D. Boboulieff—Dissipation of Electricity in Gases. 127 
In order to demonstrate the dependence of this expression on 
the pressure of the gas, we will make use of the following: 
> jit-at, ve 6dH 
u=485 X10 fae, Nm= 7-760-(1--ady 
where the letters have the same meaning as before; we then 
obtain : 
Lie 9 d 
(4) pa 7 ee eae 
that is to say, the coefficient of dissipation in one and the same 
gas Increases in proportion to the pressure. oe 
aking this conclusion for my bond I undertook to investi- 
gate experimentally the dependence of the coefficient of dissi- 
pation on the pressure and properties of the gas. The apparatus 
that I used was constructed in the following manner : 
On the copper plate of an air pump was fixed a bell glass, with 
an opening in its upper part. Into this opening a diaphragm 
was adapted, having a sliding tube plastered carefully, through 
which passed a copper rod, having at its upper end a glass 
handle, and at its lower end a curved prolongation ending with 
a small sphere. To the diaphragm there was attached a silk 
thread, from which hung by the middle a little bar (MN) made 
of shellac, about 100™ long and 1™™ diameter, having on one of 
its ends a little ball made of elder pith covered with gold leaf, 
and on the other a small leaf of mica; by the middle of this bar 
again was fixed, also of shellac, a little rod 40™™ long and 2" 
diameter, carrying at its lower end a short magnetized needle. 
(mn). The ball was immovable, and of the same diameter as 
the movable one. On the outside of the bell glass on a level 
with the bar was pasted a scale (BB) on thin paper divided on 
a : 
mica sheet, 
The air or gases were introduced into the bell glass through 
five drying tubes, of which one was filled with small pieces of 
pumice stone, wetted with sulphuric acid, and another with 
chloride of calcium; under the bell glass stood a small vessel 
containing pieces of phosphoric acid. The experiments were 
performed only after the bell glass had been at least three times 
retilled with such air or gas. 
The shaft or copper rod served to charge the balls, which 
before being charged touched each other; in this position the 
* Clausius, Abhandlungen, II, p. 255. ; . ‘ 
+ Dellmann the quantity of water in the air. 
Zeitechsitt fir dis Mothemadih cea Donkey Soblomiloh. Bend 31, 6 248-352. 
