Sir W. Snow Harris’s Researches in Statical Electricity. 97 
4 feet in length and 1 inch in diameter, and Ea delicate electro- 
meter of the form just adverted to. The cylinder being charged 
with a given measured quantity of electricity, the arm of the 
electrometer inclines toward it a given number of degrees. Let 
this instrument, affected by a given inclination, be now carefully 
moved along against a guide-rail upon a base B: no change 
whatever will ensue in the degree of inclination of the arm. The 
charged cylinder exerts upon it the same force throughout. 
Exp. 11. The cylinder ¢, fig. 14, being suspended as above de- 
scribed, I endeavoured by means of an electroscope of repulsion, 
m q, to discover whether any change would ensue in the divergence 
of the balls in changing their position along the charged surface. 
This electroscope was constructed and applied in the following 
way :—A slender varnished rod of glass, em, fig. 15, attached to 
a small hook m, is cemented into a light cross arm ab of gilded 
wood, about an inch long, being equal to the diameter of the 
cylinder ¢, fig. 14; bc and ad are two light reeds terminating 
in balls of pith hung at each extremity of the crosspiece ad. 
The jointed hinges are made of very fine platinum wire turned 
into rings, and hang one within the other after the method of 
Cavallo. This construction gives to the reeds and balls an ex- 
cessive freedom of motion, and is incomparably the best method 
of suspension for such electroscopes I have as yet met with. 
This electroscope is hung by means of the hooked ring m upon 
a small line of silk a, fig.14, stretched between the wooden balls 
terminating the glass arms supporting the insulated cylinder e. 
When the cylinder is electrified, the balls necessarily diverge and 
stand out freely from it on each side, as shown in the figure. 
Let this electroscope thus divergent be now gently and carefully 
moved along upon the line ad by means of a long slender rod 
of glass applied against the ring m: no appreciable change is 
observed in the divergence of the reeds; it is everywhere the 
same. Ifthe divergent reeds be placed beyond either of the 
extremities of the cylinder, then they are apparently thrown 
outwards as well as sideways, as would necessarily be the case, 
but up to the extremity of the cylinder on either side I have 
never yet been enabled to detect any change such as represented 
in fig. 12; and that, whether by the movement of the electro- 
scope, or by testing the divergence from different points under 
the same charge. 
19. An interesting question here arises as to how far the di- 
vergence of the balls is really the result of repulsive force, pro- 
perly so called. Whether, as maintained by Lord Stanhope 
and many other eminent electricians, the reeds and balls are 
attracted, as it were, into the air rather than absolutely repulsed, 
much in the same way that we observe an excited silk ribbon 
Phil. Mag. 8. 4. Vol. 14, No, 91. Aug. 1857, H 
