HISTORY OF GALVANISM. 41 



Ley den phial from the pile; and in this way he 

 was able to demonstrate still more clearly than it 

 had been before done, that the extremity of the 

 apparatus which gives out oxygen is in the posi- 

 tive, and that which gives out hydrogen is in the 

 negative state. 



As the opinion of philosophers was generally Van Ma. 

 agreed in respect to the identity of the galvanic pa? e reTec- 

 and electric influences, many speculations were 

 formed as to what constituted the essential differ- 

 ence between the electric fluid, as generated by the 

 pile, and as disengaged by the common machine. In 

 order to elucidate this point, Van Marum, in con- 

 junction with Professor Pfaff, of Reil, entered 

 upon a series of experiments, in which the action 

 of the pile was compared with that of the great 

 Teylerian machine at Haarlem. He succeeded in 

 charging, not only single jars, but whole batteries, 

 by the pile ; and it appeared that they were 

 always charged to the same degree of intensity 

 with that which the pile itself indicated to an elec- 

 trometer placed upon it. He found that the zinc 

 end of the pile communicated positive electricity 

 to the side of the jar or battery with which it was 

 in contact, and the copper end the reverse. No 

 perceptible difference could be experienced between 

 shocks of the same intensity given by a jar or by 

 the battery ; whether they were charged by the 

 pile or by the machine. He observed that the in- 

 tensity of the pile was always the same from the 

 same number of plates, whatever was their size ; 



