ELECTRODYNAMIC QUALITIES OF METALS. 
695 
inch, fixed at a distance of 49'8 inches from the mirror. The lamp is placed close 
behind the middle of the scale, and just enough below to allow its light to pass under 
the scale to the mirror through a small blackened tube. The galvanometer used is 
represented in the accompanying sketch (fig. 2). Having been extemporized from a large 
Fig. 2. 
lecture-room instrument, it is not so well adapted for this investigation as I could wish. 
It consists of an astatic pair of needles mounted on a light frame of aluminium, and 
carrying a light mirror placed on the frame, with its centre in the line of the suspension 
a little above the upper needle, and attached by means of clips, so as to admit of its 
being turned into and fixed in any position relatively to the frame. The resistance of 
the galvanometer-coil is ’634 ohm. 
182. On commencing to experiment with this apparatus in March 1874, I imme- 
diately obtained some very startling and interesting results. I found that when a 
current was kept flowing through the magnetizing coil, and weights were alternately 
placed on the pan at the lower end of the wire and taken off, the effect of the pull 
5 d 2 
