|IX.–Notes on the Island of Ascension.||By Captain H. R. BRANDRETH, R.E.|
IN the year 1829 I received instructions from the Admiralty to proceed to the Island of Ascension, to make a report and survey of the island previous to the adoption of certain measures recommended by the Commandant, Captain Bate, of the Royal Marines, which would have the effect (if sanctioned) of confirming the final establishment of the island as a permanent station ; and my attention was principally directed to three points : 1st. The defence of the island, and the necessary means of accommodation for the troops. 2nd. The means of procuring water, and of conducting the supplies from the mountain district to the town. 3rd. The state of cultivation, and the encouragement necessary to raise stock and vegetables for His Majesty's ships of war, and merchant ships of any nation, touching at the island.
I was also directed to report generally on the condition of the island in reference to its existing and probable future means as a colony.
Ascension is situated in 7° 55’ 56” south latitude, and 14° 23’ 50” west longitude. It is about eight miles in length, and six in breadth, and lies within the immediate influence of the south-east trade wind. The whole character of the island is volcanic, and its surface is broken into mountains, hills, and ravines. The mountain district extends principally over the south-east portion of the island ; and the “Peak,” or greatest elevation, is 2870 feet above the level of the sea. The plains or table-land surrounding the “Peak” vary in height from 1200 to 2000 feet. On the north side they sweep gradually down towards the shore, but on the south they terminate in high and bold precipices. Steep and rugged ravines intersect these plains, which, commencing from the highest lands, open into small bays and coves on the shore, fenced on each side with masses of compact and cellular lava. The sides of these ravines disclose extensive beds of cinders and ashes. Volcanic tufa occurs in the form of rocks, but is in general distinctly stratified. Red iron clay, tufa, blue clay (resembling marl), and decomposed trachyte, alternate with the strata of cinders and ashes, and, wherever recent sections occur, present the most distinct arrangement. Pumice is found on the plains and corresponding parts of the mountain district, and. occasionally on the shore. It is found in detached pieces, or mixed up with cinders and clay, and occasionally with a conglomerate of red iron clay, cinders, ashes, scorić, and nodules of lava. Trachyte rock appears to extend all round and throughout the mountain district ; in several parts resembling the arrangement of basaltic columns, and in others chalk cliffs. Masses of this rock disclose themselves near the mountain ridge, and it passes from the compactness and hardness of sandstone to entire decomposition.
The hills dispersed over the island vary in height from 1000 to 1500 feet above the sea, and offer, with few exceptions, no evidence whatever of having undergone any change since their volcanic origin. They abound with cinders, scorić, and ashes, and are surrounded at their bases with compact and cellular lava, and occasionally with obsidian. They in general possess vestiges of an original conical form, having the surface smooth and regular towards the north; but an the south they are broken, hollow, and precipitous, with here and there the appearance of a lateral discharge of lava, which may be traced in its course towards the shore.
Plains of cinders, ashes, and scoriae, and finely pulverized earth, spread over that portion of the island which lies to the north-west of the mountain district, intersected with water-courses of fine gravel, and pebbles of lava and silex. Masses of lava and scoriae also occur on these plains, 20 or 30 feet high, heaped together as if by art, and for the purpose of clearing the land.
Extensive beds of lava and scorić surround the island, indenting the line of coast with small bays, coves, and inlets.
From north-east bay, south, to south-west bay, the coast is singularly bold and precipitous. On the opposite coast the beds of lava spread out into the sea, and assume a variety of forms, columnar, arched, or cavernous ; and their surfaces are remarkably rugged, splintery, and difficult, and even dangerous far the stranger to traverse. These formations are locally termed “climpers.” Stalactites of sulphate of lime are found in the coves on the shore.
Limestone occurs in great abundance in some of the bays and coves, It is a beautiful specimen of calcareous tufa, consisting of small particles of shell, rounded by attrition, and united by heat and pressure. Excellent lime is obtained from it, which, when mixed with three, and even four, parts of the volcanic earth, forms good mortar.
The dark and rugged beds of lava, the deep red colour of the hills, the wild and capricious forms of the mountains and precipices, and the prevailing apparent recent indications of volcanic action, impart to the aspect of the island a character of total sterility and desolation that does not really belong to it. It is important to notice this, as the impression made on the transient visitor is perhaps to the last degree unfavourable ; while a detailed examination of the features of the island is calculated in some degree to remove this impression.
The population, at the period of my arrival, consisted of about 140 Europeans, principally of the Royal Marine corps, and 76 Africans ; making a total of about 220 persons, including military and civil officers, and a few white women, (the wives of the non-commissioned officers and privates of the Royal Marines), and black women and children.
Ascension was first occupied as a post by Admiral Sir George Cockburn on the arrival of Napoleon Buonaparte at St. Helena, to aid in the surveillance of that island ; and was placed on the establishment of a sloop of war. A small town, or rather village, thus grew up near the roadstead ; which on my arrival consisted of a collection of miserable tenements, with walls put together without lime, and harbouring vermin ; roofs of canvass or shingles, and floors of sandstone or tarras. The hospital, which occasionally received the sick of the African squadron, was placed in a hollow, and consisted of four rooms, each about 16 feet by 11 ; and the Africans occupied wretched hovels, dark and filthy. A victualling store, a tank, and a small stone tenement for the officers, were the only buildings that redeemed the establishment from the appearance of an African village. In the country, a mountain district, the accommodations were somewhat better for the officers ; but the establishment generally was similar to that of the town.
The principal position, called George Town, already alluded to, lies on the north-west coast. It has an open roadstead, with good anchorage, about three quarters of a mile from the shore, in twenty fathoms water. The anchorage was defended by a few guns, on a projecting slip of land, about 70 feet above the sea, but without any breast-work or other cover; and in the rear, on a higher elevation, a building with a canvass roof was occupied as a powder magazine. Nearly parallel to this position was a second slip of land, of lower elevation, which had been formed into a pier or landing place, protected at the head with masonry, and with a flight of steps to the water.
The main. road of the island communicated between George Town and the mountain establishment near the “Peak.” The road was traced over the cinder plains, and round the base of the hills, and ascended over a steep spur of the mountain by several zigzags. The road was well traced, and extremely creditable to so young an establishment. It was probably easily worked out of the cinders and ashes, but from the same cause easily liable to decay.
Other roads, or rather tracks, had been worked in the lava district, and around the mountain lands ; but the greater number were imperfectly executed, were traversed with difficulty, and scarcely one of them admitted the passage of a carriage of any description.
The supply of water at this time was scanty and precarious. It depended on springs, or rather drips in the precipitous banks, and the rains that could be collected in casks and a few old iron tanks. A stone tank at George Town, calculated to hold about eighty tons, was supplied with water from the mountains, a distance of six miles. Three carts, six oxen, and three drivers, were employed daily in the transport of about three hundred and sixty gallons of this water. The supply from the whole of the drips was estimated at about four hundred and eighty gallons per day ; but even this quantity was liable to considerable diminution after long droughts. It does not appear that there had been at any one time one hundred tons of fresh eater in store on the island.
Several attempts had been made to procure a further supply of water by boring. The auger had been. introduced nearly horizontally, or in the direction of the substratum ; along which it was supposed the water passed, and formed a drip on the face of the precipice. The object, I presume, was to cause the stream to flow more freely ; certainly not to arrive at the source of the spring. But besides this, the Commandant, acting on the advice of an eminent naturalist who had visited the island, sought for water by the usual process of boring. The spot selected was near high-water mark, on account of the neighbourhood of calcareous tufa, in the formation of which fresh water was considered an indispensable agent. The experiments were attended with great labour, and were unsuccessful. Those concerned in them were probably not aware that, according to experiments, the vapour from salt water, intensely heated under pressure, will, by passing through loose sand, agglutinate the particles and form the solid sandstone of Ascension without the agency of fresh water : consequently, that this would not necessarily be found in its neighbourhood. A second trial for water in the low lands was decided on by the Commandant and myself ; and in the event of failure, I recommended other trials to be made in the mountain district.
In reference to agricultural productions, the island might at this time have been divided into four parts.
The first part consisted of about two hundred acres, situated in and about the highest land. In most mountainous countries cultivation commences from the shore and ascends to a certain height, beyond which it is unprofitable; and nature is usually left unmolested and untamed. In Ascension precisely the reverse occurs : decomposition commences from the apex of the mountain, spreads down its sides, and is limited at certain stages, where the state of the atmosphere ceases to aid in altering the original volcanic condition of the soil. The first or highest portion of the land therefore is the richest, the vegetable soil being here occasionally from 2 to 3 feet deep ; and in the ravines and hollows an alluvial deposit of greater depth is found, the substrata being cinders, ashes, and clay.
About forty-five acres of this, then, were in cultivation at the time alluded to, producing the sweet and English potato, peppers, tomatas, cassava, calaloo (or West Indian spinach), carrots, turnips, cabbages, pompions, French beans, and a few pines, bananas, and water melons. The Cape gooseberry (physalis edulis), a very grateful fruit for a tropical climate, was also found wild over this district. The sweet potatoes were as good in quality as any I had seen in the West Indies. The English potato did not thrive equally well, as is usually the case within the tropics.
Of the several wild plants that I found, scarcely any were useful ; they were for the most part tropical, and of the worst kind, being important only as forming a basis by their decay for the improvement of the soil.
On my return I submitted these plants, and portions of the soil in which they grew, together with sections of the ground, and the meteorological observations I had made with Daniel's hygrometer, to the Secretary of the Horticultural Society, who expressed an opinion that the soil and climate of the mountain district were favourable to cultivation.
The second division of the island consisted of about seven or eight hundred acres, lying around the “High Peak,” from about 1400 to 2000 feet above the sea. The soil here varied in depth from 6 to 18 inches, lying on beds of cinders, ashes, scorić, and trachyte. The cattle and other stock grazed over this portion, and part had been planted in turnips. The temperature was steadier than that of the higher land, but less moist.
The third part or division of the island included those tracts of cinders and ashes that lie about all the lower lands. The only change that takes place in these hot and arid regions is after heavy rains : the thirsty soil rapidly absorbs the moisture ; and the purslain springs up, and singularly contrasts its bright green and succulent leaf with the parched and waste surface. The only other evidences of vegetation are patches of hard wiry grasses. If, however, this district were visited with a degree of moisture like that in the mountain. lands, the soil would decompose, and be rendered capable of cultivation.
The fourth and last division of the island consists of extensive beds of lava, that will not undergo any change for an indefinitely long period.
From the examination of the records of the seasons, the concurring testimony of all residents, and my own observations, I consider the climate of Ascension to be decidedly, and in reference to its proximity to the equator, peculiarly healthy.
The difference between the heat and moisture of the mountain establishment and George Town is considerable.
In the former, the thermometer ranges, during the year, from 62° to 80°, and averages 70° ; in the low lands the thermometer ranges from 70° to 88°, and averages 83°.
Daniel's hygrometer gave a difference of 10° in the mountain moisture over that of the coast, and the proportion of rainy days is as 3 to 1 nearly.
The temperature of the mountain district would appear better adapted to Europeans than that of the coast. But, from its elevation, it is very frequently enveloped in cloud and mist, and subject to greater changes than the coast. The latter is not only peculiarly healthy, but has the advantage of a drier and more equable temperature. It is perfectly free from marsh miasma, and from any of the usual sources of malaria in tropical climates.
According to the Medical Report, the complaints among the troops are: Remittent fevers–Dysentery–Hepatitis–Diarrhoea, and occasionally, Pneumonia–Rheumatism, and catarrhal affections. The former are peculiar to all tropical climates, but in this instance they occur under a mild type, and give way to the usual remedies.
The hot months of 1818 are recorded as having been sickly, owing, it is stated, to an unusually wet season.
In 1823, and at a much later period, some severe sickness prevailed in the island ; the causes are not very distinctly proved, and I am greatly of opinion that they may be traced to imported disease from the African coast.
Convalescents from the African coast rapidly recover in the island.
The fact that the white men can work without injury seven or eight hours per diem throughout the year is important ; and I observed that the general appearance of the troops was healthy, and little characterized by the usual effects of tropical climates.
The year is divided into two seasons : the hot months commence in December, and end in May ; the cool season extends throughout the remaining months.
The rains prevail in the temperate season, but it does not appear that they are periodical in their recurrence.
The island is not known to have been visited by any severe tropical gales.
The “rollers,” or heavy swells, are the most formidable obstacles to which the shipping is exposed. I am not aware of their having occasioned any damage to vessels, but all intercourse with the shore during their action is difficult, and even dangerous. At Tristan d'Acuna the same phenomenon occurs ; and there, I believe, a vessel was on one occasion cast ashore by the violence of the rollers. I have never witnessed a similar action of the sea under precisely similar conditions elsewhere ; but it is probably not very uncommon. The rollers set in from leeward, rising suddenly from a perfectly smooth surface, moving in long vast ridges towards the shore, breaking over it with considerable violence, and abrading the line of coast. The most remarkable circumstance attending the phenomenon is, that the waves rise without any apparent or hitherto detected warning, and subside as suddenly, and entirely. A space of ten minutes only has elapsed from the first moment of their appearing, to that of their final and complete cessation. Various conjectures have been hazarded as to the causes. The rollers differ essentially in their motion from the long swell that precedes or succeeds a storm ; and from observations in the mountain, it would appear that they act only in the immediate neighbourhood of the island. It is possible that they may originate in volcanic action; occasioned by vapour generated below the bed of the water, and producing a sudden impulsive force upwards.
Having submitted to the Admiralty a Report on the island, with certain propositions for the future improvement and establishment of this little colony, and the Lords Commissioners having approved of the same, I was directed fully to explain my views to the Commandant, and to mark out the principal works.
The objects of importance were:
1st. The occupation of certain points with sea-batteries for the defence of the coast.
2nd. Accommodations for officers and privates,–a hospital, storehouse, workshops, &c.
3rd. A line of iron pipes for conducting the water from the mountain to the town, tanks, &c.
4th. Certain measures for the cultivation of the ground, rearing stock, &c. I had previously consulted with the Commandant regarding these propositions, many of which, indeed, originated with him, and. were merely referred to me as professional points, and to arrange the necessary details. In all essential matters our views were in accordance.
I found, on my arrival, only one position occupied with guns ; it was the slip of land before alluded to, about 70 feet above the sea, and called Fort Cockburn.
On this small plane were mounted on wooden carriages without any parapet, or cover, or even platforms,
|Four||18-pounders||. . . . . Guns.|
|Two||12||. . . . . do.|
|One||32||. . . . . Carronade.|
|One||12||. . . . . do.|
The magazine, of loose stones and canvass roofing, stood in rear of these guns, and on a higher elevation.
The object in occupying this position was to defend the landing on each side of it ; and so far it was important : but in its then condition it was obvious the position was not tenable, and therefore the defences of the island might be considered wholly inefficient.
In proposing a plan of defence for the island, it was of primary importance to consider the probable personal means of the garrison.
To maintain a respectable position, and to defend the accessible parts of the coast, it would be necessary to have at least 400 men at command : 100 men would be dispersed among batteries between Pyramid Point and Nicholls' Bay (vide plan), for the defence of the coast, and the remaining 300 men would occupy an enclosed work near the sea, capable of communication with the shipping.
There were but two positions in the island that admitted of such a work being constructed ; the one at Pyramid Point, the other on Cross Hill.
Pyramid Point is about 2000 yards from Fort Cockburn ; the position is elevated from 60 to 80 feet above the level of the sea, and the approaches protected by extensive and rugged beds of lava. A small inlet, called Comfort Cove, affords facilities for landing, and might be defended by batteries on the two projecting points of the shore.
There would be ample space for an enclosed work about 300 yards from this Cove. The ground presents great difficulty to the approach of artillery, and there are no commanding elevations in the neighbourhood that would be occupied to advantage by an enemy.
The ground, however, consists of masses of splintery lava, scorić, and cinders, and could not be cleared without great labour. The principal objection, however, is its distance from the town or establishment.
Cross Hill is about 900 feet above the sea : the rise commences about 400 yards from Fort Cockburn, and its summit is about 1500 yards from it. The hill consists principally of cinders and light earth, so that a space on the top could be easily made for an enclosed work. The approach from the south is difficult, and ascent laborious on all sides.
The range from the summit of this position would be too great, and the fire too plunging, to afford an efficient defence for the proposed barrack establishment on the ground towards the interior. By throwing out batteries at lower elevations on the sides of the hill towards Fort Cockburn, a communication might be secured with the latter, and, consequently, with the shipping. There would, however, be a considerable difficulty in supplying it with a large store of water.
The line of coast from Pyramid Point to Nicholls' Point affords the principal facilities for landing. Both N. E. Bay and English Bay will also admit of landing ; but the steep and broken features of the country surrounding these latter Bays render the advance of an enemy extremely difficult.
Every other part of the coast is remarkably bold, and difficult of approach, and defended by beds of lava, or “climpers,” as they are locally termed.
The coast, therefore, from Pyramid Point to Nicholls' Point appeared to be the principal line to be defended ; and I proposed to occupy it in the following manner :
On this position I proposed the enclosed work described in the Plate, having five 24-pounders, and a defensible block-house for 35 men.
Battery No. l.–I proposed a tower with two 24-pounders mounted on the top, at Pyramid Point, to maintain a cross fire with Fort Cockburn, and to see into Comfort Cove. It is to be supplied with a tank and a magazine, and capable of an independent defence, accommodating 12 men.
Battery No. 2.–A small half-moon battery on Goat Hill with two 24-pounders, having a cross fire with Fort Cockburn.
Battery No. 3.–A tower of the same construction with Battery No. 1.
Battery No. 4.–A small enclosed work similar to Fort Cockburn, mounting five 24-pounders, with a block-house.
Battery No. 5.–A tower of the same construction as Batteries 1 and 3.
Batteries No. 3 and 5 are too elevated, being from 90 to 100 feet above the level of the sea ; but there is no other ground more favourable to admit of batteries forming a cross fire with Battery No. 4.
These works, with the exception of Battery No. 2, were proposed to be enclosed, and capable of an independent defence, should a landing be effected. Battery No. 2, from its neighbourhood to the establishment, did not require the same security.
The foregoing works would require the following personal means :
|Fort Cockburn||. . . . . 35 men.|
|Battery No.||1||. . . . . 12|
|2||. . . . . 12|
|3||. . . . . 12|
|4||. . . . . 25|
|5||. . . . . 12|
The principal object of these batteries was to defend the coast against such irregular attempts at landing as might be expected from one or two ships of war ; and through the signal-posts at Cross Hill and the mountain, the garrison would gain information of the probable point of landing.
I proposed a magazine for 500 barrels of gunpowder to be situated inland, and at a convenient distance, and where it would be secure from accident.
The principal portion of the materials for constructing these works are to be found in the island, and are easily procured and worked. They will be described hereafter.
I recommended that all the guns should be of one calibre, and mounted on traversing platforms.
In conducting these works I recommended that Fort Cockburn and Battery No. 4 should be first executed, as affording essential defence to the most important points of the coast.
In reference to what I considered might be the general strength of the garrison, not including provision for an enclosed work or citadel on Cross Hill, I proposed the following scale :
|130||Non-commissioned officers and privates ;|
of which numbers I recommended there should be 1 Subaltern and 25 Non-commissioned Officers and Gunners of the Royal Marine Artillery, to be in charge of the batteries and stores, and to instruct the garrison in the exercise of the guns.
The following memorandum on the guns and traversing platforms I had recommended, was furnished me by the late Colonel Sir Augustus Frazer, K.C.B., Royal Horse Artillery, to whom I was much indebted for his suggestions.
|“For Iron 24-pounder guns.|
|Gun Carriages||Weight 24cwt. 1qrs. 0lbs.||13cwt. 2qrs. 23lbs.|
|Price £13 9s. 5d.||£18 12s. 2d.|
|Traversing Platforms||Weight 45cwt. 3qrs. 0lbs.||18cwt. 3qrs. 19lbs.|
|Price £43 9s. 11d.||£31 18s. 2d.|
“These were prices when both iron and wood were dearer than at present ; so that 20 per cent. full may now be deducted from the price of iron carriages, and 12 per cent. from that of the wooden ones.
“The weight of the iron carriage and platform is obviously much greater than that of the wooden ones ; but the guns on the iron platforms are readily worked by the usual number of men, and no difficulty has been experienced on this account. The recoils of the gun had been moderate and easy, and no instance has occurred of the gun recoiling off the platform. On the supposition that this might be the case, the hind trucks were taken off the garrison-carriage, the gun recoiling on the hind axle-tree ; that is a convenient mode enough in the event of any of the trucks being disabled.
“All wooden garrison-carriages, made for wooden traversing platforms, will answer for iron traversing platforms. The guns can readily be elevated to 15° on the iron carriages and platforms, and the ranges may be taken as follows for 24-pounders :
|Ranges in yards with charges of|
|8 lbs.||6 lbs.||4 lbs.|
|P. B. . . . . 297||. . . . 248||. . . . 248|
|1° . . . . 720||. . . . 661||. . . . 581|
|3° . . . . 1240||. . . . 1213||. . . . 925|
|5° . . . . 1807||. . . . 1590||. . . . 1371|
|10° . . . . 2870||. . . . 2673||. . . . 2513|
|15° . . . . 3510||. . . . 3350|
At high elevations, easily obtained by taking off the fore trucks of the garrison carriage on which the gun is placed, and putting the first axle-tree on another garrison-carriage, 24-pounders will range as fellows at 36° :
|With charge of||3 lbs.||. . . . . 3900 yards|
|4||. . . . . 4150|
|6||. . . . . 4200|
|8||. . . . . 4400|
“These are all ranges without wads, which should never be used unless the guns are under depression, as they sensibly diminish the range.
“The small difference of range with high and low charges is, perhaps, worth attention at a station where the store of powder may be limited.
“There is no doubt that iron carriages and platforms will stand the shock of the firing of the guns placed upon them ; but it has been fully ascertained that they will break to pieces an being struck by shot. Nevertheless, in climates where wood is perishable, as well as for coast batteries generally, they are very valuable, from their obvious durability and economy.
|(Signed) AUGUSTUS FRAZER,|
|Colonel Royal Horse Artillery.”|
Ascension, like St. Helena, lying in the immediate track of ships on their passage home from the East, might, if occupied by an enemy, furnish the means of considerable annoyance to our commerce.
The peculiar qualities of the climate render it a desirable place of resort for the African squadron, and for the preservation of stores for that station.
It was also considered that measures might be adopted for supplying ships in general with water and fresh provisions.
For these purposes the garrison was composed of a detachment of the corps of Royal Marines and a few African labourers.
The duties of the garrison were far from being purely of a military nature. The officers and men were employed throughout the day in erecting buildings, forming roads, tanks, and aqueducts, in cultivating the mountain district, and attending the cattle and other stock. These were all considered as public duties ; and, in addition, the ordinary duties of the garrison were discharged.
The small community was, in fact, like the nucleus of a colony, but with the advantage of fulfilling all their various avocations in strict conjunction with each other, and under military discipline ; and therefore unity of purpose, a most important feature in a young colony, was thus secured.
Hence the buildings for an establishment of this description would in some respects differ from those that are ordinarily required for a garrison.
At the principal establishment, George Town, I proposed to erect a barrack for 100 men, on the principle adopted by Sir Charles Smith, R.E., for the West Indies, together with quarters for the officers, a hospital for 30 patients, and a storehouse.
The annexed drawings represent the fort and hospital that have been erected, and which are modifications of my original proposition.
Buildings on a similar construction were proposed for the mountain district, which have been erected, or are now in course of erection.
Smaller buildings, adapted to particular localities, and appropriated as detached dwellings, sheds, and other tenements for cultivation and. stock, were also projected for the mountain district.
The island abounds in materials for buildings of masonry.
Limestone is found in the bays and coves, from the landing place to South west Bay, which is easily quarried, and supplies both the material for mortar and building.
The limestone is the calcareous tufa, before alluded to, formed by the finely comminuted particles of shell on the shore, dipping into the sea at a very low angle, and lying apparently in regular strata : masses, of considerable superficial dimensions, are worked out, and applied for paving, coping, &c.
The particles of shells of which the stone is concreted, are used for sand with the lime made from the stone, and mixed with sea-water. After a narrow examination of several buildings constructed with this mortar, I was not able to detect any saline efflorescence or other indication of moisture. The circumstance is to be attributed to the extreme aridity and equable temperature of the low lands. As fresh water was scarce in the island during the progress of the buildings, I did not object to the continued use of salt water, with the following exceptions :
1st. In situations exposed to much moisture.
2nd. In tanks, or, at least, in that portion of the walls in immediate contact with the water.
3rd. In powder-magazines.
4th. In ovens and fire-places.
Besides the particles of shell used as sand for compounding with the lime, several other materials were found applicable to this purpose.
Volcanic ashes and tarras, or decomposed basalt, were much used ; and by adopting these materials in place of the sea sand, it was found that a much smaller proportion of lime was required, and consequently the expense of coal for burning lime was much reduced.
In addition to the calcareous tufa, there are three other kinds of stone more generally used for building.
1st. Trachyte, which abounds over the mountain district, and is easily worked out into blocks of any required size.
2nd. Compact lava, found in the low lands, and among the steep banks of the water-courses at the foot of the hills. This is the hardest and most durable material on the island, but is worked with so much difficulty as to be rarely used. It is employed, however, with greater advantage where large shapeless masses can he applied.
The third, and most general description of stone, is the common cellular lava, found in every part of the island ; it is easily worked, and appears durable. It is occasionally found to decompose, but the artificers select that which is best adapted to their purpose.
The water-courses supply sand for building near the mountain grounds : it is composed of fine gravel and minute pebbles of lava and silex, mixed with tarras.
The most important of the foregoing materials are procured with. ease in the neighbourhood of any projected works.
|H. R. BRANDRETH,|
|Captain Royal Engineers.|
Plan of the Island of Ascension.
Plate XI. Island of Ascension. Plans and Sections of Fort Cockburn.
Plate XII. Plan, Elevation, and Section of the Hospital at Ascension.
Notes about this version of Brandreth:
The text and plates were scanned from an original copy. OCR software was used to generate a text file which was carefully proof-read against the original.
Contributed by Barry Weaver.
Details of the original:
Brandreth, H.R. Notes on the Island of Ascension. Professional Papers of the Royal Engineers, Volume IV, pages 116-130 (text), 1840.
Plates: Three uncoloured plates:
Plan of the Island of Ascension.
J. R. Jobbins, Litho. Warwick Ct. Holborn.
Plate XI. Island of Ascension. Plans and Sections of Fort Cockburn.
John Weale, Architectural Library, 59, High Holborn. G. Gladwin sc.
Plate XII. Plan, Elevation, and Section of the Hospital at Ascension.
John Weale, Architectural Library, 59, High Holborn. S. Porter sc.
British Library shelfmark: P.P.4050.i.
Library of Congress call number: TA7.G7