54 TRANSPIRATION IN A DESERT PERENNIAL. 
temperature determination, 7. e., in the turpentine, their specific heat was 
determined last; meanwhile readings for their initial temperature were taken 
as follows. 
Turpentine at air-temperature was placed in two calorimeters and the 
whole allowed to come to equilibrium on a shaded stand near the tree to be 
used. Leaves were quickly severed from their twigs by means of wooden- 
tipped forceps and then placed on white glazed paper, from which they were 
transferred with all possible speed to one of the calorimeter cups, the other 
being kept for a control. The contents of both calorimeters was kept in 
constant slow motion by use of the stirrers. Temperatures were read every 
half minute before and after the introduction of the leaves. 
A determination of the specific heat of the leaves was made by heating 
turpentine to about 30° C., then placing it, in the same careful way as above, 
into the turpentine and leaves just used in the temperature readings. Tem- 
peratures of the contents of both liquids were taken accurately just before 
and after the mixing. The specific heat of the leaves was calculated from 
the equation, 
[A (Sa) +L (Se) +C] [Ta— Tc] = B(Sb) (Te— Tb) (2) 
where 
A=weight of turpentine containing leaves. 
B=weight of turpentine added to A, and leaves. 
Sa, Sb=specific heat of turpentine. 
L=weight of leaves. 
Se=specific heat of leaves. 
Ta=initial temperature of A and L. 
Tb =initial temperature of B. 
Tc=temperature of mixture. 
C=heat equivalent of the calorimeter. 
After the value of Se had been found it was substituted in the equation 
[A(Sa)-+C] [Ta—Tc]=L(Se) (Tc— Tb) (3) 
where 
A =weight of turpentine prepared to receive leaves from the plant. 
L=weight of leaves. 
Ta= initial temperature of turpentine. 
Tb =initial temperature of leaves. 
Tc=temperature of mixture. 
Se and C=same as in previous cases. 
Since Tb is now the only unknown quantity in equation 8, the original 
temperature of the leaves can be easily calculated. 
