235 



THE CIVIL EN'GINEER AND ARCHITECT'S JOLRNAL. 



[JlLY, 



MOTLEY'S PROPOSED BRIDGE OVER THE AVON. 



The above engraving exhibits a desi^jn for a bridge of 600 feet 

 span, wliich Mr. Motley nriiposes to construct over the river .Vvon, 

 iit St. Vincent's Iloclis, Clifton: he states that it can be built with- 

 out any cent rinjf. At a distance of 80 to 100 feet from the verge 

 of the rock he jiroposes to drive a number of iron piles, united 

 sulficiently strong to bear a strain of several thousand tons, to 

 which powerful tension-bars would be fastened, on tlie river end of 

 which cranes of sufficient st ength would be attached, and, by the 

 aid of a moveable platform, the first portion of the bridge would 

 be hung on the principle of a suspended bracket; this would con- 

 tinue to be enlarged in length and depth, and as the work would 

 commence on both sides simultaneously, the bridge would meet in 

 the centre, and its perfect rigidity be' effected. The cost of the 

 iron work of such a bridge, Mr. .Motley states, for a span of 600 

 feet, and to sustain a uniform load of 1000 tons, with perfect »a/ety, 

 would not exceed 30,000/. A model of the bridge may be sean at 

 the office of the Mining Juumal. in Fleet-street. 



LAIRDS GALVANISED IRON SECTIONAL BO.A.TS. 



Mr. Macgregor Laird has communicated to the JK'antical Maga- 

 zine the annexed illustration of iron-built galleys and boats he is 

 now constructing. Mr. Laird sti-.tes that this construction is a 

 simple contrivance to enable mercliant vessels to carry without 

 inconvenience, boats that, in case of need, would save the lives of 

 crew and passengers; — men-of-war, to carry double the number of 

 boats in the si)ace now occupied, discovery vessels to carry large 

 tenders;— travellers to carry boats in the space of a moderately sized 

 trunk ; — and merchants trading to the open ports of the Pacific and 

 Indian Oceans to send out lighters and small craft, at the usual 

 rate of freight. 



The sketches are the plans, elevations, and sections of two 

 descriptions of boat, built on the sectional principle. The larger 

 one (figs. 1 to 4) is a galley, 70 feet long and 12 feet beam, to be pi-o- 

 |ielled by negroes with paddles.* This boat is for the use of her 

 Majesty's Consul at Fernando Po, to enable him, without reference 

 to calms or baffling winds, to proceed when required to .my point 

 within his district, which embraces the Bights of Benin, Biufra and 

 Panasia, a line of coast of 1000 miles in extent, having the beauti- 

 ful island of Fernando Po in the centre. 



" To those of your readers who know Mr. Beecroft, and have 

 been upon the coast, I need not remark upon the advantages, the 

 facility of taking the boat to pieces, and reuniting her in a fe'v 

 hours without the assistance of mechanical or skilled labour, will 

 give that distinguished traveller in his future geographical dis- 

 coveries. And from my own experience I can truly say th::t if I 

 had again to ascend any African river, I would prefer three or four 

 of these galleys, each manned and propelled by fifty Kroomen, to 

 the best equipped steamers that ever left England. 



Ccmimercially, steamers can only pay in civilised countries. 

 Their excessive cost at first, and the constant outlay afterwards, 

 has ruined all African trading expeditions into the interior; while 



• The following letter is from Commander Bevis, R X., to Mr. Laird : — 



"Sir— With reference to your letter of the 8th uU., with its enclosure from Mr. Mac- 

 ppegor Laird, relativeto asecliona! boatbuitt of galvanised iron, said to be rcaiiy for survey 

 on the 16th ult. (but is not yet in a tlnislied state), and desirinet me to take to my assistance 

 some eompelent oiricer at Liverpool, who lias been on the coast of Africa to inspect this 

 boa*, and report upon lier efficiency, I beg to report for the' information of my Lords 

 Commission.'rB of the Admiralty, that I have on several occasions inspected tlie boat, and 

 once in tlie presence of Mr. Beecroft, the Consul at Fernando Po, there being no African 

 officer in this neighbourhood, and find her dimensions and efficiency as follows, viz.: — 



Length 6% feet 



Beam 12 " 



Deprh ami.isliips .. .. 4 " 



Depth forward and aft .. 6 *' 



Thicl^ness of plates 3-lC and J-incl»; displacement at 1 foot water line 7*05 tons; ditto 

 2 feet 20 80 tons. 



" Thrtre are eight sectional pieces, Wi". Iicnviest of which is 16 cwt., joined toseth^r by 

 angle-iron joints, lined Willi vnle:iiiised Indian rubber, the whole being secured togetlier 

 by screw-bolts and ntils, so tlial her own crew of forty or fifty men, can carry her over 

 any neck of land, and set her up ai^ain. 



*' Her light draft of water is estimated at 1 foot with her crew, with provisions, water, 

 &c., tor the same, at 2 feel. Slie is to puil Ihirty-elgiit oars, double-banfced, fitted with 

 three schooner sail*, jib and square-sail, having for nit;ht rrotection iron stanchions 

 covered with thin felt; she is aisj to be fitted wiUi air-tijhl galvanised tubes as a life- 

 boat. 



" From her lisht draft of water, and general lightness, she is particularly well adapted 

 to tatie the bars on the coast of Africa, where there is a short breaking s<'a, and/or j)ro- 

 i-feding u;) the riven, or to go in cftitse of alavcrs, as from her cotutruction she mast pull 

 aii'i sail very fLSt. 



"It is priip .»./a by Mr. Bwcroft, Oiat this boat should he fitted with a liiht brass Si- 

 poundor forwards; and with her crew trained to sm.ill arms, siie wouhi be tit to go in 

 chase of any slaxers in a calm, tiierefore submit that this class of boat, with increased or 

 diraiiiislied dimensions would be of !;reat service to the African squadron as tenders. 

 "I am, &:c., 



ifccrjwoJ, 'th March, 1850.. " THoMis BETI3, Commander." 



Builder's Measurement 

 Total weight of ironwork 

 Do. with woodwork, masts, 

 all complete 

 displacement at 1 foot water line T'05 tons 



sails, ^ 



i't tons 



