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muft certainly have been much greater Magnifiers 
than any in our Pofteflion. And we are affured 
by himfelf, that fuch he had for he often mentions 
his fhifting Objects from his common to his better, 
and thence to his moil exquifite Microfcopes: And, 
befides, (in the Second Volume of his Works, Part 
lid. pag. 290.) he fays, “ Mihi quidem funt centum 
“ centumque Micro fcopia, &c. “ l have an hundred 
“ and an hundred Microfcopes, moft whereof are 
“ able to fhew Objeds fo diftindly, even in the 
“ cloudieft Weather, and by Day-light only, that if 
“ the Animalcule in Semine mafculino of Animals 
“ had the Extremity of their Tails forked, (as de- 
fC fcribed by a certain Writer) I Ihould eafily have 
“ difcovered it. 5 ’ Among this Number, many, 
without doubt, were contrived for the Examination 
of Fluids, fince great Part of his Obfervations were 
made on them : He informs us alfo, that his Method 
was to put them into an exceeding fmall or capillary 
Tube of Glafs, which there does not feem to be any 
Means of applying to the Microfcopes in our Ca- 
binet, even had they been at Liberty ,* and much lefs 
for the larger Tubes he made ufe of to view the Cir- 
culation of the Blood in Frogs, Eels , Fifbes, &c. his 
Apparatus for which we find in the Fourth Volume 
of his Works, pag. 180. — ~But to proceed : 
Mr. Leeuwenhoek , in a Letter to this Society 
concerning the Animalcula obferved by him ifn the 
Semen mafculinum of a Dog, which he defcribes and 
gives a Draught of, fays, they were fo minute, that 
he believed a Million of them would not equal the 
Size of One large Grain of Sand. Vol. 1 . Part I. pag. 
1 < 5 o. Again, in his 113th Letter, fpeaking of the 
Semen 
