194 REPORTS ON THE STATE OF SCIENCE.—1914. 
for chemical contraction. With suitable precautions both methods can 
be made to give consistent results. 
The curve in fig. 13 shows the temperature cycle in a gas-engine 
cylinder determined by Dr. Coker and Mr. Scoble when the ratio of 
air to gas was 735 to 1. The jacket-temperature was 35°6° C., and 
the highest temperature calculated was 1836° C. 
TEMPERATURE CYCLE OF GAS CHARGE.—CONDITIONS. 
Curve Number I.H.P. Bens cee “ Tey dene 
1. 10-24 7:35/1 35:6 
2. 9-96 7:08/1 37-2 
3. 10-11 7-13/1 81-4 
4. 10:36 6-71/1 40-6 
5. 10:36 5-66/1 52°8 
6. 9-74 6-64/1 43-7 
Application of the Work of the Committee to Practical Problems. 
The application of the work of the Committee to practical problems 
can be illustrated in connection with the calculation of the heat ex- 
changed between the working agent and the walls of a gas-engine 
cylinder. 
First Law of Thermodynanucs and the quantities necessary to apply 
it to determine heat lost or gained by the working charge during a 
change of state. 
Let A (fig. 14) be a point on the pressure volume diagram repre- 
senting the state of a working agent with regard to its pressure and 
volume. Let the state change along the path A, B, so that B repre- 
sents the state after the change. Then 
The heat received by the’ The work’ 
: t The change 
ee ea ee ef Maes 08) Sd anit ae Paes |= 
a silos ei be ag oe of ~ | charge J nal energy (+) ‘he agent (1) 
uring the change o per pound on its en- 
state from A to B=Q vironment 
That is, reckoning in thermal units, 
Q=M(Hs—Ey) +4. wt! soc em 
In which Q is measured in pound calories. 
M is the mass of the charge in pounds. 
Ez is the internal energy of the charge in its final state. 
Ea is the internal energy of the charge in its initial state. 
Z is the work done by the agent on its environment measured in foot- 
pounds. 
J = 1,400. 
Earlier it was assumed that the specific heat of the gas used in the 
gas-engine cylinder was constant, and that the change of internal energy 
was determined by the change of temperature only. With this as- 
sumption the first term on the right-hand side of the equation was 
