86 



Mr. H. Wilde's Experimental Researches 



taming what influence the number of magnets on the cylinder 

 had upon the quantity of electricity generated by the machine, 

 as indicated by the galvanometer. 



19. During these investigations, the armature of this machine 

 was driven by steam-power at a constant velocity <>£ three 

 thousand revolutions (equivalent to six thousand, waves of elec- 

 tricity [141) per minute. The direct current from the machine 

 (15) was transmitted through one of Pouillet's galvanometers 

 of tangents, constructed by Ruhmkorff, which was placed be- 

 yond the influence of the magnetism of the machine. The re- 

 sistance 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. 



Number of magnets 

 on cylinder. 



Deviations of 

 galvanometer. 



Tangents of 

 deviations. 



1 

 2 

 3 

 4 



29-25 

 52-00 

 62-75 

 67-75 



0-56 

 1-28 

 1-94 

 2-44 



21. In making these experiments, which have often been re- 

 peated 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 de- 

 ficiency 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 composed. 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. 



