( 109") 
: : : P Wet 
arrives at, differs from formula (1), in having —— instead of C, h 
w 
being an instrumental constant. 
According to HERMANN formula (1) must be: 4) , 
dy h 
aye) are PT Je 
dT w (9) 
This formula represents the facts in so far as the increment of 
nine . | a 
the resistance varies directly as the increment of “er accordance 
with what I have said in a former paper and as will be discussed 
further on. This is occasioned by the fact, that the mechanical 
friction in the capillary has a similar influence on the motion of 
the mercury as the ohmic resistance in the circuit. HERMANN 
: 1 
wrongly concludes that the constant must be proportional to — 
w 
whereas from the experiments is to be inferred only, that it is pro- 
) 
1 
portional to phe Differently stated HERMANN wrongly assumes 
a W 
that a= 0, 
The error of his formula is to be ascribed to a misconception of 
the action of the capillary electrometer. 
He neglects entirely the influence of the mechanical friction in 
the capillary on the motion of the meniscus, whereas this mecha- 
nical friction is with most capillary electrometers of the foremost 
importance. This may be inferred from the following. 
Using capillary G 103 and suddenly applying a P. D. remaining 
constant, a normal curve was described, no additional resistance 
being inserted in the circuit. This curve was measured and the con- 
stant, which we will call C.*), determined according to formula (1). 
Then a normal curve was taken with the same instrument, a resistance 
of 0,1 Megohm now being inserted in the circuit, and the value of 
the constant, now indicated by C,, was determined again. 
1) Hermann’s formula in his own symbols is: 
oy hy 
Lm (kH—y); 
sf = 9); 
k E being here identical with y* of formula (1). 
2) The manner in which the constant C is caloulated from the normal curve was 
given formerly, vid, Prrücer’s Arch, 1. c, 
