[ 6 9 ] 
an inch, and will prove an unfimnoun table obftacle to 
the feeing any objeCt, unlefs by fome very happy 
accident. 
The other globules, whofe focus is not quite lb 
near, are liable proportionally to the fame inconve- 
nience. 
The very great magnifying power of glafs globules 
is fufficiently well known : many years ago they were 
much ufed, and highly boafted of on that account. 
But they now, long fince, have been laid afide, and 
convex lenfes fubffituted in their room ; and that with 
very good reafon, from the difficulty in the application 
of luch globules, from the deficiency of light, from 
the diftorfion of the image feen, from the painful 
Braining of the eyes, and from the boundlefs latitude 
given to imagination and conjecture, for want of fuf- 
ficient diffinctnefs and precision. 
Nothing can be more injudicious than the defire of 
fuch exceffive magnifying power : whenever we can 
fee an objeCt clearly and well defined, we ought to be 
contented ; all beyond this there is no dependence on. 
In fome letters, fent with thefe glaffes, the Society 
has been favoured with uncommon obfervations on the 
globules of the blood, deferibed as having been viewed 
(it is not faid by thefe glaffes) floating in the ferum, and 
fometimes changing their figure therein : and alfo 
with a long account of the impregnation of vege- 
tables ; wherein we are told, that the exquifitely 
minute corpufcles or feminal particles, emitted 
by the grains of the Farina fcecundans, have been 
feen to enter into, and be conveyed along tubes ex- 
ceeding fmall, which at the time dilated and contract- 
ed 
