102 MICROSCOPIC OBJECTS. 



" The passage which I beheve led the Doctor to the 

 discovery alluded to is here transcribed : — ' If we examine 

 the wings of this creature (Silkworm Moth) by the mi- 

 croscope, we shall find them covered with an incredible 

 number of feathers, of such various forms, that if a 

 hundred or more of them were to be seen lying tog-ether, 

 each would appear of a different shape. To show more 

 clearly this wonderful object, I caused eight feathers to 

 be delineated ; for I do not remember that I ever saw 

 them of so curious a make in any flying insect. Although 

 the microscope by which these feathers were drawn 

 represented objects very distinctly, the hmner could not, 

 through it, see the ribs or streaks in each feather until I 

 pointed them out to him. Therefore I put into his hands a 

 microscope which magnified objects almost as much as 

 that by which the silkworm's thread was drawn, desiring 

 him to give the figure of that feather wliich through it 

 he could see the most distinct.' — Selec Works, p. 6Z. 



"In this passage one point is very remarkable; namely, 

 the incapacity of the artist to see the object unless a 

 higher power was used than that which Leeuwenhoek 

 employed. 



"Having ascertained that fferent test-objects require 

 different degrees of perfection in the instrument used to 

 develop their structure, it became an interesting pursuit 

 to discover those which are best adapted for this purpose, 

 and the peculiarities in the illumination, &c., under which 

 they are exhibited with the greatest perspicuity. In this 

 investigation, it was found that there were two distinct 



