THE COMPOUND MICROSCOPE 



doing, it reduces the magnification of the eyeglass. 

 In instruments provided with more than one eye- 

 piece we shall wish to know which gives the greater 

 magnification ; this is or should be marked upon the 

 metal rim surrounding the eyeglass but, in general, 

 it may be stated that the shorter the eyepiece the 

 greater its magnification. We repeat again, increase 

 your magnification always, when possible, by using 

 higher power objectives rather than eyepieces with 

 greater magnifying powers. Sometimes it is neces- 

 sary to use a greater magnification than our most 

 powerful objective will give us ; then we must fit our 

 most powerful eyepiece and draw out the upper part 

 of the microscope tube — in the best instruments they 

 are made to pull out, after the manner of the tele- 

 scope. The effect of so doing will be to increase 

 the magnification considerably but, at the same 

 time, the definition or clearness is seriously impaired. 

 For the examination of practically all our micro- 

 scopic objects we require a number of slides, little 

 glass slips of good, thin, clear glass. They may be 

 used over and over again unless we make permanent 

 preparations, but we are hardly likely to do so in 

 our early days. The slides are held in place on the 

 microscope stage, either by a pair of clips attached 

 thereto or by resting against a bar running across 

 the stage. We may here remark that it is essential 

 always to keep one's microscope slides absolutely 

 clean. Dirty slides denote the careless worker; 

 moreover, dirt when magnified is misleading. 

 Objects which are being examined in water or any 



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