356 



NATURE 



[August u, 1892 



it was pleasant to receive the request of the Council to preside 

 at the meetings of Section G, even though much of the pleasure 

 was due to its unexpectedness. I ventured to believe I might 

 accept the honour gratefully, trusting to your kindness to assist 

 me in fulfilling its obligations. Amongst engineers there are 

 many with greater claims than I have to such a position, and 

 who could speak to you from a wider practical experience. 

 Here in Section G, I think it may be claimed that the profession 

 of engineering owes much to some who from circumstances or 

 natural bias have concerned themselves more with those scien- 

 tific studies and experimental researches which are useful to the 

 engineer, than with the actual carrying on of engineering opera- 

 tions. Here, at so short a distance from the University where 

 Rankine and James Thomson laboured, I may venture to feel 

 proud of being amongst those whose business it has been rather 

 to investigate problems than to execute works. 



The year just passed is not one unmemorable in the annals of 

 engineering. By an effort remarkable for its rapidity, and as an 

 example of organization of labour, the broad gauge system has 

 been extinguished. It has disappeared like some prehistoric 

 mammoth, a large-limbed organism, perfect for its purpose and 

 created in a generous mood, but conquered in the struggle for 

 existence by smaller but more active rivals. If we recognize 

 that the great controversy of fifty years ago has at last been de- 

 cided against Brunei, at least we ought to remember that the 

 broad gauge system was one only of many original experiments 

 due to his genius and courage, experiments in every field of en- 

 gineering, in bridge building, in locomotive design, in ship con- 

 struction, the successes and failures of which have alike enlarged 

 the knowledge of engineei-s and helped the progress of 

 engineering. 



The past year has seen the completion of the magnificent 

 scheme of water supply for Liverpool, from the Vyrnwy, car- 

 ried out from 1879 to 1885 by Mr. Hawksley and Mr. Deacon, 

 and since then completed under the direction of the latter engin- 

 eer. This is one of the largest and most striking of those works 

 of municipal engineering rendered necessary by the growth of 

 great city communities and made possible by their wealth and 

 public spirit. For the supply of water to Liverpool, the largest 

 artificial lake in Europe has been created in mid- Wales, by the 

 contruction across a mountain valley of a dam of cyclopean 

 masonry, itself one of the most remarkable masonry works in 

 the world. The lake contains an available supply of over 12,000 

 million gallons, its size having been determined not only to sup- 

 ply forty million gallons daily for the increasing demand of 

 Liverpool, but also to meet the necessity imposed by Parliament 

 that an unprecedentedly large compensation, amounting to ten 

 million gallons daily and fifty million gallons additional on 

 thirty-two days yearly, should be afforded to the Severn. The 

 masonry dam, though a little less in height than some fof the 

 French dams, is of greater length. It is nearly double the 

 length of the great dam at Verviers. ^ Athough masonry dams 

 were an old expedient of engineers, it is in quite recent times, 

 and chiefly in consequence of the scientific investigations of 

 French engineers, that they have been revived in engineering 

 practice. Since the completion of the Vyrnwy dam, another 

 very large dam, the Tansa dam, has been completed in Bom- 

 bay. This dam has a length of two miles and a height of 118 

 feet, and it is 100 feet thick at the base. The reservoir will sup- 

 ply 100 million gallons per day. In the United States a still 

 greater work of the same kind has been commenced on the Cro- 

 tonriver, in connection with the water supply of New York. This 

 dam will have a length of 2000 feet, and a height of 285 feet. 

 Its greatest thickness will be 215 feet. It will be very much the 

 boldest work of its kind. 



Returning to the Liverpool supply, the water taken from the 

 lake at the most suitable level into a straining tower provided 

 with very complete hydraulic machinery, passes through the 

 Hirnant tunnel, and thence by an aqueduct, partly consisting of 

 rock tunnels, partly of pipes 39in. to 42in. in diameter, sixty- 

 eight miles in length, being the longest aqueduct yet construc- 

 ted. The crossing of the Mersey by an aqueduct tunnel has 

 proved the greatest engineering difficulty to be surmounted. 

 The tunnel has been carried through layers of running sand, 

 gravel, and silt. At first slow progress was made, but later, 

 by the adoption of the Greathead system of shield, with air 



I The length of the dam from rock to rock is 1172 feet. Height from 

 lowest part of foundation to parapet of carriage way, 161 feel. Height from 

 bed of river to overflow sill, 84 feet. Thickness of masonry at base, 120 

 feet. 



locks and air-compressing machinery, as much as fifty-seven feet 

 of tunnel were driven and lined in one week. The whole work 

 is now complete, and Liverpool has available an extra supply of 

 very pure water, amounting to forty million gallons daily. 



A scheme of water supply for Manchester from Lake Thirle- 

 mere in Westmoreland, on an equally large scheme, is approach- 

 ing completion. Birmingham is likely to carry out another 

 work of the same kind. And London, at a greater distance 

 from pure water sources and under greater difficulties from the 

 complexity of existing interests, has come to realize that, within 

 fifty years, a population of \2.\ millions will probably have to 

 be provided for. To supply such a population, a volume of water 

 is required ten times as great as the whole available supply from 

 Lake Vyrnwy. 



Here in Edinburgh one remembers that the birth-place of the 

 steam-engine is near at hand. A century and a quarter ago 

 James Watt made an invention which has profoundly influenced 

 all the conditions of social, national, commercial, and industrial 

 life. It is due to the steam-engine more than to any other single 

 cause that the population in this country has tripled since the 

 beginning of the century, and that we have become dependent 

 on steam-power for fuel, for transport, for manufactures, in 

 many cases for water supply, for sanitation, and for artificial 

 light. From some German statistics it appears that there are 

 probably now in the world, employed in industry, steam-engines 

 exerting 49 million horse-power, besides locomotives exerting 

 six million horse- powA-. Engines in steam-ships are not 

 included. The steam-engine has become a potent factor in 

 civilization, because it places at our disposal mechanical energy 

 at a sufficiently low cost, and the efforts of engineers have been 

 steadily directed to diminishing the cost at which steam-power 

 is produced. Members of one great branch of our profession 

 are much concerned in the production of mechanical energy at a 

 sufficiently cheap rate. They require it in very large quantity 

 for transformation into light and for re- transformation into 

 mechanical energy under conditions more convenient than the 

 direct use of steam-power. Perhaps it will not be inappropriate 

 if in Section G I first discuss briefly some of the causes which 

 have made the steam-engine inefficient and the extent to which 

 we are getting to a scientific knowledge of the methods of evad- 

 ing them. I propose then to consider some of the methods of 

 economizing the cost and increasing the convenience of 

 mechanical power by generating it at central stations and dis- 

 tributing it, and lastly, how far means of transporting energy 

 are likely to make available cheaper sources of energy than 

 steam-power. 



Let us go back for a moment to James Watt. The most dis- 

 tinct feature about the invention of the steam-engine is that it 

 arose out of studies of such questions as the relation of pressure 

 and temperature of steam, the heat absorbed in producing it, 

 and its volume at different pressures. 



Armed with this knowledge. Watt was able to determine 

 that the quantity of steam used in a model atmospheric engine 

 was enormously greater than that due to the volume described 

 by the piston. There was waste or loss. To discover the loss 

 was to get on the path of finding a remedy. The separate 

 condenser, by diminishing cylinder condensation, annulled a 

 great part of the loss. So great was Watt's insight into the 

 action of the engine that he was able to leave it so perfect that, 

 except in one respect, little remained for succeeding engine 

 builders, except to perfect the machines for its manufacture, to 

 improve its details, and to adapt it to new purposes. Now it 

 very early became clear that there were two directions of advance 

 which ought to secure greater economy. Simple mechanical 

 indications showed that increased expansion ought to ensure 

 increased economy. Thermodynamic considerations indicated 

 that higher pressures, involving a greater temperature range of 

 working, ought to secure greater economy. But in attempting 

 to advance in either of these directions, engineers were more or 

 less disappointed. Some of Watt's engines worked with 5 lbs. 

 of coal per indicated horse-power per hour. Many engines 

 with greater pressures and longer expansions have done but 

 little better. The history of steam-engine improvement for a 

 quarter of a century has been an attempt to secure the advan- 

 tages of high pressures and high ratios of expansion. The 

 difficulty to be overcome has proved to be due to the same 

 cause as the inefficiency of Watt's model engine. The separate 

 condenser diminished, but it did not annul, the action of the 

 cylinder wall. The first experiments which really startled 

 thoughtful steam engineers were those made by Mr. Isherwood, 



NO. I 1 1 



VOL. 



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