2 70 Bulletin of Laboratories of Denison University [Voi. xi 
and friction is reduced. It is also much more readily cleaned 
than the other, if occasion should arise. Further, it is much 
more difficult to blow an instrument of Ostwald’s second form, 
if the capillary is smaller than .5 mm. But the modified 
Paschen type is readily made with a capillary as small as . 2 mm. 
with a gain in sensitiveness about six fold. 
Comparing the best of the latter type with about ten 
electrometers of Ostwald’s third form, I found it three times as 
sensitive as the best of them. It was exceeded in sensitiveness, 
it is true, by one of them but this one maintained a useful life 
only one hour long. A partial determination of its sensitive- 
ness was hardly completed when it suddenly stuck. Two days 
were wasted in an unsuccessful attempt to wash, dry and refill 
its capillary. The mercury could not be again forced through 
it. Its diahieter did not much exceed .01 mm. (as against .21 
in the Paschen). Such experiences with very sensitive elec- 
trometers of the Ostwald third type are not uncommon. The 
larger capillary in the other instrument prevents this difficulty. 
Figure 5 shows the construction of the modified Paschen 
form, as exhibited by the instrument before referred to as 
“No. 6.” The letters a, b, c, etc., designate the .^^ame parts 
as in the other figures. To give an idea of the dimensions the 
following will suffice: Internal diameter of capillary ^ .21 mm., 
of tube <^8.2 mm., of the outer containing tube 16 mm. The 
mercury stands 39 mm. higher in b than in a. The capillary 
a is drawn down from a thick walled capillary of 2 mm. inter- 
nal diameter, fused on to the drawn-out end of the large tube b 
in the blast lamp and finally bent into the U-shape by cautiously 
holding it in the edge of a small Bunsen flame. A sealed-in 
platinum wire leads from the mercury at c to the anode e. A 
paraffined cork (slit to keep it from fitting air tight) serves to 
support b firmly with the capillary close to the wall of the outer 
tube, also to prevent evaporation or spilling of the dilute acid. 
Another cork in b prevents loss of mercury, keeps out dirt and 
supports the other terminal wire. The whole is supported by 
a base of dry, varnished wood. 
Some measurements were made to determine the influence 
