INTRODUCTION. 3 



from clear window glass, or better from photo- 

 graphic plate ; 76 mm. (3 in.) by 25 mm. (i in.) is the 

 standard size. 



Cover glasses must be bought. They should be 15 to 

 20 mm. in diameter or square. No. 2 thickness is pref- 

 erable. 



The compound microscope should be of good work- 

 manship, which can be best secured by buying of some 

 reputable maker. A small low stand is to be pre- 

 ferred. It should have a good fine adjustment and be 

 furnished with two good objectives, viz., a I in., or , 

 and a , \, or , and two eye-pieces, viz., A and C, or if 

 only one, a B. A combination of either eye-piece with 

 the i in., f, or is in this manual designated as a "low 

 power" ; similarly, a combination with the j, , or -J- 

 is known as a " high power." There should also be a 

 camera lucida, and a micrometer ruled in fractions of a 

 millimeter. 



Fine forceps should be of steel, have very slender 

 bent points, and come together accurately. Those used 

 by dentists are excellent. 



A large camels-hair brush \s desirable for dusting off 

 lenses. A small one with long hairs, which tapers to a 

 sharp point when wet, is very convenient for removing 

 sections from the razor. It should be mounted on the 

 small end of a pen-holder, in the large end of which is 

 a short needle. By sticking this in the table the brush 

 may be kept out of the dust and always handy. 



Watch-glasses should have a flat bottom to prevent 

 tipping too easily. Plain individual salt-cellars answer 

 the purpose admirably. 



A dropping-tube is a piece of small glass tubing drawn 



