THE MICROSCOPE. O 



tages over the simple Microscope. In the first 

 place, by the use of the lenses in the eye-pieces, the 

 object may be magnified to almost any extent. 

 There is, however, a limit to the utility of this 

 magnifying power ; for when objects are greatly 

 magnified, they become indistinct. This is seen in 

 the Oxhydrogen and Solar Microscopes, where the 

 objects are thrown by means of highly magnifying 

 lenses on a white sheet ; and, although made enor- 

 mously large, their details are much less clear than 

 when looked at by a lens magnifying much less. 



Compound Microscopes are generally fitted up 

 with two eye-pieces, one shallow and the other 

 deep. The first has its lenses close together, and 

 magnifies the most, whilst the other has them fur- 

 ther apart, and magnifies less. In the use of these 

 eye-pieces, it should never be forgotten that the 

 one which magnifies least is generally the most 

 trustworthy. 



The Compound Microscope is now, undoubtedly, 

 one of the most perfect instruments invented and 

 used by man. In the case of all other instruments, 

 the materials with which they are made, and the 

 defects of construction, are drawbacks on their per- 

 fect working ; but, in the Compound Microscope, 

 we have an instrument working up to the theory 

 of its construction. It does actually all that could 

 be expected from it, upon a correct theory of the 

 principles upon which it is constructed. Neverthe- 

 less, this instrument did not come perfect from its 

 inventor's hands. Its principles were understood by 

 the earlier microscopic observers in the seventeenth 

 and eighteenth centuries, but there were certain 

 drawbacks to its use, which were not overcome till 

 the commencement of the second quarter of the 

 present century. 



These drawbacks depended on the nature of the 



