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HISTORY OF SCIENCE. 



powerful than when only water was used ; but he attributes this to 

 the better conducting power of such solutions. Seeking to remedy 

 the rapid diminution of the power of the pile, which he attributed 

 to the drying up of the moisture in his porous discs, Volta was led 

 to the happy modification of the apparatus that received the name of 

 the " Crown of Cups " (couronne detasses). This is represented in Fig. 

 265, where the saline solution is seen to be contained in distinct 

 vessels, into each of which is plunged a plate of zinc, z, and a plate of 

 copper, K, and the copper in one vessel is connected by a wire with 

 the zinc in the next vessel, and so on throughout. The meaning of the 

 arrows placed over the wires will be explained in the sequel. 



FIG. 265. THE "CROWN OF CUPS." 



Volta failed to study, or at least he passes over in silence, the 

 chemical changes, which are sufficiently obvious in one of the arrange- 

 ments just described. The corrosion and solution of the zinc by the 

 acid or saline solution were probably regarded by himself as accidental 

 effects in no way related to the development of the electricity, and 

 the prepossession of his mind by the contact theory would indispose 

 him to look any further into the matter. Now, the discovery an- 

 nounced in the first instalment of Volta's letter having been privately 

 communicated by Sir Joseph Banks, the President of the Royal So- 

 ciety, to several of the members before the complete communication 

 was received, experiments were instituted in London to confirm and 

 elucidate Volta's results. Thus it happened that the chemical powers 

 of the pile were discovered by Carlisle and Nicholson on the 2nd of 

 May, 1800. They were endeavouring to find the nature, positive or 

 negative, of the electricity at the ends of the voltaic pile they had con- 

 structed with half-crowns and discs of zinc, and in placing the end of 

 a wire in a drop of water to obtairr better contact, they noticed that 

 the wire became covered with minute bubbles of gas. This led to 

 further investigations, and the two experimenters were soon able to 

 announce that they had succeeded in decomposing water by the 

 agency of Volta's pile. The decomposition of water by electricity, 

 an experiment which soon became classic, is described in another 

 chapter. By July in the same year, 1800, William Cruikshank had 



