1850.1 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL 



105 



an infiitiatioi of water from the Thames. The practical conclusion to be 

 drawn from the observations, recoided in the author's several papers were: — 

 That tlie natural drainage and replenishment of the chalk stratum might be 

 traced and accounted for, by observing the alternation of level, in various 

 localities, and at different seasons. That any large quantity of water 

 abstracted from the chalk stratum, at any given point, caused a depression 

 of level around the point of such abstraction. That in the upper district 

 any such abstraction of water would interfere with, and diminish the sup- 

 ply of, the streams, by vthich the drainage of the district was regulated ; 

 and lastly, that the depression of level under London, by pumping from 

 Artesian wells, had proved that the rapidity of demand already exceeded 

 that of the supply ; and that any attempt to draw a large additional quan- 

 tity for public use, would be attended with disastrous consequences. 



It was suggested that, considering the great works of drainage and water 

 supply which were in contemplation for the metropolis, and {looking to the 

 essential importance of having accurate and authentic geological informa- 

 tion, in order that those great works might be executed on a sound and 

 certain basis, that the geological survey now being carried on by govern- 

 ment, in a remote district of North Wales, where no urgent need existed for 

 early geological information, and where no new works of paramount im- 

 portance were in progress, or in contemplation, should be transferred at 

 once to the metropolitan districts, with a view to throw light on the real 

 structure, mechanical and chemical, of the deep water-bearing strata, on 

 which opinions so varying and so conflicting had been advanced. 



An inquiry was made whether any steps had been taken by the council, in 

 consequence of the statement submitted at the meetingof January 29th, urging 

 the consideration of the manner in which the interests of the public at large, and 

 of the profession were likely to be affected by the attitude recently assumed by 

 the Railway Commission, in reference to the strength of the wrought-iron 

 bridges used on railways. — It was stated that the council had not as yet 

 taken any decided steps in the matter, hut that a course had been suggested 

 which, being followed, would most probably lead to satisfactory results. 

 After this assurance the members expressed their confidence of the interests 

 of the profession being in safe hands, and that every step would be taken for 

 insuring their position and professional reputation. 



The motion which had been prepared was therefore withdrawn ; and the 

 Chairman requested any communications on the subject to be made in 

 writing to the Secretary, who would lay them before the council. 



Feb. 12. — The first paper read was, "An Account of the Cast-Iron Light- 

 hotise Tower on Gibb's Hill, in the Bermudas.'" By Mr. P. Paterson. 



The site chosen for this tower was in latitude 32° 14' N., and longitude 

 64° 50' \V., being the southern part of the Bermudas, at which point they 

 are most safely approached. It was at first determined to construct the 

 tower with the materials found in the islands; but, after some progress had 

 been made in quarrying and dressing the stone, it was ascertained to be of 

 too friable a nature for the purpose, so that the Home Government instructed 

 Mr. Alexander Gordon, M. Inst. C. E., to prepare a design for a cast-iron 

 tower, similar to that which had been erected from his designs at Morant 

 Point, Jamaica, and which had proved very successful. The form of this 

 tower was that of a strong conoidal figure, 105 feet 9 inches in height, ter- 

 minated at the top by an inverted conoidal figure, 4 feet high, in lieu of a 

 capital; its extreme outside diameter was 24 feet, at the narrowest part 14 

 feet, and at the top 20 feet. The external shell was constructed of one hun- 

 dred and thirty-five concentric cast-iron plates, having inside flanges, and 

 varying in thickness from one inch at the base to about three quarters of an 

 inch at the top. In the centre of the tower there was a hollow cast-iron 

 column, eighteen inches in diameter in the inside, and of three-quarter inch 

 metal, for supporting Fresnel's dioptric apparatus, and in which the revolv- 

 ing weight descended ; it was also used, in the daytime, for raising and 

 lowering of stores, and likewise contained the waste water-pipe. The lower 

 part of the tower was filled with concrete, leaving a well, faced with brick- 

 work, about eight feet in diameter, and twenty feet in depth, in the centre. 

 Above this were the seven floors, the two lower ones being lined with 

 brickwork, and used as store rooms; and the upper ones, lined with sheet 

 iron, were used as living rooms for the light-keeper. The details were then 

 given of the mode of constructing the floors, the windows, the staircases, 

 and of attaching the lantern and light-room to the main structure; it was 

 Stated, that the light was visible from all points of the compass, excepting 

 ■when obscured by the high land between Gibb's Hill and Castle Harbour, 

 from the deck of a vessel at a distance of about twenty-seven miles, and 

 possibly at a still greater distance. The structure occupic-d less than one 

 year in its actual erection, the different parts having been landed about the 

 end of November, 1844, the first plate being erected on Gilih's Hill on the 

 19th of Decemlier, 1844, and the last plate of the tower on the 9th of Octo- 

 ber, 1845. The whole cost of the structure, including the lantern and light 

 apparatus, was stated to have been about 7,690/., and the annual expense 

 of maintaining it, about 450/. 



The next paper read was, "A Description of Sir George Cayley's Hot Air 

 Engine.'' By Mr. \V. W. Poingdestre. 



After entering briefly into the theoretical considerations of the expansion 

 of heated aeriform bodies, and detaUing the attempts made by Lieut. Ericc- 

 son, for employing hot air instead of steam, as a prime mover, the auliior 

 proceeded to state, that in 1837, Sir George Cayley, Bart., applied the pro- 



ducts of combustion from close furnaces, so that they should act at once 

 upon a piston in a cylinder, similar in every respect to that of a single-acting 

 steam-engine. The engine consisted of a generator of heat, a working 

 cylinder, and an air pump or blower, the air pump being half the size of the 

 cylinder, and blowing air into, and through, a fire perfectly inclosed within 

 the generator; the doors of the furnace were made perfectly air-tight as 

 soon as the fire vb.% well got up, the first impulse being given to the engine, 

 hy thowing a few jets of water upon the fire, which caused the air-pump to 

 w'ork immediately, and continued so for hours; the fire being replenished by 

 stopping off the blast from the furnace, and opening the upper bonnet. 

 After the air had passed through the fire, the gaseous products of combus- 

 tion, generally at a temperature of 600° Fahrenheit, passed laterally through 

 a chamber, used for separating them from any ashes or cinders, into the 

 working cylinder before alluded to. 



The ditHculties attending this description of engine, were the liability of 

 the working parts to be deranged, by the great sensible heat destroying the 

 valves, pistons, and cylinders, and carbonising the lubricating oil. It was 

 stated, that Mr. A. Gordon had made a successful experiment on the appli- 

 cation of the heated products of combustion for propelling a boat, without 

 the intervention of any machinery between the furnace and the water to be 

 acted upon. 



Feb. 19. — "Description of the Iron Roof over the Railway Station, Lime 

 Street, Liverpool." By Mr. Richard Turner. 



The area covered was described as being 374 feet in length, and 153 ft. 

 6 in. in breadth, which was roofed over in one span. The roof consisted of 

 a series of segmental girders or principals, fixed at intervals of 21 ft. 6 in. 

 from centre to centre; these were supported, on one side, upon the walls of 

 the offices, as far as they extended, and on the other upon cast-iron columns. 

 From the end of the offices to the Viaduct over Hotham-street, a distance of 

 60ft. 4 in., the principals were carried upon " box-beam" of wrought-iron. 

 The principals were trussed vertically, hy a series of radiating struts, which 

 were made to act upon them, hy straining the tie-rods and diagonal braces 

 they were trussed laterally hy purlins and by diagonal bracing, extending from 

 the' bottom of the radiating struts to the top of the corresponding strut in 

 the adjoining girder; these braces were connected with linking-plates by a 

 bar of the same scantling, and also with the purlins already referred to. 

 The girders were thus firmly knitted together, and a rigid framework 

 formed, upon which the covering of galvanised corrugated iron and glass 

 was laid. 



The whole construction was minutely described, and the appendix con- 

 tained an account of the experiments for testing the strength of the prin- 

 cipals. These were made at the works of Messrs. Turner and Son, Dublin, 

 under the direction of Mr. Locke, the engineer of the railway, when some 

 great improvements in the construction were introduced at his suggestion. 



SOCIETY OF ARTS, LONDON. 



Jan. 16.— William Tooke, Esq., F.R.S. V.P., in the Chair. 



Mr. AVALLsread a paper " On California, its History, Products, Climate, 

 and Prospects; being the result of a recent visit to thai place, by Alex- 

 ander Cross, Esq." 



On the table were placed a few specimens of Californian gold, one of 

 which was a large lump, weighing almost seven pounds, being the largest 

 ever imported into England in a pure native state, and the property of Blr. 

 Cross. A few specimens were also exhibited by Professor Tennant. Mr. 

 Walls commenced by stating the extent of the country and its population, 

 which, including the recent accessions, amounted at the present time to 

 90,000 people. 



The country along the sea-coast is healthy ; but fever is occasionally pre- 

 valent in the interior. After describing the situation of some of the prin- 

 cipal stations, he proceeded to describe the valley of San Joachim, its extent 

 and boundaries, every spot in which is stated to have produced gold of 

 twenty carats fine. Several extracts from various sources were briefly alluded 

 to in the paper; and from these the following matters were collected. 

 Two young men had discovered gold in a place 500 miles north of San 

 Joachim, and described their operations as having been attended with con- 

 siderable success, having made in their best day 400 dollars, in their worst 

 150 dollars. As to the moral coiidition of the people, many of them be- 

 came rich very quickly ; but some expended their gains in profligacy and 

 dissipation, so that the poorer class was fast increasing. The annual ex- 

 ports of gold from this country, according to Mr. Bryant's work on Cali- 

 fornia, amounted to between 100 and 2UO,UOO,000 dollars. In many places 

 linen washing was so expensive, that it was considered more economical to 

 thiow away old linen, and buy new. Emigrants, as they arrived, passed 

 beyond into the country, and were doing well. The general health of the 

 community was excellent. The disparity of the produce of laijour in va- 

 rious parts sometimes occasioned considerable confusion. A new settler in 

 about three weeks would succeed, by washing, to obtain an ounce of gold 

 a-day; but the moment that he hears that at a distant place others were 

 washing three, he immediately packs up his things, goes away, and is gene- 

 rally disappointed. 



