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LXVIII. On a New Electrometer (the Siphon Electrometer) for 
measuring the Electrical Charge of the Prime Conductor of a- 
Machine ; and on the Dispersion of different Liquids by Elec- 
trical Action. By Tuomas Tate, Esq.* 
age electrometer most commonly used by electricians, for 
ascertaining the intensity of the charge of the prime con- 
ductor of a machine, is Henley’s. According to the experiments 
of Sir W. Snow Harris, it appears that the degrees of diver- 
gence of this instrument for high charges are nearly in proportion 
to the quantities of electricity generated; at the same time it must 
be observed that this result does not agree with what theoretical 
imvestigation would give. This instrument therefore would 
serve very well in all ordinary cases for indicating the power of 
any machine, provided that all the instruments used were con- 
structed exactly alike; but this is practically impossible; and 
hence it follows that the degree of divergence of one instrument 
cannot be compared with that of another instrument, as regards 
its indication of electrical charge. The hydrostatic and balance 
electrometers are very complete instruments as regards scientific 
research ; but it must be allowed that they are too delicate in 
their construction and mode of action to be used on ordinary 
occasions, when only an approximate value of an electric charge 
is required; moreover, the thermo-electrometer is only appli- 
cable to high charges of an electrical battery. 
The siphon electrometer, represented in the annexed diagram, 
is sufficiently delicate and reliable in its indications, and admits 
of being constructed so that the results derived from one imstru- 
ment may be fairly compared 
with those derived from an- 
other instrument. It depends 
on the principle, that differ- 
ent quantities of electricity 
discharge different quantities 
of liquid from a siphon-tube 
in which the liquid is sus- 
pended by capillary action. 
A B a glass jar, containing 
water, about 4 inches in dia- 
meter, placed upon the insu- 
latmg stand CD of gutta 
percha; EG a small siphon 
about °15 of an inch diameter, 
cemented to the side of the 
jar, as shown in the diagram ; 
HI a funnel-shaped receiver 
* Communicated by the Author. 
