W. A, Norton on Ericsson's Caloric Engine. 401 
originally filled the supply cylinder at 15 Ibs. pressure, will oc- 
cupy one-half the space at 30 Ibs. pressure. Now, while the 
communication between the receiver and the working cylinder 
continues open, that is during the 3 stroke, if we disregard the 
eakage, &c., the same quantity of air, at the same pressure 
of 30 lbs., will flow from the former to the latter. It is capable 
of filling a space equal to one-half of the supply cylinder, or 
what amounts to the same, one-third of the working cylinder, at 
e same temperature, without any change of pressure; there- 
fore in expanding to fill two-thirds of the working cylinder its 
€xpansive force will be reduced to 15 lbs. ‘To compensate for 
this it is only necessary that its temperature, as fast as it flows in, 
encld be elevated 480°, when its expansive force will be retained 
at 30 Ibs, 
A similar explanation may be given for any other supposed 
Pressure and temperature, and the question of the leakage may 
be considered from this point of view. 
_ithas been stated that the cut off, whatever may be the rela- 
live size of the two cylinders, should be so adjusted that the por- 
tion of the working cylinder into which the air is admitted while 
valve remains open, will be equal in volume to the whole 
Supply cylinder. To show this, we will at first leave the leakage 
out of view, and denote the fractional part of the stroke answer- 
mg to the cut off supposed, (in the present engines 3) by a, and 
alarger fraction of the stroke, answering to a different cut off, by 
b Let 6 be m times greater than a. Now, if we conceive the 
fractional cut-off-stroke to be less than a, the actual working pres- 
ini , the mean effective pressure, for t 
Whole stroke, will be less than when a is used. — If, on the other 
and its working force will be vibes 2 (supposing working temper- 
480° +.32°); whereas, for the cut off a the force will 
ature to be i 
be 15 x2, and in the subsequent expansion from a to 6, the mean 
ee throughout the fractional stroke 4 will be greater than 
Pan since this will be the actual force after the expansion to b. 
, the same will be true if we take the leakage into account; 
for suppose the leakage to reduce the pressure of the air that fills 
4; before it is heated, to ad then when heated 480° the pressure 
% _™m 
becomes = 2, which we will put equal to k. Now, if we sup- 
Pose, as before, the cut off to be increased from a to b, the force 
Szrus, Vol. XV, No. 45.—May, 1853. 52 
