1819.] History and Present State of Galvanism. 135 



ies nerfs ne seroient que des tuyaux, dont tout l'effet dependroit 

 de la liqueur qu'ils contiennent." 



After giving a concise account of Galvani's experiments and 

 speculations, our author notices the publications of Valli and 

 Fowler, the paper of Dr. Wells, the experiments of Humboldt, 

 the letters and theories of Volta, and the paper of Fabroni, of 

 Florence. Galvani ascribed the phenomena to the nervous 

 fluid, Volta to common electricity, and Fabroni to the chemical 

 action of the substances employed upon each other. 



2. Volta ascribed the galvanic phenomena to the electrical 

 action of the two metals upon each other. Bennet and Cavallo 

 had shown that certain metals, when placed in contact, and then 

 separated from each other, are found in different states of electri- 

 city ; the one plus, and the other minus. Volta conceived that 

 the evolution of electricity in galvanic experiments was owing 

 to this law. The zinc plate became plus, and the silver or 

 copper plate minus. He conceived that by increasing the 

 number of plates with a liquid conductor between each pair, the 

 electricity might be increased at pleasure, and the effects 

 accordingly made as conspicuous as could be desired. This 

 fortunate idea gave rise to the Voltaic pile, which was found by 

 the inventor capable of giving shocks, and of producing more 

 violent convulsions than a single pair of plates could do. 



Volta's description of the galvanic pile was published in the 

 Phil. Trans, for 1800. Messrs. Nicholson and Carlisle were 

 the first to try the properties of this new instrument. Ihey 

 speedily discovered that it possessed the power of decomposing 

 water, that the oxygen was evolved from the wire attached to 

 the zinc end of the pile, which they found to be the positive 

 wire ; while the hydrogen was evolved from the wire attached 

 to the copper end of the pile, or the negative wire. 



Mr. Cruickshanks, of Woolwich, substituted the trough for the 

 original pile of Volta. This was found a much more convenient 

 modification of the apparatus than the original contrivance of 

 Volta. It has, therefore, taken its place, and been gradually 

 improved into the state in which it is at present employed. 

 Cruickshanks observed several of the decompositions produced 

 by the Voltaic trough, and ascertained the laws of these decom- 



Eositions. These decompositions were carried still further by 

 [enry, and particularly by Davy. 



Cruickshanks observed that liquids destitute of oxygen are 

 incapable of transmitting the galvanic energy, while it is trans- 

 mitted in his opinion by every liquid that contains that 

 principle. Col. Haldane found that the apparatus ceased 

 to act when plunged in water, or when placed in the vacuum of 

 an air-pump. Azotic gas had the same effect as a vacuum ; 

 while oxygen gas made it act more powerfully. From these 

 facts, and from a series of experiments by Dr. Wollaston, it was 



