Magnetic Galvanism. 83 



euabled to trace, distinctly, the galvanic current developed by the 

 magnetic power. 



This simple arrangement furnished a very delicate galvanometer, 

 by placing the spool so as to range,* in length, east and west, and a 

 pocket needle upon the upper part of the coil. Upon connecting it 

 with a small galvanic battery, the ends m and n of the spool became 

 north or south, according to the direction of the current, and the 

 temporary polarity, thus developed, was uniformly so powerful, that 

 the needle, in this form, and in that of the common galvanometer, 

 must be regarded as actually under the influence of a magnet whose 

 poles, being at right angles, occasion the deviation. The current 

 from the magnet is not interrupted by passing through red hot wires. 



Under these circumstances, both sparks and shocks may be readily 

 obtained. 



When the coil on the keeper amounted to one hundred yards in 

 length, the common galvanometer was sufficiently affected by the 

 magnetic apparatus, to furnish definite results, but never indicated a 

 greater declination than ten degrees. The galvanic current is appa- 

 rently directed by that of the induced magnetism of the keeper, the 

 positive one always moving in opposition to the north magnetism. 

 This will account for the following fact. 



When the magnet is stationary, the pulling or sliding off, produces 

 a current opposite to that resulting from the replacement of the keep- 

 er. Hence arises the difficulty of effecting an accumulation of gal- 

 vanic power. Indeed, the difference between galvanism, as gener- 

 ated by the battery, and that developed by the magnet, seems to de- 

 pend less upon intensity, at the commencement, than upon the con- 

 tinuity of impulse and subsequent accumulation. The magnet only 

 produces a momentary effect, and this is succeeded by a counter 

 current, when the keeper is restored. 



The galvanic battery, on the contrary, generates these impulses 

 so rapidly as to create and sustain, in the coil of the galvanometer, 

 a strong magnetic polarity, which occasions the prompt declination 

 of the needle. The battery, moreover, has an equivalent, for want 

 of magnitude, in the increase of chemical action. Hence, the merest 

 metallic points may be made sufficient to cause the needle to fly from 

 its meridian. The action of fused nitrate of ammonia upon zinc is 

 equal to that of the strongest acids, as I particularly noticed in a 

 former communication, and by melting this salt in a platinum cruci- 

 ble, connected with one wire of the galvanometer, I found, that when 



