48 TRANSITION RESISTANCE——MACGREGOR. 
whose parts had the same aggregate resistance that in the one 
there was a single passage from one metal to another, in the other 
several such passages, and finding that the resistances of the two 
circuits were the same. 
In the case of electrolytes there may be not only the form 
of transition resistance mentioned above, but also another aris- 
ing from the chemical decomposition which the current effects. 
Even when no solid or liquid substances are deposited on the 
electrodes and no gas is given off from them, there is usually 
some change produced by the current in the surfaces of the elec- 
trodes, for they are usually polarised. It is possible therefore 
that the very process of electrolysis may give rise to such a state 
of the surfaces of the electrodes that the current is weakened 
in passing across them. 
These two possible forms of transition resistance are usually 
spoken of together under the one name, there being no experi- 
mental means of separating them. The determination of their 
existence or non-existence is rendered difficult by the fact, that 
the passage of the current through an electrolyte modifies the 
resistance of the electrolyte by changing its constitution, and 
changes the electromotive force of the circuit by producing 
polarisation. 
Lenzt and PoagenporFr* thought to eliminate polarisation 
by the use of rapidly alternating magneto-electric currents ; and 
the latter, basing on this assumption, not only regarded the ex- 
istence of a transition resistance proven, but made an investigation 
of its laws. VORSSELMAN DE HEER,} however, has pointed out 
that this assumption is not only unwarranted but shown by ex- 
periment to be inaccurate. I have arrived at the same result 
in some experiments made to test the method which KoHL- 
RAUSCH and NippoLpT used to measure the resistance of elec- 
trolytes. Although I made 250 currents per second pass through 
various saline solutions from a magneto-electrie machine which 
was made to work with great regularity, yet a sensitive galvan- 

+Pogg. Ann. XLVII (1839). 
* Pogg. Ann. LIT (1841). 
+ Pogg. Ann. LIII (1841). 
