82 BIOLOGY AND ITS MAKERS 



Nierstrasz 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. 2oa shows the way in which the microscope was 



