82 



BIOLOGY AXD ITS MAKERS 



Nicrstrasz from the specimen in possession of the University 

 of Utrecht. The instrument consists of a double copper plate 

 in which the circular lens is inserted, and an object-holder — 

 represented in the right-hand lower figure as thrown to one 



Fig. 19. — Leeuwenhoek's Microscope. 

 Natural size. From Photographs by Professor Nierstrasz, of Utrecht. 



side. By a vertical screw the object could be elevated or 

 depressed, and by a transverse screw it could be brought 

 nearer or removed farther from the lens, and thus be brought 

 into focus. 



Fig. 20a shows the way in' which the microscope was 



