Mr. Foulis asked what proportion the power indicated on the diagram bore to the power indicated on the brake in the atmospheric engine.

Mr. Holt said unfortunately he had not any figures with him which would give this information; and it was so long since he had anything practically to do with this form of engine, that he should not like to speak from memory. He might add that the largest size of gas-engine made (of about 100 horse power indicated) was at work at Messrs. Edwin Butterworth and Co.'s, of Manchester. It was now driven by ordinary coal gas; but Dowson plant was to be put up very shortly in order to reduce the cost of working, which, though not excessive, would be still more economical with the Dowson gas - probably only about 30s. per week. The present cost was about £4 per week, though it was not working always at full power.

Mr. T. Holgate (Batley) said he thought it was generally understood, by those who had studied the subject, that the adoption of compression of the gaseous mixture before ignition had, so far, more than anything else, contributed to the improved working of gas-engines. This fact had not been sufficiently brought out in the paper, although Mr. Lane had clearly indicated some of the directions in which further improvements were likely to obtain. Gas engineers were largely indebted to Mr. Dugald Clerk for the statement he had made of the theory of the gas-engine.4 Mr. Lane had given some figures, arrived at by Messrs. Brooks and Steward, from experiments made in America; but, prior to these Mr. Clerk had given others which were in the main in accordance with them. Professor Kennedy had also made experiments, the results of which agreed with them.5 The extent of the loss by the cooling water was thus well ascertained; and it was no doubt by a reduction of this loss that further improvement in the working of gas-engines would eventually be obtained.

Mr. J. Paterson (Warrington) expressed his appreciation of the paper, as one of exceptional interest and value. He said he did not rise with a view to make any observations thereon. The analysis of first principles required more matured consideration and thought than could be given to it here. The opinion, however, he had formed of the paper placed it beyond the reach of criticism. It was now many years since his attention had been drawn to the name of Denny Lane; and everything that had come from his facile pen conveyed sound scientific conclusions. The paper to which they had just listened was no exception. It was invested with great interest, and would be regarded as a valuable contribution to the Transactions of the Institute.

Mr. Lane, in reply, thanked the members for the kind expressions used with respect to his paper. His object in writing it was that any one who had not paid any attention to the subject before should be able to understand thoroughly the principles on which gas and hot-air engines operated; and he believed any one who read it with moderate care would perfectly understand all the essential conditions of the gas-engine. He might mention that not long after the thermo-dynamic theory was so far developed as to determine the amount of heat converted into power, a very eminent French Engineer - M. Hirn - conducted some experiments on steam-engines at a large factory, and thought he could account for the whole heat of combustion in the condensed water and the heat which passed away; so much so that he actually doubted altogether the theory of thermo-dynamics. However, being open to conviction, he made further experiments, and discovered that he had been in error, and ultimately became one of the most energetic supporters of the theory. This showed how necessary it was to be careful before arriving at a conclusion on such a subject.

He had endeavored, as far as the nature of the case allowed, to avoid any scientific abstractions, because he knew that when practical men came to theory - x's and y's, differentials, integrals, and other mathematical formulae - they were apt to be terrified.

The President said it was like coming down to every day life to say that it was important that gas managers should be familiar with the appliances used in the consumption of gas, and should be able, when called upon, to give an intelligent description of their method of working. A study of Mr. Lane's paper would reveal many matters of interest with regard to this wonderful motor, which was coming daily more and more into use, not only to the advantage of gas manufacturers, but of those who employed them.

[1]

A paper read before the Gas Institute, Manchester, June, 1885.

[2]

See Journal, vol. xxxv, pp. 91, 133.

[3]

Ibid., vol. xliii., pp. 703, 744.

[4]

See Journal, vol. xxxix., p. 648.

[5]

Ibid., vol. xl., p. 955.