6 The Microscope. 



connected with the microscope,, free from the bewilder- 

 ment and fatigue which would doubtless attend an 

 actual inspection of a number of instruments. 



The intending purchaser of a microscope, if limited 

 as to price, should at least take care that the micro- 

 scope shows objects clearly, and is perfectly achro- 

 matic, that is, without those fringes of rainbow 

 colours always seen surrounding objects in inferior 

 microscopes. It should also be constructed to 

 lean backward, (see fig. 1, frontispiece,) as being far 

 less fatiguing to the observer than the upright 

 position. It should have at least two different degrees 

 of magnifying, and one of these should be of low 

 power, with large field of view, for the purpose of 

 showing as much as possible of an object at once. 

 These, with the condensing lens and mirror, to throw 

 light on or through objects, are the things indispen- 

 sable. Among the luxuries are screws for moving 

 the stage back and forward, and from side to side ; 

 apparatus for exhibiting the beautiful effects of what 

 is called "the polarization of light," and several 

 additional magnifying powers. An observer with 

 some prospect of leisure, and likely to use the micro- 

 scope a good deal, might do well to purchase an 

 instrument to which additions could be made from 

 time to time. The object-glasses are the most ex- 

 pensive part of the microscope, and the purchase of 

 an additional one therefore adds a good deal to the 

 total cost.* 



* The object-glasses supplied with microscopes are generally 

 known as the "two-inch" power, the "quarter-inch," etc. These 



