£ 368 ]

*

C H A P. XVII.

OF ME. YOLTA’s CONDENSING P'1/ATES; ok, ofTHE ADVANTAGES WHICH MAY BE DERIVEDFROM AN IMPERFECT INSULATION; AND OFRENDERING VERY SENSIBLE VERY SMALLDEGREES OF NATURAL AND ARTIFICIALELECTRICITY.*

A Conductor, properly constructed for makingobservations on atmospherical electricity, seldomaffects the most sensible electrometer when thesky is free from electrical clouds; but, by meansof the apparatus now to be described, it will ap-pear, that these conductors are always electrical,and consequently the air that surrounds themmust be at all times electrified. This method notonly determines the existence, but also the qualityof the electricity, whether positive or negative,and that, even when the conductor will not attractthe finest thread; but, if a very small attractionis visible in the conductor, then the apparatuswill give long sparks.

The electrophorus used for this purpose, maywith propriety be termed a micro-electrometer,condenser of electricity.

* Phil. Trans.