01^ THE MECHANICAL EQUIVALENT OF HEAT. 
395 
Col. 3 gives the heat generated,as calculated from the formula (W^ —Wj) (Tg— T^), 
all corrections being omitted. 
Col. 4 gives the terminal corrections, for which, as I have said, the necessary 
observations were always taken. 
Cols. 5 and 6 give respectively the mean differences of temperature observed 
between the stuffing-box and the top and bottom brasses of the main 
shaft bearing. 
The quantities in brackets are not actually observed differences, but were deduced 
in the manner to be hereafter explained (par. 43). 
These differences are 4- or — according as the stuffing-box was hotter or colder 
than the adjacent bearing. 
Col. 7 gives the mean difference of temperature observed between the brake and 
the surrounding air. These differences are, of course, all positive. 
The quantities given in the part of the table headed “ differences” are in every case 
the remainders which are left on subtracting the corresponding quantities under the 
heading “ light trials” from those appertaining to the “ heavy trials.” 
In the last column are given the values of K, obtained by dividing the vnrk 
occurring under the heading differences, by the heat, to which has hist l)een added 
the terminal correction. 
The conditions under which each series of trials given in Table A was run are 
enumerated below. 
In every case the engine speed was 300 revolutions per minute, as read on the 
speed-gauge. 
In all heavy trials the moment was 1200 ft.-lbs., with the exception of Series IV., 
in which the moment was 1244‘12 ft.-lbs. 
In all the light trials the load was 600 ft.-lbs. 
Series I. 
35. This series contains trials Nos. 1 to 11, No. 5 being omitted on account of an 
accident to the revolution counter. 
In all these trials the outer brass skin of the brake was exposed directly to the 
atmosphere, and consequently the loss of heat by radiation was very large. 
No attempt was made to catch the small quantities of leakage occurring at the 
stuffing-box and the bottom regulating cock. 
The water supply to the stuffing-box was only regulated to the end that the 
bearing should not become unduly hot, and no record was kept of the temperature 
gradient along the shaft till trial No. 10 was reached. 
3 E 2 
