202 EF. H. Hali on a New Action of the 
To test this theory, a flat spiral of German silver wire was 
inclosed between two thin disks of hard rubber and the whole 
placed between the poles of an electromagnet in such a posi- 
tion that the lines of magnetic force would pass through the 
spiral at right angles to the current of electricity. 
‘he wire of the spiral was about $ mm. in diameter, and the 
resistance of the spiral was about two ohms. 
The magnet was worked by a battery of twenty Bunsen cells 
joined four in series and five abreast. The strength of the 
justed as to betray a change of about one part in a million in 
the resistance of the spiral, I made from October 7th to October 
11th inclusive, thirteen series of observations, each of forty 
readings. reading was made with the magnet active in a 
certain direction, then a reading with the magnet inactive, then 
one with the magnet active in the direction opposite to the 
first, then with the magnet inactive, and so on till the series of 
forty readings was completed. 
crease of about one part in five millions. : 
Apparently, then, the magnet’s action caused no change 10 
il 
But though conclusive, apparently, in respect to any change 
of resistance, the above experiments are not sufficient to prove 
that a magnet cannot affect an electric current. If electricity 
is assumed to be an incompressible fluid, as some suspect 1t 
e, we may conceive that the current of electricity flowing 1na 
wire cannot be forced into one side of the wire or made to flow 
side of the wire. Reasoning thus, I thought it necessary, 19 
order to make a thorough investigation of the matter, to test 
for a difference of potential between points on opposite sides of 
the conductor. 
This could be done by repeating the experiment formerly 
made by Prof. Rowland, and which was the following: ——, 
- A disk or strip of metal, forming part of an electric circult, 
