358 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[Ot TOBER. 



hour, and liaving arrived at a perfect welding heat, tlic taUe ia turned to the 

 mark hefore uientioned, and the wheel is slided out on to r.n anvil. This 

 anvil is planed perfectly true on the face, and is larger in diameter than the 

 wheel. .Vliovc the auvil is the hammer, of al)Out 13 cwt.. suspended at a 

 height of about 12 feet, the face of this hammer being phined perfectly true, 

 to correspond with the face of the anvil. As soon as the wheel is placed on 

 the anvil, the hammer is released, falls on the wheel, and perfectly welds it 

 into one entire solid at a single blow. Before pinning tlie wheel together, I 

 put the various parts into a solution of vitriol and water, and, should there 

 he any part corroded, it immediately removes it, so that tliere is nothing but 

 pure iron, and a good welding is easily obtained. The wheel, when cold, is 

 turned up in the usual way. 



'* On JJ'arntinff and Ventilatint/ Buildings." lly Mr. Ritchie. 



The principal oljject of this paper was to call the attention of architects to 

 the construction of houses, with a view to a better provision for heating and 

 ventilation. The author described the method adopted by Sir J. Robison, 

 whose house is warmed by a large supply of air heated to "0', which is al- 

 lowed to issue directly into the lobby and staircase, whicli it heats to 60 

 even in the coldest weather. This heated air is ■'dlowed to enter the sitting 

 rooms freely by concealed apertures over the doors, and tlie vitiated air is 

 carried off tlirough openings in the ceilings by separate flues in each room. 



Mr. Hawkins always found tliat, in the sitting rooms, open fires were re- 

 quired to warm the feet, though not necessary in bed-rooms. — Mr. Hartop 

 agreed, and considered Sylvester's Radiating Stove the best for the purpose, 

 in addition to the general heating ajiparatus. — Mr. Vignoles concurred, and 

 stated that nothing prevented Sylvester's stoves being universally introduced, 

 but their high price. — Mr. Hawkins stated, that, from experience, a large fire 

 with a small supply of air, was the most economical mode of using fuel. — 

 Sir John Kobison stated that, witli the apparatus it\ his house, he can keep 

 his staircase at a temperature of from .'JS' to G2', when the current of heated 

 air was only 61' as it issued from the appai-atus, and that the additional ex- 

 pense caused by his provision for ventilation did not exceed 20/. 



" On the Temperature of most effective condemation in Steam Vessels.' 

 By Mr. J. Scott Russell. 



Much (said llr. Russell) has been said regarding the perfection of the 

 vacuum formed in the condenser of a steam-engine, especially a marine en- 

 gine. It does not appear to be known, that a vacuum may be too good. 

 We hear it boasted every day, by rival engineers, that their engines have the 

 best vacuum. Some boast their vacuum at 27 inches, others at 28, others 

 at 29, some at 30, and at last an engineer appears who boasts a vacuum of 

 30 J inches 1 It is to be regretted that time and talent should be thus wasted. 

 It is a fact of great importance, and it is the result of theory, estabUshed on 

 incontrovertible truth, and confirmed by experiment and by practice, that a 

 vacuum may be too good, and Ijecome a loss instead of a gain. The truth is 

 simply this, and should be known to every engineer: If the larometer atand 

 at 2<i\ inches, the standard of tills cmntrij, the facuum in the condenser is 

 TOO GOOD if if raise in the barometer more than 28 inches nf mercury. This 

 important truth is incontrovertible — it is practically exhibited every day. 

 The following is a simple proof of this doctrine, divested, as far as possible, 

 of a technical form, and put in the shape of an inquiry into the best state of 

 a condenser ; — 



Let /=tlie caloric of water of V. 



c = the constituent caloric of water in the state of steam. 

 e = lhe total force of steam in the boiler, in inches of mercury ; and 

 ,1= the elastic force of steam at the temperature of best condensation, 

 which we seek to discover. 



Then from the law which connects the elastic force of steam with tempe- 

 rature, it follows, that in case of maximum effect, or the temperature of best 

 condensation, — 



I 



el 

 , that IS, .r= — 



= 004 



- = 0-045 



Now^ (• is 1000 J and if the steam in the boiler be at 5 it., above the atmos- 

 phere, or if e=40 inches of mercury, and /= 1, 



■'~iooo 



Again, if tlie steam be at 1\ lb. = 45 inches, 

 45 



''~Ioob 



Again, if the steam be at 10 ft. = 50 inches, 



50 

 .,=___ = 0-05 

 1000 



Hence we find, that the best elasticity or temperature in the condenser de- 

 pends on the elastic force of the steam in the boiler. 



Witli steam of 5 ft. in the boiler, the elasticity of maximum effect in the 

 con(lenser is 93- Fah., and the best vacuum on the barometer is 28. 



With steam of 7v ft. in the boiler, the elasticity of maximum et%ct in the 

 condenser is 95°, and the best vacuum on the barometer is 27-8. 



With steam of 10 ft. in the boiler, the elasticity maximum effect in the 

 condenser is 97°, and the best vacuum on the barotiieter is 27-6. 



In like manner it would be found, tliat with steam of 50 ft. iu the boiler, 



worked expansively, as in Cornwall, the best vacmuu in the condenser would 

 be about 2G. on the barometer. 



It is hoped, therefore, that engineers will not in future distress themselves 

 at finding the vacuum of their condenser much less perfect than the vacuum of 

 others wb.o have obtained 30 andSOS inches at so great loss of fuel and power. 

 To obtain a v.icuum of 29A, with the weather glass at 29-75, and steam at / .1 

 ft., would he to sacrifice four horses' power out of every hundred, in a day 

 when the barometer is as low as 281 inches, the vaomm in the condenser 

 would indicate 26'8. In speaking of the vacuum in the condenser, it would 

 save much ambiguity to indicate the elasticity merely of the steam in the 

 condenser ; thus, if tlie barometer stand without at 29J. and the barometer 

 of the condenser at 28, it might be stated that the steam in the condenser 

 stands at 1 .' , being the point of maximum effort. The indication would con- 

 vey at all times more precise information. 



Mr. Russel stated that the President had just jiut into his hands a com- 

 munication in French on this subject from Mr. Barnes. Instead of a jet play- 

 ing inside the condenser, M. Barnes allows it to nish in suddenly, and then 

 stops it by a slide valve. — Mr. Fairbairn wished to know whether the facts 

 staled by Mr. Russell had been jiractically estabUshed. — Mr. Russell stated 

 how tlie experiment might be made. — ;\Ir. Fairbairn considered tliis a very 

 important subject, as bearing on the economy of fuel, and regretted that Mr. 

 Russell had not given an account of his experiments. — Mr. Russell suggested 

 that Mr. Fairbairn should himself undertake the experiments. — Mr. llodgkin- 

 son considered it very important that experiments should be carried on ; and 

 Mr. Fairbairn, that experiments should be made on steam at all pressures. It 

 was suggested that this was a proper subject to be inquired into by the Bri- 

 tish Association, and it was agreed that the Committee of the Section should 

 discuss the propriety of applying for a grant to pursue the exjieriments. — Mr. 

 Taylor stated that they use plungers in tb.e air-pumps in North Wales ; and 

 Mr. Hartop, that in America air-pump buckets have been made without pack- 

 ing, and found to answer well. — Mr. Roberts stated that he had made engines 

 with solid pistons without packing, both cylinder and air-pump. — Mr. Vignoles 

 mentioned that such solid pistons had been used on some of the first locomo- 

 tive engines on the Dublin and Kingstown Railw.iy. 



" On Timber BriJrjes of a large size, in special reference to Raihrags." 

 By Mr. 'V'iguoles. 



Mr. Vignoles commenced his remarks by stating, that he had, by permis- 

 sion of the committee, selected this subject for illustration and discussion be- 

 foie the Mechanical Section, from the notes of a ivork he was prejiaring for 

 publication, ' On the fieneral Principles aud Economy of Railways,' his object 

 in so doing being to elicit the opinions of liis brother engineers, and to in\ite 

 discussion and obtain information, but especially to direct the attention of all 

 parties interested in the extension of the railway system to a principle of 

 construction which, in many cases, would he found of great advantage in the 

 economy and facility presented for overcoming obstacles, otherwise insur- 

 mountable, within reasonable limits of expense. Mr. Vignoles took a rapid 

 view of the history of timber bridges, tracing their first erection in Germany, 

 then through the United States of America, and back to Great Britain. He 

 also described the difference between the principles of large bridges con- 

 structed with baulks and half-baulks, and of timber arches, forpjed of layers 

 of plank laid over each other, and fastened securely together, and, with felt 

 or other means, to make the joints and beds wholly impervious to water. Mr. 

 Vignoles stated, that the first bridge on this principle in Great Britain had 

 been erected at some place in Scotland, by an ingenious mechanic of that 

 cuuntiT, whose name lie regretted not to he able to state. Tiiis was many 

 years since. The principle had been also made known, particularly of 

 late years, by the timber viaducts erected under the direction of Messrs. 

 Green and Son, of Newcast!e-on-Tyne, wiio had been built several, and had 

 designed more ; and Mr. Vignoles further explained, that Mr. Nicholas Wood, 

 of Killiugworth, who at this time erecting, for the Duke of Buecleugh, a tim- 

 ber viaduct, of great height, aud with large openings. Mr- Vignoles dis- 

 claimed any intention of discussing the question as to whom the merit of 

 orjinality belonged, and observed, tliat he, at present, purposely refrained 

 from any details, as these had Ijeen entered into by Mr. Green both at New- 

 castle and at Birmingham, reserving any remarks on such details for a future 

 occasion, should it present itself. Mr. Vignoles then explained the peculiar 

 applicability of timber bridges or viaducts to the passage of deep ravines, so 

 often met with in hilly and mountainous districts, illustrating his remarks by 

 diagrams. Tlie communications, for example, to be made between the north 

 of El-gland and Scotland would probably have to be sought along son\f of 

 the valleys leading to the passes through the Cumberland Hills, and here, as 

 in many similar districts, engineers iu the habit of considering such lines well 

 knew, that many miles of favourable country for roads or railways were often 

 to be obtained along the sides of sucli ]irincipal valleys, until some unavoid- 

 able appalling obstacle appeared in the passage across some of the lateral 

 openings or ravines. Instances had and might occur where the whole of 

 such a line, otherwise highly desirable, would have to be al'andoned. unless 

 some economical construction were devised to surmouut the difficulty : and 

 here the timber viaduct would most advantageously be introduced, since 

 many feet additional height in the level of the railway would add but little 

 to the expense. He then instanced several places of formidable height, and 

 of various breadths, where he had already designed, or knew of the applica- 

 bility of such constructions. In reference to the expense, he stated, that it 

 was chiefly when extraordinary height and either one arch of great span were 

 required, or where a scries of arches, of large openings, were wanted or could 



