Electro-Magnetic Experiments. 379 



ed. M The neutralizing magnet. S The socket slitted and springy 

 so as to move " finger tight" on T. 



Experiments 1. Having adjusted the magnet to such height as near- 

 ly to neutralize the effect of terrestrial magnetism, I brought the 

 needle to north 45° west and raised a wine-glass of river water to 

 the battery of the instrument, consisting of a five cent piece of silver 

 and a corresponding disc of zinc. The needle turned with an equa- 

 ble velocity to the north, and finally quite to the east having descri- 

 bed an arc of 135° in twenty one seconds. 



2. Having procured a rude piece of antimony and a strip of sheet 

 copper I connected them with the wires of the galvanometer and fi- 

 nally with each other, having previously warmed the copper by hold- 

 ing it in my hands. The needle was deflected 80°. 



3. I applied the two wires to the two extremes of the piece of 

 antimony, which was about three inches long and one a half thick, 

 pressing one wire to it with a piece of wood and the other with my 

 thumb and finger. The warmth of the hand, thus applied caused 

 the needle to turn 76° when the wood and the fingers were changed 

 to the opposite extremes, the needle reversed its motion. 



Whether the above experiments indicate any superior delicacy in 

 the instrument I am not able to say. So far as my own experience 

 goes, it excels by far all other modifications. 



II. Experiments, March 12th, 1834. 



The most delicate experiments which I have made, are as fol- 

 lows : ^^ 



1. When the needle is nearly neutralized by the fixed magnet, 

 the application of river water to the 5 cent piece battery will turn the 

 needle 90° ; and often by impulse throw it entirely round. 



2. The poles (copper wires) of the instrument being held to the 

 extremes of a piece of antimony as large as a hen's egg, the one by 

 a piece of wood and the other by the fingers, the needle will turn 

 90° in consequence of the thermo-electricity generated by the heat 

 of the fingers. 



3. Two discs of copper attached to the poles, and half an inch in 

 diameter including a disc of antimony of the same size caused the 

 needle to turn 90° upon the application of the end of the finger to 

 one of the copper discs. 



Vol. XXVI.— No. 2. 49 



