of Edinburgh, Session 1874 - 75 . 555 
G-rotrian used it in testing the validity of their method.* That, 
however, Professor Beetz’ method is free from all the disturbing 
effects of electrolytic action seems not yet to be thoroughly estab- 
lished. Du Bois-Reymond’s experiments show that there is no 
polarisation. But do Professor Beetz’ experiments! prove that 
new compounds are not formed by the passage of the current, of 
different conductivity from that of the original liquid? In the 
tube which contained the electrolyte he placed several pieces of 
amalgamated zinc, which fitted the tube closely like pistons 
Holes were bored through the axis to enable liquid to pass from 
one side to the other. Generally, he says, the pieces of zinc, so 
soon as they touched, clung fast to one another ( [hafteten fest an 
einander ), but they could always be separated by inclination of the 
tube. When all the pieces were lying close together, and one of 
them close to a zinc electrode, the current would have to pass only 
once through the electrolyte ; but when they were separated from 
one another, it must several times pass through the solution. If 
any new resistance were produced there would be several times as 
much produced in the second as in the first case, and the fact 
could be observed. This would be conclusive, if it was certain 
that there was contact between the pieces of zinc lying next one 
another. If the amalgamated surfaces had been coated with liquid 
amalgam, there would be sufficient certainty of contact to warrant 
trust in the experiment. But that does not seem to have been 
the case, as Professor Beetz does not mention it, and therefore 
leaves bis readers free to suppose that he did not rely upon its 
agency. He must then have taken for granted that, without the 
use of any pressure, the pieces of zinc could be brought so close 
together as to prevent the liquid from penetrating between them, 
— a somewhat doubtful supposition. If there was a layer of 
electrolyte, however thin, between each two neighbouring pieces 
of zinc, electrolysis would occur at as many points of the tube as 
when the zinc pieces were farther separated, and the resistances 
observed would be equal whether compounds of greater or less 
resistance were formed or not. Hence, until more is known of 
the mode in which Professor Beetz assured himself of the contact 
* Pogg. Ann. cliv. p. 9. 
VOL. vm. 
t Ibid, cxvii. pp. 6-8. 
4 c 
