r 5** ] 
nifies not near enough to fhew the Animalcules in the 
Semen of that Flea. 
I am fenfible, that Mr. Leeuwenhoek , by long 
Practice, and uncommon Attention, might be able to 
difeern many Objeds with thefe MicKdcopes, which 
others, lefs accuftomed to Obfervations of this kind, 
cannot readily do: His Eyes too might be fomewhat 
different from the Standard I meafure by. But all 
thefe Allowances will not, I think, fuffice to re- 
concile the Paffages I have quoted with the Powers 
of the Glades under Examination. 
While I was overlooking thefe Microfcopes of Mr. 
Leeuwenhoek , an Opportunity prefented of examin- 
ing and comparing with them a curious Apparatus 
of Silver with Six different Magnifiers, belonging to 
Mr. Folkes , and then newly made for him by Mr. 
Cuff, in Fleetftreet. The Body of this Inftrument, 
into which the Glades are occafionally to be fattened, 
is after the Fafhion of JVilforis Pocket Microfcope, 
and contrived to ferew into the Side of a Scroll 
fixed on a Pedeftal, from which a turning Speculum 
refleds the Light upwards upon the Objed : It is like- 
wife contrived to be ufed with the Apparatus of the 
Solar Microfcope : Defcriptions and Figures of both 
of which I have fince given in a Book intituled. The 
Microfcope made eajy. Edit. 2d. Lond. 1743. 8 °. 
I meafured the focal Diftances, and magnifying 
Powers, of the Six Glades, and found them to be as 
follows : 
