy of steam war vessels against such structures and, although the towers are implicitly dismissed rather than frankly condemned in later general assessments of the coast defences, the towers military usefulness could not have long outlived Wellington's qualified approval of them. Indeed the obsolescence of these towers was so generally recognized by 1860 and they were so superfluous that in August of that year one of them, No. 71 on the Sussex coast, was used as a target and utterly destroyed in a firing trial of the new rifled Armstrong guns.²⁷ To a large extent the latter-day history of the British towers parallels the North American experience, although in British North America their obsolescence was more slowly recognized, and, due to the general paucity of funds for erecting a modern and extended system of colonial defence, greater efforts were made to adapt the existing structures to the changing conditions of warfare imposed by steam navigation, a multiplicity of heavy smoothbore ordnance and later the rifled gun.

The prototype Martello towers, approved for the south coast at the end of 1804, which directly or indirectly determined the style of all but three of the British North American towers, were intended to be of the same pattern but in two different sizes. The larger, of which only two were built, were to mount 11 guns; and the smaller were to be armed with a gun and two carronades on top. Unlike their Canadian counterparts the English towers were not intended to be armed on their barrack floors. This is perhaps indicative of the concept of the home government that they were almost exclusively elevated sea batteries, difficult to escalade but little able to resist a land assault assisted by artillery, and so not requiring an extended flank defence. In British North America, however, their low cost and military popularity recommended their adaptation to a variety of circumstances in which such a carronade defence was essential. A standard feature of the English towers not generally found among those in Canada was a system of counterarches beneath the lower floor to increase the stability of the foundation. This was probably necessary because most of the English towers were located on beaches near the water where no firm footing was available. The only Canadian tower in a like situation, Sherbrooke Tower, built on a sandy spit in Halifax harbour, was similarly structured.²⁸

The English south-coast towers were circular in plan, although they appeared oviform, as the external and internal circles were struck eccentrically to make the wall thicker on the seaward than the landward side. The later east-coast towers were to be 26 ft. in internal diameter, 33 ft. in height from foundation to parapet, with walls tapering from 9 ft. 6 in. in thickness. All of these towers were built of brick. whereas in North America the preferred materials were either rubble or ashlar masonry, or a combination of the two. The English towers were two storeys high with the upper storey, covered by a bombproof arch, serving as accommodation for the troops. The lower floors of some were also arched and were usually divided by brick partitions into three or four compartments, one of which served as a powder magazine, the other being used for provisions and stores. A small cistern was usually built below this lower floor. Above the bombproof arch, each tower had a flat terrace or terreplein of solid masonry secured by a parapet and banquette all round. In these English towers the depth of masonry over the crown of the arch was rarely less than 5 ft. The usual height of the parapet was 6 ft. and the banquette was 1 ft. 6 in. wide. Entrance to the towers was by a door at or slightly above the level of the upper storey, reached by a ladder, movable stairs, or a drawbridge. The lower storey was reached by a hatchway and ladder or stairs through the barrack floor, while access to the terreplein was provided by a shaft cut through the arch or by a staircase cut in the exterior wall of the tower. The upper floor of the tower was always substantially loopholed while the lower storey was ventilated only by baffled air-holes that denied an attacker any access to the tower on that level. The upper storey contained a fireplace for cooking and heating set in the exterior wall with a chimney through the wall to the top. The doors of the towers were always placed on the land side, it being the least likely to be subjected to cannonade.²⁹

All English towers had domed, annular or simple arches. The most frequently found form, however, and the one incorporated in all of the south-coast towers as well as most of those built later in Canada, was the annular arch, which springs

from two concentric circular piers, one of which is formed by the exterior walls of the tower, whilst the other consists of a small round pillar, built in the middle of it. In any section taken through the center of a tower, constructed in this last manner, two arches will appear, but in reality they are to be considered as only one continued arch, the plan of which is circular, so that it encloses a space like a ring.³⁰

The interior faces of the parapet of English east-coast Martello towers were indented, or shaped in semi-circles to conform to the demands of the traversing platforms on which their ordnance was mounted. Such terreplein ordnance required a platform diameter of 16 to 20 ft. depending on the calibre of gun, and the parapet was shaped to those dimensions.³¹ The shaping was to permit the muzzle of the piece to project beyond the interior slope of the parapet at the time of firing to avoid muzzle blast effects on tower and gunners. A variation of this form of construction and gun mounting was incorporated in most of the towers built in the Canadas, though it was not copied in the Maritimes.

Despite the numerous British American technical adaptions of, and in some cases improvements on, the structural pattern of the English towers, the most salient distinction to be drawn between the two groups of towers is the often widely differing conditions of their use. Almost all of the British towers were erected on the open coastline or on the shoreline of harbours to resist a sudden assault from war vessels at sea. Restraints on their use as land defence works amounted to a generally accepted prohibition, as Pasley remarked in 1822:

It ought to be clearly understood, that the chief advantage of Martello Towers is their non-liability to be instantaneously entered and taken possession of, by sudden assault, after the landing of an enemy: because as far as regards the mere effect of the guns mounted upon them, if engaged by shipping in a distant cannonade, there can be no doubt, but that the same number of guns would be equally efficacious, if placed in a common low field battery. The round figure of the Martello Tower is some advantage, because when exposed to a cannonade, all the shot, which strike it obliquely, glance off, without materially injuring the masonry.

This advantage, however, is of importance only against ships, whose fire is uncertain. In opposing a land battery, constructed within a moderate distance, and firing with the usual precision, it would be of little avail, because almost every shot might be made to strike perpendicularly upon the centre of the building. Martello Towers therefore are not to be recommended in inland fortresses or positions; although no other kind of works are, upon the whole, better adapted for the defence of an open beach against a hostile fleet.³²

A few of the British towers were provided with dry ditches and bombproof masonry counterscarps and glacis but most were erected on beaches so close to the edge of the sea as to preclude such an expedient.³³ A few of the towers were in fact destroyed by erosion and heavy seas.³⁴ This limited use produced a curious blindness in Britain to the value of Martello towers as redoubted battery keeps, or to their isolated landward deployment behind similar cover in the smooth bore era, with the single exception of Twiss's unimplemented proposal of 1806.

In British North America, where different conditions of warfare were deemed to prevail, and where the engineer and other officers on colonial service were generally forced to seek inexpensive means of defending their batteries and other works against assault from any quarter, the above strictures on the use of Martello towers did not usually apply. Although there are several classic cases of the water-level location of Canadian towers, and other examples of their construction in situations that permitted only a single likely avenue of approach, these towers, both those projected and those actually constructed, were freely adapted to a wide variety of locally pertinent circumstances, including their use as battery keeps — revetted and unrevetted — in both land- and water-bound locales, and their employment as independent outworks inland. While the lack of wisdom of some of these choices was later recognized and measures planned or undertaken to increase their security from artillery fire, it is a fact that in British North America, Martello towers were employed with much greater versatility than they were in Great Britain.

It is this variety of adaptive employment over a wide geographical area, in numerous peculiar local circumstances and across the changing demands of a half century of British North American defence, that makes a detailed study of the construction, alteration and final disposition of the Canadian Martello towers a particularly valuable and instructive exercise. Though the first three British North American towers did not share the same technical progenitors as their later fellows, all, like their English counterparts, were aspects of an emergent British fortification technology initiated by an accident on the coast of Corsica in 1794 and definitively terminated with the widespread introduction of the rifled gun after 1860.