96 NATURALISTS' ASSISTANT. 



tage to import the lenses of either Hartnack or Zeiss and 

 have them fitted by an "adapter" to his microscope. By 

 this method, he will obtain good objectives at about half the 

 prices charged for similar lenses of no better quality made 

 by American opticians. 



Binocular microscopes have of late been extensively ad- 

 vertised, but for work possess not the slightest advantage and 

 are only manufactured so that the makers may add to the 

 prices and to the profits made on their instruments. 



THE USE AND CARE OF THE MICROSCOPE. 



It is a difficult task to give directions for the use of the 

 microscope as the varying .uses to which it is put require as 

 varied a method of handling. All objects for the micro- 

 scope should be mounted either temporarily or permanently 

 on a glass slide. If it be a moist tissue or an object taken 

 from the water, a drop of water should be placed on the 

 slide, the object placed in it and the whole covered with a 

 piece of thin glass. The slide and its object are now ready 

 for examination. The microscope should now be made ready 

 and the objectives screwed on. It is best to use first the 

 lower powers and then the higher if necessary, with either 

 reflected or transmitted light according as the object is 

 opaque or transparent. There are several advantages con- 

 nected with this method of treatment, one being that in this 

 way a general idea of the structure is first obtained and the 

 various details are studied afterward. It is also much easier 



