HISTORY OF GALVANISM. 93 



its wonderful effects are accomplished, Mr. Child- 

 ren was advantageously employing himself in im- 

 proving the apparatus. He formed a battery, PLATE t 

 constructed upon the principle employed by Volta, ls ' 

 in the couronne des tasses, according to which the 

 plates are not in contact through the whole of 

 their extent, but are connected only at the top by 

 a metallic conductor, and are then immersed in 

 the cells of a trough. He employed 20 pair of 

 plates, of four feet by two, making in all a sur- 

 face of 92,160 square inches. The fluid that he 

 used was a diluted mixture of nitric and sulphuric 

 acids, the whole quantity being no less than 120 

 gallons. The effect of these large plates was to fuse 

 entirely, in about 20 seconds, 1 8 inches of platina , / 



wire, of one-thirtieth of an inch in diameter, and 

 to render three feet of the same wire red-hot. 

 Charcoal burned with intense brilliancy. It 

 seemed not a little remarkable, considering the 

 powerful effect on platina wires, that the action of 

 this battery on iron wires was comparatively trifling. 

 Of iron wire, one-seventieth of an inch in diameter, 

 it barely fused ten inches, and was not able to ignite 

 three feet. It had not the power of decomposing 

 barytes and other similar substances ; it did not 

 affect Bennet's electrometer ; and it scarcely pro- 

 duced a perceptible shock. 



Mr. Children next formed a battery of 200 pairs c om para- 

 of plates of two inches square, affording a surface 

 of 3,200 inches. With this the alkalies and alka- P lates - 

 line earths were readily decomposed, and a con- 



