THE MECHANICAL EQUIVALENT OF HEAT. 
449 
Results of the Stirring and Radiation Experiments. 
Throughout the remainder of this section the following notation is adopted :— 
W = weight of water {in vacuo). 
M = W + water equivalent of calorimeter. 
p = pressure in annular space. 
t = time of rising 1° C. 
r = rate of revolution of stirrer (revolutions per 1 second). 
K = value of 
cr = rise per 1 second (in degrees C.) due to stirring only. 
p = gain or loss (in degrees C.) per 1 second due to radiation, conduction, and 
convection, when the difference of temperature = I'’ C. 
Q = thermal grms. lost or gained per 1 second by radiation, conduction, and 
convection = Mp, 
Experiments 1 to 31 (see Table XVIII.).—These were all observations taken acros 
the outside temperature only, and were used to establish the relation tr^ = K. 
Experiments 32 to 40.—Are only of use for the same purpose, but they bear out 
the conclusion that tr^ = K. 
As the calorimeter was taken to pieces after Experiment 40 (before any of our 
J experiments were commenced) the results are of no special value. 
Experiments 41 to 50 :— 
W = 103-01 
a- = -000498 
p = -0000743 
Q = -0104. p> — millims. 
Experiments 51 to 57.—(Tables XIX., XX., and XXII.) (Nos. 41 to 54 were used 
in the reduction of J 1 to 4.) 
Experiments 58 to 65.—During this series the value of cr began to show signs of 
alteration. The cause has already been mentioned; flakes of gutta-percha having 
collected at the base of the inner cylinder, the “throw” of the stirrer became less 
regular. Also (as we were not at this time aware of the importance of maintaining 
the pressure unaltered), we both diminished and increased the pressure during this 
series. Fortunately, however, we performed sufficient radiation expeiiments to enable 
us to deduce the probable values of the variables appropriate to the respective J 
determinations. W = 188-065 throughout this series. 
Experiments 58 and 59 :— 
o- = -000354 
p = -000490 
Q - -0134. 2'> 
> J 5 to 7. 
— -40 millim. 
3 M 
MDCCCXCIII.—A. 
