VOLTAIC ELECTRICITY. 53 



Magnetism, and Electricity ;" to which excellent work the reader 

 is referred for these and a variety of other interesting phenomena. 



In the powerfully-energetic action consequent on the intro- 

 duction and direct contact of two distinct metals in acidulous 

 media, and the quiescent state to which these operations are re- 

 duced by the sudden separation of contact of such metals, would 

 rather support the theory that the polar arrangements, as to 

 their molicular combination, are various and distinct in every 

 species of metal ; and that such difference of constitution, influ- 

 encing their crystalline form, indicates their compound nature. 



The precipitation of metals from their acid solutions by the 

 introduction of some other metal, such as copper by iron, lead 

 by zinc, as in the instance of the lead or philosophical tree, and 

 silver by mercury, as in the case of the arbor Dianee, exhibiting 

 as they do most beautiful arborescent formations, are instances 

 of the electro-galvanic action ; and the assumption of such 

 forms are perfectly analogous with the operation of the same 

 force in the formation of organized bodies in the vegetable 

 kingdom. 



In the elaborate researches of Professor Faraday, conducted 

 with his usual accuracy and precision, on the interesting subject 

 of electro-chemical decomposition, he has drawn inferences from 

 a number of experimental results, by which he has established 

 from a series of facts some laws of electro-chemical action of 

 high importance. 



It may be as well to remark that the learned Professor has 

 adopted terms at once appropriate and expressive of their nature, 

 and derived from the Greek. For the term pole he uses that of 

 electrode as a substitute ; and to convey the idea of the point at 

 w T hich the current of electricity is considered to enter the 

 decomposing body, as parallel to that supposed to exist in the 

 earth, he calls the negative extremity the anode, where oxygen, 

 chlorides, acids, &c. are evolved, and is against or opposite the 

 positive electrode ; while he uses the word cathode to express 

 that surface at which the current leaves the decomposing body, 



