191 
APPENDIX. 
Calculations, according to Joule’s present theory, for his 
experiments in 1845. 
N.B. The calculations are only close approximations, and 
not perfectly accurate. 
FIRST EXPERIMENT. 
I. When the engine was at rest, current in BA units, 
1,296. 
1. Heat evolved per hour by the wire = 102-89 units. 
2. Consumption of zinc per hour, 49 7 ’7 grains. 
3. Heat clue to 497 '7 grains, 102*89 units. 
4. Work per hour (102-89 - 102-89)772 = 0. 
5. Work per grain of zinc = 0. 
II. The engine was then started, and kept to a velocity 
which reduced the current to -5338. 
• 5338 \ 2 
(? 
296 / 
= 1715 
1. Heat evolved per hour by the wire, 102-89 x 
units. 
2. Consumption of zinc per hour, 497*7 x JIM? = about 205 
1'296 
grains. 
3. Heat due to 205 grains, 102-89 x = 42-25 units. 
4. Work per hour (42 - 25 - 17-15) x 772 = 19.377 ft. lbs. 
SECOND EXPERIMENT. 
III. The current is reduced to *495. 
1. Heat evolved per hour by the wire, 102-89 x =15-15. 
2. Consumption of zinc per hour, 49-77 x = about 190 
grains. 
3. Heat due to 190 grains, 102-89 x = 39-28. 
-L zyb 
4. Work per hour (39'28 - 15-15) x 772 = 18,628 ft. lbs. 
THIRD EXPERIMENT. 
IV. When the engine was at rest, current *806. 
1. Heat evolved per hour, 63 -88 units. 
2. Consumption of zinc per hour, 309 grains. 
3. Heat due to 309 grains, 63-88 units. 
4. Work, 0. 
