on a Permanent Electric Current. 163 
enters and leaves the metal strip by means of the binding 
screws e, e. Running out from the middle of this strip are two 
projections which make contact with the clamps C,, C,, worke 
by the screws S, S,. From the screws 7, 7, wires lead to the 
Thomson galvanometer. The projections from the metal strip 
just alluded to make the apparatus very easy to adjust, for by 
scraping off little particles from the proper part of the projec- 
tions, while the current is allowed to run through the metal 
strip, the current through the Thomson galvanometer may be 
reduced to the extent desired. 
In ordinary experiments such a plate as that just described 
is placed between the poles of the magnet in such a position 
that the direction of magnetic force would be represented by a 
perpendicular to the plane of the paper in the above drawing. 
In the variation upon the main experiment a plate was em- 
ployed similar to the above, but narrower and with very short 
side clamps. This plate was first placed between the poles of 
wiecnes a in the usual position as shown by the heavy lines 
in fig. 2. 
With this arrangement a permanent deflection of about 30° 
cm. on the scale before the Thomson galvanometer could be 
obtained by reversal of the magnet current. Leaving now the 
distance between the poles very nearly the same as before and 
using, both in the magnet and the gold strip, as nearly as 
possible the same strength of current which had just been em- 
ployed in the previous trial, the plate was turned into the 
position indicated by the dotted lines in fig. 2. With this — 
second arrangement no action of the kind previously seen was 
detected, or at least none that could with certainty be distin- 
guished from the direct action of the magnet on the Thomson 
