( 45 *' ) 
doing Mr. heeuwenhoek the Honour of a Vifit at T>elft^ 
and viewing his Curiofities with great Satisfadion^ he 
prefented her with a Couple of his Microfcopes, which, 
as I have been inform’d by one who had them a confi- 
derable Time in his Hands, were of the fame Sort as 
thefe, and did not any ways differ from one of the 15 
Cafes contain’d in the Drawers of this Cabinet. 
The Glaifes are all exceedingly clear, and ihew the 
Objed very bright and diftind, which muft be owing 
to the great Care this Gentleman took, in the Choice of 
his Glafs, his Exadnefs in giving it the true Figure ^ 
and afterwards, amongft many, referving fuch only for 
his Ufe, as he, upon Tryal, found to be mod excel- 
lent. Their Powers of magnifying are different, as 
different Sorts of Objeds may require^ and, as on the 
one Hand, being all ground Glalles, none of them are 
fo fmall, and confequently magnify to fo great a De- 
gree, as fome of thole Drops, frequently us’d in other 
Microfcopes^ yet, on the other, the Diftindnefs of 
thefe very much exceeds what I have met with in the 
Glaffesof that Sort ^ and this was what MxXeeuwenhoek 
ever principally propos’d to himfelf, rejeding all thofe 
Degrees of magnifying in which he could not fo well 
obtain that End 5 for he informs us in one of his Let- 
ters, where he is fpeaking of the exceflive Praife fome 
give to their Glaffes on this Account, that although he 
had above Forty Years had Glaifes by him of an extra- 
ordinary Smallnefs, he had made but very little Ufe 
of them 5 as having found, in a longCourfe of Experi- 
ence, that the mod confiderable Difcoveries were to be 
made with fuch Glaifes as, magnifying but moderately, 
exhibited the Objed with the mod perfed Brightnefs 
and Didindion. 
Z z z 2 
But 
