GALVANISM. 885 



This machine will continue in action a very long 

 time, and when the pieces of zinc are oxydated 

 they may be easily taken out and cleaned. 



Volta chiefly confined his experiments with gal- 

 vanism to its effects on animals. He considered it 

 to be the same as electricity, because it gave a 

 similar shock ; and because, having applied two 

 rods, one formed of silver and the other of tin, to 

 the two disks of Nicholson's doubler, he found that 

 the disk in contact with the silver rod indicated 

 negative electricity, and that in contact with the 

 tin showed positive electricity. These experi- 

 ments were repeated in this country by Nicholson 

 and Carlisle ; and, in the course of them a part of 

 the circuit of the pile happening to be formed 

 through water, they noticed the decomposition of 

 that fluid, as shown by the separation of the two 

 gases of which it consists. 



The apparatus for showing this is extremely 

 simple. Fill a small glass tube with distilled water, 

 and fitting a cork to each extremity, as in Fig. 14., 

 make a piece of brass or copper wire pass through 

 each of the corks into the water. Connect then 

 the wire A with one of the extremities of the bat- 

 tery, while the wire B communicates with the other 

 extremity. You will then find, that minute bubbles 

 of gas proceed in a constant stream from the end 

 of the wire, which passes from the negative end of 

 the battery, and ascending to the upper part of the 

 tube accumulate by degrees. This gas, if examined, 

 will be found to be hydrogen, and may be inflamed 

 by the approach of an ignited body on pulling out 

 the cork. At the same time the other wire depo- 

 sits a stream of oxyde in the form of a cloud, which 

 gradually accumulates on the sides and bottom of 

 the tube. If you interrupt the circuit, the streams 



vol. i. c c 



