$59 M. CLAPEYRON ON THE MOTIVE POWER OF HEAT. 
will be represented geometrically by the area comprised between the 
axis of the abscisses, the two coordinates C B, D E, and the portion of: 
a hyperbola C E. 
Fig..1. 
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: ea Sse pin it 
A Bi Mi EL INT ae uM x 
Supposing, again, that the body A is removed and that the dilatation 
of the gas continues in an inclosure impermeable to heat ; then a part of 
its sensible caloric becoming latent, its temperature will diminish and 
its pressure will continue to decrease in a more rapid manner and accord- 
ing to an unknown law, which law might be represented geometrically 
by a curve E F, the abscissee of which would be the volumes of the gas, 
and the ordinates the corresponding pressures: we will suppose that the 
dilatation of the gas has continued until the successive reductions which 
its sensible caloric experiences have reduced the temperature T of the 
body A to the temperature ¢ of the body B; its volume will then be A G, 
and the corresponding pressure F G. It will also be evident from the 
same reasoning, that the gas during this second part of its dilatation 
will develop a quantity of mechanical action represented by the area of 
the mixtilinear trapezium D E F G. 
Now that the gas is brought to the temperature ¢ of the body B, let 
us bring them together: if we compress the gas in an inclosure imper- 
meable to heat, but in contact with the body B, the temperature of the 
gas will tend to rise by the evolution of latent heat rendered sensible by 
compression, but will be absorbed in proportion by the body. B, so that 
the temperature of the gas will remain equal to ¢ The pressure will 
increase according to the law of Mariotte: it will be represented geo- 
metrically by the ordinates of a hyperbola K F, and the corresponding 
abscisses will represent the corresponding volumes. Suppose the com- 
pression to be increased until the heat disengaged and absorbed by the 
body B is precisely equal to the heat communicated to the gas by the 
