226 On the Expenditure of Heat in the Hot-air Engine. 
ditional consumption of heat, with corresponding depression of 
temperature. The expression, 
120:0456 MK, =20:-97 MK,,, 
M being equal to 47 lbs. instead of 70, will give us only 986° F. 
@2Pplied to one pound of water. But the subsequent expansion, 
according to Poisson’s formula, (2,) will give a temperature of 
322° at the end of the stroke, which is a falling off of 128, from 
the maximum, 450°. This is converted into mechanical effect, 
and this the regenerator cannot save. 
128 MK, = 94-44 MK,=22-44 MK,,. 
Hence, owing to the expansion after cut-off, there is an additional 
consumption of heat at every stroke sufficient to raise the tem- 
perature of a pound of water, 22°-44 x 47 = 1054°-68, This amount 
added to the former gives 2040°-68. But 724068 _ 1.787 Ibs. of 
1142 
water =49-41 cubic inches, which, converted into steam at 212°, 
is adequate to raise 102914 lbs. one foot, or 17152 pounds 
through the six foot stroke. But we have seen that the power 
of the hot air engine, of the proportions and dimensions supposed, 
is represented by 74698 pounds raised through the same distance, 
hich makes the advantage im favor of air, as 1: 4°35. we 
allow to the steam the benefit of the same amount of expansion, 
its effect will be (assuming 7 for steam to be the same as for air, 
equal to 23050 Ibs. during the stroke,t reducing the foregoing 
ratio to 1:3-24. 
But it has been shown, in the article before alluded to, that 
these are not the proportions most favorable to the efficiency 
of the air engine. If 1:m represent the ratio of capacities of 
working and supply cylinder, and 1:2 be the ratio of the full 
stroke to the fractional part up to cut-off, then should be 
greater than unity. 
This proposition will, however, be understood to be asserted 
only in reference to the theoretic consumption of heat, as com- 
pared with the power developed, and to the amount of available 
power to be obtained from a working cylinder of definite dimen- 
sions. It is entirely independent of the question as to what vol- 
ume of air can be heated by the furnace and regenerators, SO 2S 
* Capt. Eriesson says that the fur 1 bihie d : perature. 
If it does, (which is no doubt impossible, however,) the power of the engine will be 
greater, but the expenditure of i greater also. In the present case, it W 
mer number into the calculation, since the maximum temperature cannot possibly 
sustained during the expansion. The furnaces may, nevertheless, somewhat check 
the depression. 
Determined by the method. pre in a following article, and not by the imper- 
y engineers, etic 
amount to 174°, instead of 128°. It would be folly, however, to introduce the x 
t 
fect modes commonly employed 
