1842.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



.'il.'i 



possible, the liest specimens, but every care had been taken to insure accuracy 

 in the experiments. 



Mr. Hodgkinson said that the average strength of hot blast had been ^h: 

 ■weaker than the cold, but the inferiority was chiefly in the softer irons ; as 

 the hardness increased, the two kinds approached to eijuality, and in the 

 hardest irons the hot blast was the best. He thought his experiments, made 

 without any interest on either side, and with the greatest care, were more to 

 be depended on than experiments made by those who had an interest in the 

 result. 



Professor Vignoles explained, that the question of hot and cold blast had 

 nothing to do with the late contract for cannon balls. 



Ox THE Form of Ships. 



Mr. Scott Russell laid on the table the Rejiori of a Cnmmitlee on the 

 Form of Ships. It contained upwards of 20,000 observations, the result of 

 careful experiments on the resistance to models of ships of more than a 

 hundred different forms and sizes, and extending from small models of 30 in. 

 long, to vessels of 23 ft., GO ft., and 200 ft. 'lo:ig. and above 1000 tons 

 burden. These experiments weie under the general superintendence of a 

 Committee of the Association, consisting originally of Sir John Robison, 

 Mr. Scott ilussell, and Mr. Smith. Unfortunately, the ill health of Mr. 

 Smith's family had altogether deprived the committee of his advice and 

 asssistance, but the observations were personally conducted by Mr. Scott 

 Russell, who had to acknowledge the pleasure he had derived from conferring 

 with bis friend Sir John Robison. with whom he had frequent occasion to 

 consult during the progress of the observations. The smaller experiments 

 had been made in a reservoir in the ground attached to his (Mr. Russell's) 

 residence, and the larger ones in tlie open sea. It was probable that these 

 results, maturely digested, and illustrated by accurate drafts of the forms of 

 the ships subjected to experiment, would be published in such completeness 

 as might be practically serviceable to the naval constructor and mercantile 

 ship-buikler; and he would, therefore, confine the present report to a general 

 account of the objects contemplated in the experiments, and the method by 

 which these designs had been carried out. Several series of experiments 

 have already been made, both by scientific bodies, and by public-spirited men, 

 for the advancement of naval architecture. These had cost large sums of 

 money, and consumed much valuable time and talent. To most of them it 

 had been objected — unhappily not without reason — first, that they had not 

 been conducted with au adequate knowledge of the wants of the constructor; 

 secondly, that the forms of bodies submitted to experiment were by no 

 means such as are used by the ship-budder ; thirdly, that the scale on which 

 these bodies were constructed was too small to claim for the results, as ap- 

 plied on a large scale, any considerable degree of confidence ; fourthly, that 

 it bad not been established by what law the results of experiments on one 

 scale of magnitude are to be transferred to a different scale, either greater 

 or less ; and, fifthly that the apparatus formerly used was liable to errors 

 which it was difticult to eliminate from the results. To ol)viate such objec- 

 tions was one great object in these experiments. Mr. Russell bad contrived 

 a new apparatus, which was so simple and convenient, that a uniform 

 propelling force was obtained, by which vessels of any magnitude might be 

 drawn by a uniform mechanical force along any given distance. The forms 

 of the models employed were not confined to mathematical and arbitrary 

 solids, but were those of such classes of ships as are either actually employed 

 in navigation, or have been proposed for that purpose. Among these were 

 some of the highest reputation. It was found that there were otlier circum- 

 stances besides the form of the vessel which affected the result ; and that 

 the form and dimensions of tlie channel were as important as those of the 

 vessel in determining it. Experiments had been instituted on the largest as 

 well as the smallest scale, to show the law of relation between difi'erent 

 scales. These various modes of experiment were illustrated by reference to 

 drawings and tables which were prepared for publication. As an illustration 

 of the value of giving a proper form to ships, altogether independently of 

 proportion or dimension, the following remarkable experiments were 

 adduced: — -Four vessels, of about 25 ft. length, having all the same dimen- 

 sions of breadth and depth, of the same capacity and weight, and of the same 

 draught of water, were towed together at the same time, under the same 

 circumstances, and at the same velocity. Some writers on naval architecture 

 have asserted that, in such circumstances, vessels would have precisely the same 

 resistance. The forms of these four vessels were not, to an inexperienced 

 eye, very dissimilar : they were all good sea boats, and each of them found 

 its admirers to give its shape a preference over the others. These vessels, 

 alike in all their principal dimensions, and weight, and area of midship 

 section, and draught of water, diflered so much in resistance, that the one 

 had nearly double resistance to another : thus, at 7j miles an hour, the 

 resistances were as follows : — 



No. I. form 56'6 lb. resistance. 



No. II : .. .. 138-5 



No. Ill 102-7 



No. IV 90.2 „ 



All of these were good sea boats, and it was one of the most valuable of 

 these results, that No. I., the form of least resistance, was found also the 

 hest sea boat, the easiest, and the driest. The whole of the observations, 

 comprising luore than 20,000, were in the course of preparation for pub- 

 lication, so that the whole body of the observations would be at the disposal 

 of the Members of the Assocation. It had been the aim of the Committee 



to reduce the whole into the form most immediately conducive to the pur- 

 poses of the naval constructor and mercantile ship-builder, and the drawings 

 had been made on the scale and with the accuracy of the draughts of ships 

 of the largest class. 



Sir John Robison felt it his duty to state to the section, that although he 

 had cordially given Mr. Scott Russell his co-operation in forwarding these 

 experiments, and although Mr. Russell had made frequent use of the plural 

 pronoun, yet that the whole of the merit, both of contriving and designing, 

 and carrying out the system of experiment, was due exclusively to Mr. 

 Russell. 



Mr. Rnssell also explained a model shoving tlie waves in a channel arising 

 from the natuia! channel wave, ai\d the wave resulting from the form of 

 the boat. 



Mr. Williams wished to know how Mr. Russell tested the horse power in 

 the two boats which he had mentioned, as nominal power was not a fair test ; 

 and also whether he had paid attention to the difference in draught after 

 the engines had been put in, the settUng at stern or stem, t^c, as the putting 

 in the engine might make the vessel which had been slowest, when towed, 

 fastest when driven by her own power — a vessel quick in slow water might 

 be slow in a rapid current — in fact, every vessel had its own characteristic, 

 and, therefore, many circumstances entered into the comparison between 

 two vessels. — Mr. Russell said, that a reference to the report would show 

 the steps which had been taken to insure accuracy. Of course in making 

 experiments he had attended to all the circumstances which could introduce 

 in-iccuracy. In answer to Mr. Williams, he would say, that when the vessels 

 were towed, the engines, stores, coals, lic. were exactly the same as when 

 the engines were working ; in fact, they had merely detached the tow rope 

 and started the engines, and it so happened that the vessel which had been 

 fastest in towing was also fastest in saihng with her own engines working, 

 but he did not consider this as aft'ecting the question. 



Prof. Vignoles exhibited some specimens of newly invented carpet tapes- 

 try. He explained that these works were made on the principle of the 

 ancient mosaics, being composed of innumerable transverse sections of 

 woollen threads. No painting, no colouring was used; all the effect was 

 produced by ends of worsteil about J of an inch long standing vertically, one 

 end being seen, and the other cemented by India rubber to a cloth. The 

 exact operation was yet a secret, but he believed that two frames of fine wire 

 or pen'orated zinc (some with even 4000 perforations in an inch) were 

 placed over e.ich other exactly vertically, the distance being only regulated 

 by the height of the room, in the present instance he believed about five 

 feet. The pictuie to be copied being then traced on the top side of the 

 upper frame, a workman passed threads of dyed wool through the corres- 

 ponding holes in the top and bottom frames, of course, as in tapestry, 

 varying his shades and colours until he is satisfied with the efl'ect ; this he 

 can judge of by looking down on tl-.e upper ends of the threads, although to 

 a person looking at the space between the frames, there seems only a con- 

 fused and compact mass of worsted. When the workman is satisfied, the 

 ujipcr ends of the threads are covered with India rubber cement, and a 

 cloth is laid upon them also covered with cement ; the ends of the threads 

 firmly adhere to this cloth. By means of a sharp cutting instrument, the 

 entire mass of threads is now cut through transversely at about j of an inch 

 from the cloth, and this process being repeated, a fresh copy is obtained from 

 every ^ of an inch : in the present frames, being five feet apart, ISO copies 

 can be cut, and as thei-e is no limit to the distance, except the height of the 

 apartment, thousands of copies may be taken of each.. Were this not the 

 case, the invention, however ingenious, would be too expensive to ))e pur- 

 chased except in solitary instances as specimens of curious art : but, from 

 the facility of reproduction, this fabric was likely to come into general use 

 for carpets, rugs, curtains, table and chair covers, &c. ; for carpets and rugs 

 it could be made with a longer nap, so as to give any degree of substance. 



A Description of the Thames Tunnel. By Sir M. I. Brunei, F.R.S. 



Sir M. I. Brunei exhibited a diagram of the exterior elevation of the 

 Thames tunnel, and also a representation of the machinery by which he 

 supported its roof and sides during the process of excavation. He said he 

 had no paper to read, and that his work woidd be very short ; for, altiiough 

 it might be very difficult to describe a work that was to be accomplished, 

 there was little' difficulty in speaking of that which had been completed. 

 All he had to say was simply to point to the representatiorr, and say, that 

 the tunnel which he had erected was like that. The tunnel was about a 

 quarter of a mile in lengtli, and was made under the river Thames. The 

 difficulties were very great, and deemed insurmountable by many learned 

 and scientific men. ' Indeed, the difficulties were much greater than what he 

 himself had at first conceived them to be ; for the groitnd to be excavated 

 was quite difi'erent from that which had been brought up with au augur ia 

 the prehrainary examination of it. However, he was determined to per- 

 severe ; and, notwithstanding the m.tny olrstacles that from time to time 

 presented themselves, he never considered the undertaking impracticable.' 

 Sir M. I. Brunei then directed attention to the apparatus he had devised for 

 sustaining the arch during the progress of the works. It was upwards of 

 60 ft. wide, by 22 ft. high, divided into 12 compartments, each containing 

 three arches, one above another. The top was horizontal. Each compart- 



