86 



Magnetic Galvanism. 



power of holding magnetism depends upon its being undisturbed, and 

 we may, at any time, remove it all, by simply pressing the wire so as 

 to bend it gently backwards and forwards at its center. Upon test- 

 ing this instrument with a galvanic battery, I found that it was not so 

 delicate as the common one when the bath consists of pump water 

 or weak saline solutions, but its value in pointing out the galvanic 

 currents, generated by the magnet, is not diminished by this circum- 

 stance, since the common galvanometer is scarcely affected, and, it 

 the coil upon the keeper be the cause of this defect, it is highly prob- 

 able that extending it will not add to its power over the needle. 



The magnetic apparatus occasions prompt declination of 'the nee- 

 dle, by the assistance of this wire, where the ends of the conductors 

 are separated from each other eighteen inches, and plunged into acid- 

 ulated water. If such strong magnetism can be impressed upon soft 

 iron by this arrangement, it is obvious that a galvanometer of infinite 

 delicacy might be constructed by bending fine iron wire, closely 

 bound by a continuous coil, into the form of the coils in the common 

 galvanometer, and increasing their number. This mode would also, 

 I think, furnish the most powerful temporary magnetism by givin 



or 



fi 



spective coils, so as to make the whole continuous, and bound the 

 wires firmly together to grind down their ends until they formed 

 smooth polar surfaces. 



