ON THE MECHANICAL EQUIVALENT OF HEAT 



369 



T= T {1 + 373 (b( w - M - (273+ T}(V - b)\, 

 T= T' {I .000858 + (273+7 v )(& b')\ t 



T= -99975 T approximately between and 40. The last is true 

 within less than -j-gVir f a degree. 



The two bulbs of the air thermometer used were from the same piece 

 of glass tubing, and consequently had nearly, if not quite, the same 

 coefficient of expansion. 



In the reduction of the barometer and other mercurial columns to 

 zero, the coefficient -000162 was used, seeing that all the scales were 

 of brass. 



In the tables the readings of the thermometers are reduced to 

 volumes of the tube from the tables of calibration, and they are cor- 

 rected for the pressure of water, which increased their reading, except 

 at 0, by about 0-01C. 



TABLE IX. TABLE OF CORRECTIONS. 



The order of the readings was as follows in each observation: 1st, 

 barometer; 2d, cathetometer; 3d, thermometers forward and backward; 

 4th, cathetometer; 5th, barometer, &c., repeating the same once or 

 twice at each temperature. In the later observations, two series like 

 the above were taken, and the water stirred between them. 



The following results were obtained at various times for the value of 

 a with the first bulb : 



0036664 



0036670 



0036658 



0036664 



0036676 



Mean a = -00366664 



24 



