1850.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



21 



terminated, with his valuable life, on the 2nd of April, 1849, which 

 was shortened by disease, orijjinatingf in over-exertion on the 

 survey in the North of Scotland, and aggravated by fatigue 

 during the great fire at St. Juhn's. where he toiled incessantly for 

 forty-eight liours, in protecting the lives and property of the 

 inhabitants. 



"Colonel Rube was descended from a line of ancestors who had 

 all been in tlie military and naval services; his four brothers were 

 also distinguislied officers, and two of tliem fell gloriously in the 

 service of their country. He was devotedly attached to scientific 

 ])ursuits, and was eminently useful in promoting the object of the 

 societies which he joined, and for this his mathematical acquire- 

 ments and topographical knowledge peculiarly qualified him. He 

 was elected an associate of this Institution in 1838, and served on 

 the council for some years, with great zeal and attention, being 

 continually present at the meetings, and inducing the frequent 

 production of original papers, or presents of charts, &c., for the 

 collection. 



"In the performance of his military and civil duties, his zeal 

 and ability were unbounded; as a sun, a brother, and a friend, he 

 could not be surpassed, and the public estimation in wliich he was 

 held, was fully testified by tlie general mourning for bis loss, at St. 

 John's, Neivfoundland, where he died, and where it was said of him 

 that 'it seldom fell to the lot of a military man to be so beloved by 

 civilians.' The secret of this respect and esteem was the active 

 and untiring benevolence of his character, which was only equalled 

 by his unassuming manner, and the frankness and mildness of his 

 demeanour; and the highest eulogium that can be paid is, tliat 

 'those who knew him best, esteemed him most.'" 



The thanks of the Institution were voted unanimously to the 

 President, Vice-President, Members, and Associates of Council, 

 to the Auditors, Scrutineers, and the Secretary, for their attention 

 to the interests of this Institution. 



The President returned thanks very briefly, and on retiring from 

 the Chair, after holding it most worthily for the two past years, 

 he recommended to the members bis successor, Mr. Cubitt, whose 

 active energy and high position in the profession, rendered him 

 every way fit to occupy the Chair of such a society. 



The address was very warmly received, and it was proposed to 

 the council, to consider by what means the eminent ])ast Presidents 

 could be enabled to continue their valuable services, in conjunction 

 with the acting council. 



ROYAL SCOTTISH SOCIETY OF ARTS 



Nov, 26, 1849. — Thomas Grainger, Esq., President, in the Chair. 



The following eomniunications were made: — 



1. At the request nf the Council an Experimental Exposition was given, 

 containing Ins "Concluding obaerva tions on the ^Strength of Materials^ as ap- 

 plicable to tlie construction of Cast or Wrouy/it-Iron Bridges, and on the 

 Conway and Britannia Tubular Bridges (Part II.), being an account of the 

 method of raising the Tubes of these. Bridges." liy George Buchanan, 

 Esq., r.R.S.E. 



In this concluding paper Mr. Buchanan commenced by giving the result of 

 an interesting experiment, made since the former evening, on the transverse 

 strength of Caithness pavement. The results of the experiments already 

 shown on slabs 9 inches broad, 3 feet deep, and 3 feet long, were as fol- 

 lows: — 



Hailes 7941b. 



Craigleitli 1148 



Arbroath 1848 



The Caithness pavement was rather less in dimensions than the others, 

 being only Scinches broad instead of 9 inches, and 2J deep in place of 3 

 inches. From the previous experiments on the tensile and compressive 

 strength of Caithness pavement, he had hardly expected it would equal the 

 Arhroalh; but it was found greatly to exceed it. After piling on stones and 

 brick to the extent of 25 cwt., the frame, being of a temporary nature, gave 

 way, but with all the concussion the stone was not broken ; and on 

 trying it again with a stronger frame, it carried for nearly half a minute 

 29 cwt. 1 qr. 15 lb., and then gave way. This specimen, he understood, was 

 from the hardest of the quarries, and be has no doubt there are considerable 

 diversities, which shows the importance of these experiments, and of con- 

 tinuing and extending them with every opportunity. The unit of strength 

 from these experiments is easily deduced by taking the breaking weight of 

 each specimen, multiplying it by the length, and dividing by the depth and 

 by the section of fracture. The results are as follows :— 



Units of strength. 



Hailea 3i3 lb. 



Cralnleilh SIO* 



Arbroath 821 



Caithness loUO 



Mr. Buchanan then proceeded to complete his description of the lifting 

 of the Britannia Tubes. 



The main process of lifting was completed previous to his visit, and the 

 tube raised to its place; but as it still required some finishing adjustments in 

 the bed-plates, he had an opportunity, when there, through the kindness and 

 attention of Mr. Clarke, of witnessing this great and interesting operation ; 

 and it was truly gratifying to observe the simplicity and perfect action of the 

 machinery by which it was accomplished, the movement of the small engine 

 and piston being smooth and easy, while the gigantic mass of the tube rose 

 slowly and majestically to the place required. The ascent to the lifting 

 machinery is first by long ladders in the dark hollow or void within the 

 Britannia Tower. This brings us to the level of the bottom of the tube, and 

 from thence the ascent to the top is by similar ladders in open day, resting 

 on the sides of the tube, and, when ascended, we attain an elevation of 133 

 feet above high-water mark, and nearly 150 feet above low water ; and in 

 walking along the top of the lube, between the towers, there being no rail- 

 ing, the gusts of wind at such an elevation appear at first rather alarming, 

 yet it is curious to remark, that immediately on the surface of the tube, and 

 for several feet above it, a comparative calm prevails, owing to the wind im- 

 pinging upon the sides and flying over head ; so much so, that he was 

 informed, even in a very strong wind, a li^ihted candle could he carried near 

 the surface nf the tube all the way without being extinguished. 



He then illustrated the process of lifting by drawings on a large scale, and 

 models of the Bridge and Towers, and an enlarged model of the lifting ap- 

 paratus; all which exhibited very clearly the whole details of the operation. 

 It is accomplished by hydrostatic power, worked by steam-engines, which 

 are all erected and fixed on the top of the towers, the engines giving motion 

 to small force-pumps by which water is forced witii an intense compressioti 

 into the interior of large cylinders, which again communicate this pressure 

 with increased effect on the enlarged surface of the pistons or rams which 

 move up and down within these cylinders, and at each ascent are capable of 

 bearing a most enormous load resting on the top. In the Britannia Tower 

 there are two of these cylinders and rauis, standing about 6 feet apart, and 

 carrying a vast beam of cast-iron, resting at each extremity on a shoulder on 

 the top of the ram, and extending between them, in one solid mass, 4 feet 

 deep, and a proportional thickness, and strengthened along the bottom by 

 very strong malleable iron ties. 



The rams being made to rise simultaneously, the whole beam rises with a 

 slow and regular motion, bearing up whatever may be attached toil. The 

 pressure of the water within the tubes is capable of being raised as high as 

 450 atmospheres, or 6,700 lb., or 3 tons and upwards per square inch; and 

 the area of each ram, which is 18 inches diameter, being 260 inches, the 

 combined effect of the two rams is capable of lifting upwards of 1,500 tons. 



But all this machinery and power would he of no avail, unless it hail a 

 proportionally firm and secure place to stand on, and to bear up the weight 

 of the machinery itself, and in addition to this, the 1,500 tons which it is 

 capable of lifting. For this purpose, two very massive beams or girders, not 

 of cast-iron, but of malleable iron, are extended across the recess or opening 

 in the tower, resting at each extremity on strong masses of cast-iron, or wall 

 boxes built solidly into the masonry. These beams are 21 feet long, 4 feet 

 deep, and 18 inches thick, consisting of a mass of plates laid together and 

 firmly bolted, and the whole, being of malleable iron, gives great additional 

 security and confidence. 



To communicate the above power of the presses to the tube, which, after 

 being floated, is still situated 120 feet below the level of the pumps and 

 presses, two enormous chains, consisting of long and shoit links ot fiat plates, 

 descend from the cross beam or head which rests upon the rams, down to 

 the extremity of the tube to which they are attached; very particular ar- 

 rangements are necessary for attaching these chains to the tubes. For this 

 purpose, the extremities of the tube are strengthened at the sides by three 

 strong cast iron pillars or frames, standing upright on each side of the tube, 

 and rivetted to the thin sides of it, and connected by cross beams to the top 

 and bottom, so as to form each one entire rectangular frame, fitting the interior 

 of the tube. These frames are necessary, in the first instance, for strengthen- 

 ing the tube itself; for, strange as it may appear, though the tube carries an 

 enormous load in the centre, yet at the extremities where it rests on the 

 piers, and where the whole pressure is thrown and concentrated upon the 

 thin sides, it would not, without aid, carry its own weight; it would fall to 

 pieces in a moment by the accumulated pressure ; and it was found, on th.; 

 remarkable occasion of the bursting of the cylinder, though the tube only 

 descended a few inches, such was the efl^ect of the concussion, that these 

 pillars and frames were fractured and shivered to pieces. It is by these 

 frames, then, that a secure attachment is obtained for the lifting chains, and 

 for this purpose three additional cross-beams are extended at intervals be- 



* It was here sugfrested by Mr. Black, architect for Heriot's Hospital, that these expe- 

 riments would probably not give a fair criterion of Craigleith stone, as he conceived the 

 strength would be very much diminished by the hammering and chisseling necessary to 

 reduce it to a 3-inch thickness, and that if the trials were made upon larger masses a 

 greater unit of strength would, be thought, be found applicable to them. It was ex- 

 plained, however, that the above specimen was not from the liver rock of the quarry, but 

 from the common rock ; and, as afterwards stated by Mr. Notman, who furnished all the 

 specimens, from what is called the pavement flakes, which run in parallel beds from 4 to 

 Ij inches thick, the same way as the other pavements. It was -1^ inches thick when taken 

 out of the quarry; and the reduction, Rlr. Buchanan did not think could aflfect the 

 strength on the above general result. The hver rock would have borne less than the 5i:e- 

 cimeu. 



