478 Brackett and Young—Edison’s Dynamometer, 
During the experiment the electromotive force of the current 
by which the field magnets were maintained was only 6-26 
volts, consequently the machine was not giving nearly its max- 
imum current—the energy expended being about 6:25 horse- 
power and the current about 46 webers. 
During the next test, which continued nine minutes, the elec- 
tromotive force of the field coils was maintained at 14°9 volts, 
and the current produced was 57°5 webers—consuming 9° 
horse 
The calorimeter was refilled with fresh water; and proceed- 
ing as before we found— 
Energy measured by dynamometer -... 2,827,550 ft. lbs. 
Energy expended on field.._...-.----- 72,180 7% 
Total tienda} nko 2sBORe0-- 7 
Energy realized in calorimeter. --. --. - 2,259,700 ft. Ibs. . 
Energy realized in leading wires - ----- | BR oT? 
Energy realized in armature........-. 183,930 “ 
TOMES. ei eet Ras E es eS 
Avyeuaie 5405222. 2,267,238 “ 
meee GOIONOY 2 er 84°5 per cent. 
Available efficiency -._-...........-- mere Lt es 
These results were confirmed by the reading of the high re- 
sistance galvanometer. 
Tabulating our results they stand thus: 
Total efficiency. Available efficiency. 
Ist 82°3 per ct. 78°7 per ct. 
2d 84°6 “cc 78-2 “cc 
8d 84°6 “ 78-9 “ 
Mean , 83°8 “ 8-4 “c 
If we assume that the indications of the Prony dynamometer 
are reliable and that the loss in transmitting power between the 
idison dynamometer and the arbor of the armature was only 
the same as the loss between the two dynamometers, the above 
numbers will have to be increased inthe ratio of 100 to 932, 
and we shall have— 
Total effictenty = 25.2 2725 AA 89°9 per cent. 
Available efficiency . 2.22.22) 2/2:2-- ig ie 
These figures we believe fairly represent the performance of 
the machine in its present conditi 
As points of excellence in the construction of this machine, 
.we may mention the employment of large masses of iron 10F 
the field magnets; the breaking up of the armature core into 
thin plates, thus avoiding the expenditure of much useless 
