TBANSACTIONS OF SECTION G. 857 



about the general revolution whicli has therefore only reached its height during the 

 last few years, if, indeed, it is yet reached — certainly it is yet far from complete. 



To turn for one moment to the last year. Since the last meeting of this Section 

 in Birmingham, the second Tay Bridge has been completed, over two miles long, 

 having occupied only five years in construction. 



The Severn Tunnel, one of the most difficult pieces of engineering ever 

 attempted, has been completed and opened for passenger traffic. 



The Forth Bridge, that structiu-e the very thought of which causes those who 

 have seen the place to hold their breaths, and of which the relative size may be best 

 realised from the fact that, held out in arms an eighth part of a mile long, at a 

 height of 200 feet above the sea, as a mother might hold out an infant, are 

 structures no less than the single spans of the Britannia Bridge, 400 feet long. 

 ThLs gigantic structure, the progress of which Section G has watched since the 

 meeting at Southampton, has now attained its full height of 360 feet, although 

 otherwise not by any means fully formed. 



Nor, as you well know, is it by the completion and progress only of great 

 undertakings that this year is marked in the annals of engineering. It will be 

 memorable, particularly in this district, as the year of the commencement of the 

 Manchester Ship Canal. This undertaking, for which there is no precedent in this 

 country, has excited so much interest that it cannot be otherwise than a matter of 

 congratulation that a paper descriptive of this work is to be read before this meet- 

 ing by the engineer, Mr. Leader Williams. 



The completion of the Tay Bridge, the Severn Timnel, the progi'ess of the Forth 

 Bridge, and the commencement of the Manchester Ship Canal in one year and in 

 one country is sufficient assm-ance that, as yet, there is no lack of enterprise or sign 

 of faUing-oif in heroic undertakings ; nor are these by any means the onlj' signs of 

 great mechanical activity, notwithstanding the continual complaints of commercial 

 depression. 



In one direction, in particular, after many years of progi'ess, so slow as to be 

 something like stagnation, there has been a decided advance. The steam engine is 

 such a familiar institution, and has been for so long looked upon as the prime 

 mover of our entire mechanical system, that anything which afi'ects its welfare 

 excites a deeper interest than would a mere mechanical advance. It was therefore 

 with anything but a feeling of pure exultation that we heard and felt the force of 

 predictions a very few years ago that the days of the supremacy of the steam engine 

 were numbered, that it would soon be a thing of the past, only to be found in the 

 museum, a relic like Newcomen's engine and the stone implements by which our 

 children would gauge the depths of mechanical barbarism of the age from which they 

 had emerged. If sentiment be allowed in relation to anything mechanical, it must 

 be with a sense of relief that it is now perceived how, so far from succumbing in the 

 competition with what threatened to be formidable rivals, the only eflect has 

 been to bring about an important step in that internal development of the steam 

 engine, which has been long looked for, but the accomplishment of which had for so 

 long baffled the utmost eiibrts to bring it to a practical issue that it was almost 

 despaired of — at least until it should be brouglit about by that circumstance which 

 we all dread, the scarcity of coal. 



The uppermost step of this advance yet readied is represented by the triple and 

 quadruple expansion engines. These engines, of which the first seem to have been 

 the triple engines of the 'Propontis ' in 1874, designed by Mr. Kirk, the next those 

 of the steam yacht 'Isa,'by Messrs. Douglas and Grant in 1878, and the third 

 those of the ' Aberdeen,' again by Mi\ Kirk, in 1881, rapidly sprang into favour for 

 cargo steamers, in which they have already proved of such advantage as to more 

 than threaten the necessity of another revolution in steamships almost before the 

 last is complete. Each week brings the announcement of some new accomplish- 

 ment in the use of higher ratios of expansion and higher pressures of steam, so that 

 while GO or 70 lbs. was the maximum three years ago, we now hear of 130, 150, 

 and 175 lbs. ; and it is impossible to say to what they have not been carried at 

 the present moment, and with commercial success. 



There can be no doubt but that this latest step, as well as those of the surface 



