358 
DRS. J. AND E. HOPKINSON ON DYNAMO-ELECTRIC MACHINERY. 
terminals of generator ; column VI., amperes in external circuit ; column VII., 
rheostat resistance ; column VIII., watts in generator armature ; column IX., watts 
in motor armature; column X., watts in generator shunt magnet coils; column XI., 
watts in motor shunt; column XII., watts in generator series magnet coils; column 
XIII., watts in motor series; column XIV., watts in external resistances; column 
XV., total electrical power of generator; column XVI., half the sum of losses un¬ 
accounted for; column XVII., total mechanical power applied to generator. 
Table IV. gives the losses and efficiencies as percentages in exactly the same way as 
in Table II., excepting that another column is introduced for the loss in the series 
coils of the magnets of the generator. 
The core of the armature contains about 6500 cub. cms. of iron. Hence energy 
of magnetising and demagnetising when the speed =1100 revolutions per minute 
= 6500X“^-X 13,356 in ergs per second = 159 watts.] 
In conclusion we desire to express our indebtedness to Messrs. Mather and Platt, 
by whom the machines we have used were manufactured, and who, in placing the 
same at our disposal, together with all facilities for carrying out our experiments at 
their Salford Iron Works, have enabled us to put theory to the test of experiment on 
an engineering scale. 
