GALVANISM. oS[) 



These improvements in the apparatus rendering 

 experiments more easy, gave rise to numerous dis- 

 coveries. It would exceed the limits of this work 

 to detail the history of this science, which is of 

 such modern date. The decomposition of the 

 alcalies and .alcaline earths by Sir II. Davy is a 

 striking proof of the importance of galvanism as 

 a chemical agent. 



The action of all these batteries is greatest 

 when they are first completed, or filled with the 

 fluid ; and it lessens in proportion as the metal is 

 oxydated, or the fluid loses its power. Hence, 

 after a certain time, not only the fluid must be 

 changed, but the metallic pieces must be cleaned 

 by removing the oxydated surface. 



When a galvanic battery consists of tw r enty re- 

 petitions of simple combinations, if you touch with 

 one hand one extremity of the battery, and apply 

 your other hand to the other extremity, you will 

 feel a very slight shock, like that which is commu- 

 nicated by a Leyden phial w r eakly charged ; and 

 it will be hardly felt beyond the fingers, or at most 

 the wrists. This shock is felt as often as you renew 

 the contact. If you continue your hands in con- 

 tact with the extremities, you will perceive a slight 

 but continued irritation ; and when the hand, or 

 the other part of the body which touches the other 

 extremity of the battery, is excoriated or wounded, 

 this sensation is disagreeable, and sometimes very 

 painful. 



The intensity of the charge is, however, so low, 

 that it cannot make its way through the dry skin 

 of the hand, which is but an imperfect conductor: 

 , the fingers should, therefore, be well moistened 

 with water. It will be better to immerse a win- 

 that proceeds from one extremity of the battery in 



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