9G 
L. Sehwendler —On Electric Eight Measurements. March, 
The two electro-magnets, each forming a shunt to the other, are 
adjusted in such a manner, that the extra currents they produce, when the 
primary current varies, are equal, and therefore, as they are invariably 
opposite to each other, they neutralize one another entirely, which will 
have the desired effect of a quicker regulation of the lamp for any varia¬ 
tion of current. 
The iron used in the shunt should have double the weight of the iron 
in the electro-magnet. 
The section of the wire for filling the shunt should be double the 
section of the wire filling the electro-magnet. 
Coil on so many convolutions on to the shunt until its resistance 
becomes equal to the resistance of the electro-magnet. 
For adjusting the equality of the extra currents the following method 
should be adopted :— 
Form a Wheatstone bridge two sides of which are formed by a 
mercury-rheostat, each side offering about 002 S.U. resistance. The 
third side of the bridge is formed by the electro-magnet of the lamp, the 
fourth side by the shunt. In one diagonal place a dynamo-electric 
machine and about one unit resistance, together with a convenient make- 
and-break contact, best done by a mercury cup. In the other diagonal, 
place a Bell-telephone, of lowest possible resistance. One end of this 
diagonal can bo moved along the mercury-rheostat. Start the dynamo- 
electric machine, listen to the telephone and alter the ratio of the 
mercury-branches of the bridge, by shifting along the contact until the 
telephone is perfectly silent. 
I hen if, at commencing and stopping the current a strong click is 
heard, we know it is due to the two extra currents not being equal, and as 
we further know that the shunt produces the greatest extra current, we 
make this extra current smaller, by shifting along the two poles of’the 
shunt, an iron wedge until the telephone is quiet, when starting and 
stopping the current. The iron wedge is then fixed in its position. 
This shunt is also to be inside the metal cover of the lamp. 
7. The two terminals of the lamp are to be of exactly the same 
pattern and size as those used in the dynamo-electric machine described 
in the commencement of this Appendix. 
They must not be terminals with hand screws. 
APPENDIX III. 
On some of tiie Scientific Results obtained by 
Experiment. 
System of Units adopted In my investigations I have adopted 
the Centimetre- Gramme-Second system of units. 
