CHAP. III. 



GALVANOMETER. PEEOAUTIONS TO BE OBSERVED. 



It wiU not be necessary for me to enter into the 

 subject of the construction of the galvanometer, or of 

 the principles of its action; but merely to observe, that 

 for the purpose of electro-chemical research, a gal- 

 vanometer consisting of several coils of thin wire 

 wiU be found to be the most appropriate ; whilst for 

 the study of thermo-electric and of magneto-electric 

 researches, a galvanometer consisting of a few coils 

 of thick wire or of a plate of copper will be found to 

 be the best. For our present purpose, the former 

 with several coils will be found the most applicable ; 

 at the same time we must not overlook the import- 

 ance of occasionally using the latter. 



The mode usually adopted, and found mos 

 convenient to pursue in these experiments, was as 

 follows. The galvanometer was placed and well 

 secured on a firm table or stand, free from any 

 vibrations of the room, and with a good light falling 

 upon it, at the same time not exposed to the direct 

 rays of the sun, so as to avoid the production of 

 air-currents within the shade of the instrument. 

 Two thick copper wires, about six inches in length, 

 were bent at right angles, so that one extremity 

 should be attached to the instrument by means of 



