ox THE MECHAXICAL EQUIVALENT OF HEAT. 
419 
Table H. 
Determina¬ 
tion No. 
Trial No. 
W ork. 
Difference of 
work. 
Heat 
(corrected). 
Difference 
of heat. 
K. 
Series No. X. 
XXIV. 
72 
130,522,170 
167,728 
69 
66,154,556 
64,367,614 
84,987 
82,741 
777-9.5 : 
XXV. 
73 
132,158,316 
169,980 
1 
70 
67,130,965 
6.5,027,351 
86,278 
83,702 
776-89 ' 
XXVI. 
74 
133,734,142 
171,921 
71 
68,216,702 
6.5,517,440 
87,757 
84,164 
778-44 1 
Mean value = 777'74. 
XXVII. 
7.5 
132,165,855 
• • 
169,863 
78 
65,732,325 
66,433,530 
84,424 
85,439 
777-56 
XXVIII. 
76 
134,646,463 
17.3,106 
79 
66,358,132 
68,288,331 
85 336 
87,770 
778-03 i 
XXIX. 
77 
135,370,287 
174,071 
80 
67,458,948 
07,911,.339 
86,790 
87,281 
778-07 
Mean value = 777'88. 
1 
Description of the Plates. 
PLATE 3. 
From a pliotograpli in 1888. Is a front view of the triple expansion engines (100 H.-P.) and brakes, 
as thej existed in the engineering laboratory, Owens College, before any modifications for the determi¬ 
nation of the equivalent. The engine-shafts ai’e disconnected from each other, and are working on three 
separate brakes. In the trials the three large pulleys (5 feet in diameter’) were removed with the brakes 
on the high-pressure and intermediate engines, and the engine-shafts coupled by intermedial shafts, the 
work being all absorbed bj' the brake on the low-pressure engine—seen, on the right hand of the jfiate, 
overhanging the last bearing of the brake-shaft. On this shaft are two heavy 3-feet pulleys, which 
served as fly-wheels during the trials. 
It was the facilities afi^orded by this brake and its appurtenances (§ II) that suggested the research 
and rendered it possible: and, although the manner of admitting the water and air to the brake were 
necessarily modified in the experiments, the brake remained essentially the same. Part of the trials 
were made with the brake uncovered, as seen in this plate ; and it was after the brake was covered 
that subsequent photographs were taken. 
The vertical pipe supplying the town’s water from the service tank to the brake, with the hand-cock 
and the automatic inlet-cock above, leading through the bowed pipe and flexible indiarubber tube to 
the inlet passage over the bush of the brake, are seen on the immediate right. Immediately on the left 
3 H 2 
