On the Excitement of Voltaic Plates. 171 



ttuce an effect equal to ojie contact and separation of M. Volta's 

 plates, and an effect very far inferior to one contact and separa- 

 tion of mv plates, to which they exactly correspond in size? 

 Some extraneous cause must, indeed, have operated in the ex- 

 periments of i\I. Haiiy and of Mr. De Luc. Probably their elec- 

 'rometers uere not very delicate; possibly they did not pay due 

 regard to tliose circumstances on which depends the full action of 

 vhe plates. 



In reference to the production of Galvanism, I also observed 

 tiiat the Galvanic apparatus can only be excited by a decom- 

 posable fluid. This 1 meant to be equally applicable to the pile 

 and the trough: — it is a fact which has been generally believed, 

 but which Mr. De Luc thinks he has demonstrated to be false. 

 Witii due deference to him, the following appear to be conclu- 

 sions fairly deducible from his analysis of the pile, in reference 

 to this subject. 



1. The necessary combination for the greatest excitement, 

 consists of two dissimilar metals with a moist substance inter- 

 posed between them. 



2. If this condition be" observed, although no two metallic 

 surfaces be in contact, but merely connected by conducting 

 points, as in the first dissection, the effects will be the same, or 

 nearly the same, as if the pile had not been dissected, but had 

 remained continuous, in which state the different metallic sur- 

 faces are in contact. 



3. If the pile be so dissected that two metallic surfaces be in 

 rontact, but the moist substance in contact with only one of 



iiem, if that one be the most oxidable metal, the powers of the 

 iie will only be diminished; but if the metal in contact with 

 :.e moist substance be the least oxidable, then will the power of 

 .e pile entirely cease. 



4. A solution of sea salt is capable of exciting more power- 

 lly than common water. The same pile which when excited l)y 

 ater was only capable of aifecting tiie electrometer and pro- 

 icing decomposition, when excited by a solution of muriate of 



■ )da affected the electrometer, occasioned decomposition, and 

 iforded a shock. 



5. The power of vegetable and animal substances to produce 

 a-itement is, cceteris paribus, \\\ propoition to \.\\e.\v moisture \ 



pile excited bv new cloth, wliich had stood some time in a 



-om in which the hygrnmcter was at 4()', l;eing only capable 



r" affecting tlie electrometer, while the same pile excited by wet 



oth affected the electrometer and produced decomposition"*'. 



Mr. De Luc, in spite of these natural inferences from his own 



* Sec Aiuilysi's ol" the Galvanic I'ilc. 



experiment.'*. 



