IN magnetism and electricity. 
93 
waves of electricity) (14) per minute. The direct current from the machine (15) was 
transmitted through one of Pouillet’s galvanometers of tangents, constructed by 
Ruhmkoref, which was placed beyond the influence of the magnetism of the machine. 
The resistance of the galvanometer coils was so small in proportion to the resistances of 
the other circuits employed in these researches, as to render it unnecessary to take it 
into account. 
20. Four permanent magnets (12) were placed successively upon the magnet-cylinder 
at a distance of half an inch from one another, and as each additional magnet was placed 
upon the cylinder, the deviation of the galvanometer-needle was read off after it had 
taken up a steady position. The results of these experiments are shown in the following 
Table. 
Table I. 
No. of magnets on cylinder. 
Deviations of galvanometer. 
Tangents of deviations. 
1 
29*25 
0-56 
2 
52-00 
1-28 
3 
62*75 
1*94 
4 
67*75 
2-44 
21. In making these experiments, which have often been repeated at different times, 
it was invariably found that, when only one magnet was on the cylinder, the quantity of 
electricity generated by the machine was proportionately less than when two or more 
magnets were placed on the cylinder. This deficiency appears to me to be due to the 
small amount of magnetism of a single magnet having to diffuse its influence through 
the comparatively large masses of iron of which the cylinder and armature were com- 
posed. After making allowance for this discrepancy, together with errors of observation, 
it will be seen from an inspection of the above Table, that, within the limits of these 
experiments, the quantity of electricity generated in the wire surrounding the armature 
of the magneto-electric machine is in direct proportion to the number of magnets on 
the magnet-cylinder, or to the quantity of magnetism induced in it. 
22. A second series of experiments was made with the view of ascertaining the relation 
existing between the lifting-power of the permanent magnets on the magnet-cylinder, 
and that of an electro-magnet excited by the electricity derived from the magneto-electric 
machine. In these investigations the apparatus shown in fig. 8 was used, which con- 
sisted of a small electro-magnet, made by bolting to an iron block, forming the base of 
the electro-magnet, two plates of iron 6 inches long, 3 inches wide, and f-ths of an inch 
thick. The inside distance between the two plates was about 2 inches ; and the polar 
surfaces of the magnet were truly planed, as was also the under surface of the keeper or 
submagnet used in connexion with it. This submagnet was made of a small block of 
iron about 3 inches square and 1 inch in thickness, and was connected, by means of a 
link and swivel, to one end of a scale-beam supported at its centre by an upright pillar. 
From the other end of the beam depended a scale-pan, which was weighted so as to 
