ON GASEOUS EXPLOSIONS. 309 



by the fact that the Committee was initiated by the Engineering 

 Hection. On the other hand the work has been by no means entirely, or 

 even mainly, of a practical as distinct from a purely scientific character. 

 Many questions of a kind that might properly engage the attention 

 of the Chemical and Physical Sections have been raised and discussed, and 

 full scope has been given to the varied skill and knowledge possessed by 

 the diSerent members of the Committee, among whom, in addition to 

 engineers, 'there are several whose interests are mainly in the direction of 

 pure science. The test of practical value or interest has only been 

 applied for the purpose of selecting from among the large number of 

 questions arising in connection with explosions those which are proper 

 subjects for investigation by this Committee, not with the idea of 

 limiting such investigation to the practical aspect of these questions. 



Seven meetings of the Committee have been held, and they have 

 been excellently attended. At each meeting one or more notes written 

 by members of the Committee have been presented and have formed the 

 basis of the discussion. The following is a list of these notes : — ■ 



No. 1. General Introduction Dugald Clerk. 



No. 2. Dissociation of Steam and Carbonic Acid . . Dugald Clerk. 

 No. 3a. Measurements of Internal Energy of Gases up to 



1400° C B. Hopkinson. 



No. oB. Explosion Pressures as a Means of Determining 



the Energy Function of Gases . . . . B. Hopkinson. 

 No. 4. Dissociation and Specific Heat of Steam and 



Carbonic Acid, and Comparison of Gas' 



thermometers at very High Temperatures . J. A. Harker. 

 No. 5. The Temperature of the Walls of a Gas-engine 



Cylinder E. G. Coker. 



No. 6. The Deviation of Actual Gases from the Ideal 



State, and the Experimental Errors in the 



Determination of their Specific Heats . . H. L. Callendar. 



The essential feature common to the operation of all gas-engines is 

 the conversion of a mixture of inflammable gases, by combustion or 

 explosion, into a mass which consists in all practical cases of a mixture 

 of steam, carbon dioxide, nitrogen, and excess oxygen. The per- 

 formance of the engine depends primarily on the change in pressure or 

 volume, or both, resulting from this chemical transformation, and on the 

 properties of the products of the transformation after they are formed. 

 It depends in only a secondary degree on the nature of the chemical 

 proce.ss and on the velocity with which it takes place. These matters, 

 important though they must be in any investigation of explosions and in 

 the theory of the gas-engine, are not of the first importance. The 

 foundation must be a knowledge of the properties of the gases 

 enumerated above at the temperatures occurring in the gas-engine — that 

 is, between 1000° and 2500° C. This report, therefore, consists mainly 

 of an analysis of the present state of knowledge on this subject, together 

 with suggestions as to the directions in which further research may be 

 undertaken with the object of advancing it. It will be found, however, 

 that as the mechanism and the velocity of combustion must be taken into 

 account as disturbing factors when applying our knowledge of the gases 

 in the theory of the gas-engine, so they enter into many of the experi- 

 ments on which that knowledge is based, and some discussion of them is 

 indispensable in any criticism of these experiments. 



