[ 364] 
in exhaufting, defeated the intent by conducting 
the electricity, and thereby preventing its accumu- 
lation. Secondly, the more complete the vacuum 
was, ccctcris paribus , the more confiderable were 
the effects: and here I fhould not do julfice to 
real merit, were I filent in regard to Mr. Smeaton. 
This gentleman with a genius truly mechanical, 
which enables him to give to fuch philofophical in- 
ftruments, as he executes, a degree of perfection, 
fcarce to be found elfewhere ; this gentleman, I fay, 
has conffructed an air-pump, by which we are im- 
power’d to make Boyle’s vacuum , much more per- 
fect than heretofore. By a well-conducted experi- 
ment, which admits of no doubt as to its truth, I 
have feen by this pump the air rarefied to a thoufand 
times its natural flate ; whereas commonly we feldom 
arrive at above one hundred and fifty. As the pro- 
motion of the mechanic arts is a confiderable objeCt 
of our excellent inftitution, if this gentleman could 
be prevailed upon to communicate to the Royal 
Society that particular conftruCtion of his air-pump, 
which enables it to execute fo much more than thofe 
commonly in ufe, it would not fail to be an accept- 
able prefent : but to return : 
The experiments treated of in this paper muff be 
confidered to have been made in this vacuum . The 
electrical machine, with its prime conductor, need 
here no particular defcription ; but that of the glafs, 
in which the vacuum was made, fhould be more 
minutely confidered. It confifted of a glafs tube 
nearly three feet in length, and of almoft three inches 
in diameter. A ring of brafs, exaCtly fitting this 
tube, was cemented to both its extremities, into each 
of 
