MICROSCOPIC OBJECTS. 101 



of objectives and eye-pieces ; but even with these, if it 

 is sufficiently small and delicate in its construction for the 

 high powers, it will be too weak for the lower ones, and 

 vice versa. In short (to use an expression which has 

 been apphed to the telescope,) we may as well expect to 

 have the properties of a high-bred racer and a heavy 

 cart-horse combined in the same animal, as the union, 

 perfect in one instrument, of the capabihties I have 

 described. 



"This chapter, be it remembered, is devoted more 

 especially to the investigation of the deeper and more 

 powerful class of microscopes and engiscopes. 



" In the perusal of the works of Leeuwenhoek, Dr. 

 Goring met with a passage describmg the dust or im- 

 bricated scales which cover the wings of the silkworm 

 fPkal(Ena Mori) , from which he was led to suspect there 

 w^ere some pecuhar properties in the lines on the feathers 

 and scales of insects, rendering them more difficult to be 

 discerned than other microscopic objects ; and the result 

 of his investigation was the discovery of their properties 

 as TESTS — a description of objects before unknown in the 

 annals of microscopic science. 



" Now it is undoubtedly of the highest importance to 

 the naturalist that he should know the exact capabilities- 

 of his instrument, in order that he may not be led astray 

 in his investigations by placing undue confidence in it ; 

 and as these tests offer the best means of accomplishing 

 this end, I conceive them to be of the highest value and 

 interest. 



