14. W. N. Milli—Electro-Dynamometer for Large Currents. 
The weight employed exactly balances the magnetic force. 
The mode of observing the zero point was not quite. satisfac- 
tory. It was originally intended to use a vertical wire stop, 
the pointer-rod to be drawn back until it just touched the wire, 
but it was found that it was difficult to hit this point exactly. 
Finally, a scale was marked on the cylinder in front of the 
instrument (fig. 1) and a pointer of aluminum wire fastened 
to the rod, so that it would traverse the scale. This plan 
worked well and with more carefal construction will Ted ty 
be sufficient, but a better method is probably one suggested 
Captain F. M. Ramsay, U.S. N., which is to use a light ane 
cal pointer hanging over the scale on the base. When ad- 
justed, the pointer-rod of the suspended coil Boule just one 
the vertical pointer when the latter is at z exact 
return to the same point would be easily Patt as a eal excess 
of weight would cause a movement of the pointer over the 
scale, 
The pans are of the same weight and the threads by which 
they are hung, are fibers of unspun silk. The friction of the 
pulleys is very small, and would be trifling if they were made 
were aimed at. Tt must be vasieisbenes that the actual obser- 
vation is made when the coil is in the zero aking the weight 
taken being that required to balance the deflecting force. The 
movement of the pulleys is then very slight and the weight acts 
exactly at right angles to the pointer-rod. 
For the measurement of the large currents derived from dy- 
namo-electric machines, minuteness is not demanded, since the 
. due to fluctuations in cage currents, alterations. in 
measuring currents of ion 20 to 80 webers. It isa good work- 
ing instrument and gives uniform results. It eg made for 
seal trial and is defective in certain respects. With 
so mprovements in construction, it would be a little more 
sensitive careculaely to comparatively small currents. The 
