[ 68 ] 
They are globules of glafs, formed over a lamp, by 
Father di Torre, and ingenioufly placed in cells of 
brafs, adapted to Wilfon’s microfcope. Four of thefe 
cells, thus furnifhed, were fent as a prefent from the 
Father to this Society, under the care of our late worthy 
member Sir Francis Eyles Stiles : but when they 
came into Mr. Baker’s hands, one of thefe minute 
glades was wanting, having probably been fhaken out 
of its cell in carriage : the lofs, however, fignifies little, 
as there remains another of the fame magnifying 
power. 
Thefe globules are wonderfully fmall : the larged: 
being in diameter only two Paris points, and faid to 
magnify the diameter of an objedt 640 times: the 
fecond is the fize of one Paris point, magnifying the 
diameter of an objedt 1280 times; and the third is 
fo extremely minute, as to be no more than one half 
of a Paris point, or the 144th part of an inch in diame- 
ter, and is faid to magnify the diameter of an objedt 
2560 times, and confequently it muff magnify the 
fquare of fuch diameter 6,553,600 times. 
Now as the focus of a glafs globule is at the di- 
ftance of .ith of its diameter, it is with the utmoffc 
difficulty that globules fo minute as thefe can be 
employed to any purpofe. For inflancc, the focus 
of that globule, whofe diameter is but one half of a 
Paris point (or the 144th part of an inch) is no far- 
ther from the objedt to be examined, than the 576th 
part of an inch. In attempting to find this focus, it is 
fcarce poffible to avoid touching the objedt with the 
glafs, if it be not placed between laminae of talc or 
ifinglafs ; and if it befo placed, even the thinned talc 
bears a confiderable proportion to this 576th part of 
an 
