On the electrical phenomena exhibited in vacuo. 65 
It appeared to me an object of considerable moment, and 
one intimately connected with all these queries, the relations 
of electricity to space, as nearly void of matter as it can be made 
on the surface of the earth; and, in consequence, I undertook 
some experiments on the subject. 
It is well known to the Fellows of this Society who have 
considered the subject of electricity, that Mr. Walsh believed 
that the electrical light was not producible in a perfect tor- 
ricellian vacuum ; and that Mr. Morgan drew the same 
inference from his researches ; and likewise concluded that 
such a vacuum prevented the charging of coated glass. — 
Now it is well known, that in the most perfect vacuum that 
can be made in the torricellian tube, vapour of mercury, 
though of extremely small density, exists ; I could not help, 
therefore, entertaining a doubt as to the perfect accuracy of 
these results, and I resolved not only to examine them expe- 
rimentally, but likewise, by using a comparatively fixed 
metal in fusion for making the vacuum, to exclude, as far as 
was possible, the presence of any volatile matter. 
The apparatus that I employed was extremely simple, 
[PI. V.] and consisted of a curved glass tube with one leg 
closed, and longer than the other. In this closed leg a wire 
of platinum was hermetically cemented, for the purpose of 
transmitting the electricity : or to ascertain the power of the 
vacuum to receive a charge, it was coated with foil of tin or 
platinum. The open end, when the closed leg had been filled 
with mercury or any other metal, was exhausted either by 
being placed under the receiver, or connected with the stop- 
cock of an excellent air pump ; and in some cases, to ensure 
mdcccxxii. K 
