) 848.1 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL, 



13£ 



more modern ones its forms were repeated in the rock. After concluding 

 the Indian part of his subject, Mr. Fergusson pointed out the striking simi- 

 larity that existed between the arrangement of the buildings he had been 

 describing and those of Stonehenge, — which he had no doubt whatever was 

 a Buddhist building ; and he thought every part of that hitherto mysterious 

 erection admitted of easy explanation on that supposition. He concluded by 

 Ehowing how domes were constructed in India; and pointed out the simi- 

 larity that existed between the Indian examples and the well-known tomb 

 at Mylasae, in Asia Minor — and the curious circumstance that the hog-backed 

 Lycian tombs, discovered by Sir Charles Fellows, strongly resembled, not 

 only in form, but in construction, those Indian buildings which had formed 

 the subject of the lecture ; while the language of the inscriptions on them 

 was a dialect of the Sanscrit, about as far removed from the mother tongue 

 as that found on inscriptions in the Indian examples. 



March 20. — Mr. Eaton Hodgkinson was elected honorary member, and 

 Mr. Thomas Penson and Mr. Edmund Sharpe, M.A., fellows. 



The honorary secretary announced the following as the subjects proposed 

 for the medals : — 



" Her Majesty having been pleased to grant her gracious permission for 

 the Royal Medal to he conferred on such distinguished architect or man of 

 science, of any country, as may have designed or executed any building of 

 high merit, or produced a work tending to promote or facilitate the know- 

 ledge of architecture, or the various branches of sciences connected therewith, 

 the council will in January, 1849, proceed to award the Royal Gold Medal 

 to the author of some literary publication connected with architecture. 



" The Silver Medals of the Institute will he awarded — 

 " 1. To the best essay on the peculiar characteristics of the Palladian school 

 of architecture, and a comparison and contrast of its elementary principles 

 and details with those of ancient art. 



" 2. On the best manner of covering the roofs and forming the flats and 

 gutters of buildings ; the nature of the several materials used in various parts 

 of the country for these purposes ; their most efi^ectual and economical ap- 

 plication ; the inclination to be given to the diflFerent parts, and the other 

 practical precautions to be adopted to prevent snow and rain penetrating 

 into the building. 



" The Soane Medallion to the best design for a building to serve as a 

 national repository and museum for the illustration and exhibition of the 

 productions of the industrial arts. 



" The successful competitor for this medal, if he go abroad, will be entitled 

 to the sum of 501. at the end of one year's absence, on sending satisfactory 

 evidence of his progress and his studies." 



Amongst the books presented were an essay, on " Cyclopean Walls" 

 {Kyklopischen Mauern,) by Dr. Forchammer ; parts of M. Daly's " Rtvue 

 Generate de V Architecture," and of Mr. Fergusson's beautiful work on Indian 

 architecture. The foreign secretary, in commenting on the donations, 

 pointed attention to an article in the Rnue Gene'rale, complimentary to the 

 Institute for not restricting the competition for the Gold Medal' to this 

 kingdom. 



Allusion was made to the circumstance that all the impressions of Mr. 

 Leitch's translation of Miiller's " Ancient Art and its Remains" (of which a 

 copy was presented to the Institute at the last meeting), had been destroyed 

 by fire. 



Amongst the letters read, was one from Herr Lange, of Fiilda, acknow- 

 ledging the honour of his election, and setting forth several subjects on 

 which he could afford information, especially the Carlovingian monuments 

 (eighth and ninth century), of his neighbourhood, and a collection of terms 

 in use amongst the workmen of the middle ages. 



Mr. T. H. Wyatt read a paper on the " History, Present Condition, and 

 Proposed Restoration of Llandaff Cathedral." 



ROYAL SCOTTISH SOCIETY OF ARTS. 



Feb. 28. — George Buchanan, Esq., F.R.S.E., President, in the Chair. 

 ON CAST-IRON. 



At the request of the council, an exposition " On the Strength of Mate- 

 rials, particularly Cast-Iron and Malleable Iron, and their application in 

 the construction of Railway Bridges (Part I.)," was given. By George 

 Buchanan, Esq., President. 



On this subject, so important at the present time from the extensive use of 

 these materials in the construction of bridges for railways, and from the new 

 and extraordinary forms and dimensions which they are now beginning to 

 assume, the council of the Society had requested their President to make a 

 communication on the present state of our knowledge and practice, and this 

 evening he read the first part of this communication, illustrating his subject 

 by various interesting experiments and models, more particularly a large and 

 beautiful model, with drawings and elevations, of the high level bridge across 

 the Tyne at Newcastle, which, through the liberality of Mr. Robert Stephen, 

 son, the engineer of the bridge, he was enabled to exhibit, and to explain 

 the situation, extent, and construction of this great work in all its details. 



Mr. Buchanan began by stating that he did not profess to communicate 

 anything new or original, but would be happy if he could only draw from 



the stores of information which had of late years been accumulating on this 

 subject, under the hands of very eminent, scientific, and practical men, such 

 leading facts and maxims as might prove a safe guide for our practice ; and 

 such truths, when they became known and established on the unerring 

 grounds of experiment and calculation, could not, he thought, be too widely 

 disseminated. The various strains might be all reduced to two kinds, ac- 

 cording as the material is either distended or compressed by any force or 

 pressure. From these two all others arise, and either consist or are com- 

 pounded of them. The tensile strain is the simplest of all, depending neither 

 on the peculiar form of the materials, nor even on the length, but only on a 

 single element, namely, the Section of Fracture. This peculiarity of the ten- 

 sile force was explained and illustrated. In regard to cast-iron, the result 

 of the extensive and interesting experiments by Messrs. Hodgkinson and 

 Fairbairn was given, and it was found from the mean of IG different trials of 

 English, Welsh, and Scotch iron, both hot and cold blast, that this material 

 will sustain about 7A tons per square inch before breaking, the weakest spe- 

 cimen being 6, and the strongest 9 J tons. The limit of fracture, however, can 

 never be approached with safety, not even within a long distance, seeing that 

 this material is liable to unseen imperfections, and, above all, to snap in a 

 moment without distending itself or giving any warning of danger. Mal- 

 leable iron, again, is much superior in tensile strength, and, by its remarkable 

 ductility, inspires confidence in a still higher degree; bears no less, at an 

 average, by various experiments of Telford and Brown, than 27 tons — the 

 weakest 24, and the strongest 29 tons ; but, before the half of this load is 

 applied, it begins to stretch, and continues stretching, up to the limit of 

 fracture. It is, therefore, not only three times stronger than cast-iron, but 

 may be safely loaded with five times the breaking weight, or about eight or 

 nine tons. 



In regard to the strength of compression, this depends also, as long as the 

 length is limited, on tlie same element — the Section of Fracture ; but when 

 a long rod or slender pillar is loaded or compressed, it is liable to bend, not 

 for want of strength, but for want of stability, the least flexure turning it oif 

 its centre, and breaking it by lateral force, deranging entirely the simple law 

 applicable to short lengths. In regard to cast-iron, by far the most satisfac- 

 tory experiments are those by Hodgkinson and Fairbairn. The mean result 

 gives very nearly 50 tons on the square inch — the weakest 361 tons, and the 

 strongest 60 tons. It is thus six times stronger in compression than in dis- 

 tension, and hence it is peculiarly recommended for sustaining any superin- 

 cumbent weight, as in the case of pillars and of bridges, provided the con- 

 struction is such as to resolve the strain arising from the load into a longi- 

 tudinal compression. This is often in our power by proper arrangements, 

 chiefly giving a sufficient height and curvature to the arch; but in cases 

 where, for the want of head-room, the arch is unduly flattened, or resolved 

 into a straight beam or girder, the danger is that we bring the tensile force 

 into play, and then the use of cast-iron is objectionable, or at least requires 

 extreme caution. No direct experiments have been made on malleable iron 

 of short lengths ; but from some facts brought out by Mr. Hodgkinson, its 

 strength appears much inferior to cast-iron, chiefly from ductility, whereby 

 it gives way much sooner under a load. It will bear 27 tons, probably much 

 more, without fracture ; but with 12 tons it yields to the load, contracts 

 longitudinally, and swells out laterally ; and this is another very important 

 fact for our guidance in the use of those diff'erent luaterials. In regard to 

 stone, experiments have been generally made on specimens rather too minute. 

 Like cast-iron, the crushing strength is superior to the tensile, and hence its 

 adaptation for buildings, particularly bridges. Cralgleith stone will bear 2J 

 tons on the inch, or upwards of 400 tons on the square foot ; Aberdeen 

 granite 600 tons. In regard to bricks, he had occasion to make experiments 

 in relation to the great chimney of the Edinburgh Gas Works. It became 

 matter of consideration whether the ordinary brick could withstand the 

 pressure of so lofty a column. Trials were therefore made with a powerful 

 hydrostatic press, not on small specimens, but on the actual brick. The 

 ordinary stock brick was found to bear 140 tons on the square foot, and the 

 common fire-brick 157 tons ; hut the brick of which the chimney is con- 

 structed, consisting of a mixture of fire-clay and ironstone, bore, a single 

 brick on its bed, no less than 140 tons, equal to 400 tons on the square 

 foot. 



The effect of the transverse strain was then considered and illustrated by 

 various experiments and models. This strain is a compound of the tensile 

 and compressive strain, the one part of a beam loaded in the middle being 

 compressed and the other distended, and the beam itself becoming a lever, 

 and acting often with enormous power against its own strength. Hence it 

 became easy to calculate the strength, this being in every case proportional 

 in the first instance to the area of the Section of Fracture, and this original 

 element modified by the length and depth of the beam, diminishing in exact 

 proportion to the length, and increasing in proportion to the depth. 



The transverse strain acting with such severe advantage against our mate- 

 rials, various methods have been contrived for eluding its eftects, and of these 

 none is more remarkable than the principle of the arch, tbe effect of which 

 was illustrated by experipients, and particularly the necessity in flat arches 

 of having secure abutments to resist the horizontal thrust, and this was fre- 

 quently accomplished, where there is sufficient head-room, by uniting the ex- 

 tremities of the arch by strong malleable iron rods, in the same manner as 

 in the case of the roof, the feet of the rafters are united and prevented from 

 spreading by the tie-beams ; and this is the principle, the securest of all, on 

 which the great iron bridge at Newcastle, now in progress, is constructed 

 tbe object of which is to cross the river and valley of the Tyne, on the highest 



