296 Mr. Dugald Clerk [Jan. 29, 



external air temperature nearly 20^ C, and the water jacket tempera- 

 ture 27° C. In the engine experimented on the compression was 

 somewhat low, and at full load the mixture used was verj rich, 

 the proportion of gas to air in the entering charge being one to 5 * 8. 

 Other measurements were made at a point 80 degrees crank angle 

 from the beginning of the compression stroke, and with a compression 

 pressure of 18*5 lb. per inch absolute at the point of measurement, 

 the temperature here was found to be 111° C. With a richer mix- 

 ture and the engine running at a lower speed, the corresponding 

 temperature was 180° C. Calculating from these suction and com- 

 pression temperatures values, Callendar and Dalby find with a rich 

 mixture flame temperature at the point C as 2500° C, mixture drawn 

 into the engine being one of gas to 5 • 8 of air. With one of gas to 

 7 • 1 of air the temperature at C is nearly 2250° C. The exhaust tem- 

 perature — that is, the temperatures at the point D — in the case of 

 the rich mixture was 870° C, and in the poorer mixture 800° C. 

 Professors Callendar and Dalby are continuing their experiments with 

 improved apparatus. 



Clerk has also made temperature determinations in gas engine 

 cyHnders for experimental purposes by another method of determina- 

 tion of suction temp)erature. It is only applicable, however, to 

 isolated indicator diagrams from single explosions and expansions 

 taken under experimental conditions, where the engine experimented 

 on is driven by means of an electric motor. The arrangement 

 adopted is shown diagrammatically at Fig. 24. In these experiments 

 an engine of 9 inches cylinder and 17 inches stroke was used. It is. 

 indicated at A. The inlet valve is connected to a reservoir B, and 

 the engine is driven by means of an electric motor C. The reservoir 

 B is filled with the particular mixture of gas and air which is to 

 be experimented upon, and a thermometer D is placed in the pipe 

 communicating between the cylinder A and the reservoir B. The 

 engine valves are controlled by trip gear, so that the inlet may be 

 held up until wanted. After the reservoir B and the cylinder A and 

 the connecting pipes have been filled with the mixture to be experi- 

 mented upon, the engine is driven by the electric motor at a specified 

 speed, and the gases are alternately taken into the cylinder from 

 B and discharged into B from the cylinder. The charge thus enters 

 and leaves the cylinder many times under pressures only slightly 

 above atmosphere, and so repeatedly passes over the thermometer D. 

 That thermometer, which is one of the ordinary mercury type, attains 

 a certain temperature, which remains fairly constant after a certain 

 number of revolutions. The temperature is a mean between that of 

 the gases passing from B to A and passing from A to B. This 

 temperature then is taken as the temperature of a charge within the 

 cylinder. The cylinder is kept by water jacket at about atmospheric 

 temperature. In this way Clerk believes the temperature of the 

 charge to be determined to within 1° C. Trip gear is applied at the 



