Microscopical Essays, 7 



Dr.'Lieberkuhn adapted a microfcope to every objecl ; they 

 confifted of a ftiort brafs tube, at the eye end of which a concave 

 filver fpeculum was fixed, and in the center of the fpeculum a 

 magnifying lens : the objecl was placed in the middle of the 

 tube, and had a final! adjuftment to regulate it to the focus ; at 

 the other end of the tube there was a piano convex lens, to con- 

 denfe and render more uniform the light which was reflected 

 from the mirror. But all this pains was not bellowed upon trifling 

 objecls ; his were generally the molt curious anatomical prepara- 

 tions, a few of which, with their microfcopes, are (I believe) 

 depofited in the Britifh Mufeum. It will be proper, in this place, 

 to give fome account of M. Leeuwenhoek's microfcopes, which 

 were rendered famous throughout all Europe, on account of the 

 numerous difcoveries he had made with them, as well as from his 

 afterwards bequeathing a part of them to the Royal Society, 

 The microfcopes he ufed were all fmgle, and fitted up in a con- 

 venient fimple manner ; each of them confided of a very fmall 

 double convex lens, let into a focket between two plates rivetted 

 together, and pierced with a fmall hole ; the objed was placed on 

 a filver point or needle, which, by means of fcrews adapted for 

 that purpofe, might be turned about, raifed or deprefled at plea- 

 fure, and thus be brought nearer to, or be removed farther from 

 the glafs, as the eye of the obferver, the nature of the objea, and 

 the convenient examination of its parts required. M. Leeuwen- 

 hoek fixed his objects, if they were folid, to the foregoing 

 point with glue ; if they were fluid, he fitted them on a little 

 plate of talc, or exceeding thin blown glafs, which he afterwards 

 glued to the needle, in the fame manner as his other objecls. The 

 gtafles were all exceeding clear, and of different magnifying pow- 

 ers, which were proportioned to the nature of the objedt, and 



the 



