22 Mr, cavallo’s Account of fome 
The principal part of this inftrument is a glafs tube 
cdmn, cemented at the bottom into the wooden piece 
ab, by which part the inftrument is to be held when 
ufed for the atmofphere, and it alfo ferves to fcrew the 
inftrument into its wooden cafe abo, fig. i. when it is 
not to be ufed. The upper part of the tube cdmn is 
fhaped tapering to a fmaller extremity, which is entirely 
covered with fealing wax melted by heat, and not dif- 
folved in fpirits. Into this tapering part a fmall tube is 
cemented, which, with its under extremity, touches the 
flat piece of ivory h, fattened to the tube by means of 
cork. The upper extremity of the wire projects about a 
quarter of an inch above the tube, and fcrews into the 
brafs cap ef, which cap is open at the bottom, and ferves 
to defend the waxed part of the inftrument from the 
rain, &c. In fig. 3. this brafs cap is reprefented as tran- 
fparent, in order to (hew its internal fhape, and the man- 
ner in which it is fcrewed to the wire projecting above 
the tube l. The fmall tube l and the upper extremity 
of the large tube cdmn appear like one continued piece, 
on account of the fealing wax which covers them both. 
The conical corks p of this electrometer, which by their 
repulfion fhew the electricity, 8cc. are as fmall as they 
can conveniently be made, and they are fufpended by ex- 
ceedingly fine filver wires: thefe wires are fhaped in a 
ring 
