220 SCIENTIFIC RECREATIONS. 



which he denominated " Couronne des tasses" (fig. 220). It consisted of a 

 series of small glasses containing water or asaline solution. He then procured 

 a number of " metallic arcs," partly composed of zinc and partly of copper ; 

 these were inserted into the glasses, so that every glass contained -the zinc 

 of one and the copper of another arc, not in contact, but one at the right 

 hand the other at the left. The electro motion, supposed to be the primary 

 cause of the galvanic action, was thus produced as well as from the " pile." 

 The principle was just the same in both apparatus, the metals being divided 

 by the water in one case, and by a wet card or cloth in the other. 



Volta, in 1800, addressed to the Royal Society his celebrated letter 

 upon electricity excited by contact of conducting substances, and then the 

 English philosophers proceeded to make further experiments. It was Fabroni 

 of Florence who had just before suggested that chemical action was really 

 the cause of the phenomena exhibited. Sir Humphrey Davy warmly 

 advocated this theory, and made numerous experiments with the view to 

 establish it. Nicholson, Carlisle, and Cruickshank also paid great attention 

 to the subject. Volta, although he had laid the foundation, did not venture 



Fig. 220. Volta's couronne des tasses. 



to build upon it. Messrs. Nicholson and Carlisle found the two kinds of 

 electricity in the pile, the zinc being positive and the silver negative. They 

 also found that the water was decomposed both in the circuit and in the body 

 of the pile. Subsequently Cruickshank confirmed Nicholson's observations,, 

 and made use of what is termed the " trough " apparatus. He found that 

 hydrogen was emitted from the silver or upper end, and oxygen from the other. 



These discoveries opened up a wide field. " The power of the pile in 

 decomposing chemical substances was now established." Dr. Henry 

 employed galvanism for analysis, and Sir Humphrey Davy invented new 

 combinations of substances. He formed a pile of charcoal and zinc, and 

 found out that a pile could consist of only one metal, different fluids being 

 applied to the opposite surfaces separated by water, and one fluid " capable 

 of oxidating the metal, the other of preventing the effect of oxidation." Soon 

 after a pile was made of charcoal. 



In 1 806, Sir H. Davy gave the results of his researches to the world 

 upon the electro-chemical action of bodies. In the course of his experiments 

 he found out the chemical constituents of the alkalies, and a surprising 

 number of new things were brought to light, and chemical science received 

 a most astonishing ally. Sir W. S. Harris says : " A series of new substances 



