62 THE MICROSCOPE. [April, 



QUESTIONS ANSWERED. 



Note. — Dr. S. G. Shanks, of Albany, N. Y., kindly consents to receive all so? ts of ques- 

 tions relating to microscopy , whether asked by professionals or amateurs. Persons of all 

 grades of experience , from the beginner upward, are welcome to the bentfts of this depart- 

 ment. The questions are numbered Jor future reference. 



143. What is the best method foi' mounting starch, pollens, 

 etc.* for the polar iscope? What medium is best, and how 

 may I keep the grains in the centre of the mount ? — Novice. 



Place a small drop of oil of cloves on the centre of a cover- 

 glass, and sprinkle the starch into it. With the corner of a slip of 

 hard, smooth blotting-paper absorb the surplus oil, add a drop 

 of balsam, and set aside, covered from the dust, for twenty-four 

 hours. Drop sufficient balsam on the centre of the slip, place the 

 prepared cover, stiffened balsam side down, in the fresh balsam on 

 the slip. Apply a gentle pressure and let the cover slowly settle 

 against the slip. 



Two or three different sorts of starch or pollen may thus be 

 mounted under one cover; and if carefully done, but little mixing 

 will take place. If the balsam on the cover be well hardened 

 the group or groups will not spread at all. 



J 44. Describe the best way of cleaning diatoms without the 

 use of acids. — E. P. W. 



Put the material in a flask with pure water ; insert a cork with 

 a tube in it. The tube should reach nearly to the water inside the 

 flask, and extend outward a foot or more in length. Boil contin- 

 uously, over a lamp, for several days, or until the diatoms may 

 be seen to be clean. The long tube acts as a sort of condenser and 

 returns most of the steam as water, thus serving to maintain the 

 level of the latter with but small loss. The material may be kept 

 boiling by the hour, without attention. A little soap added will 

 sometimes assist in cleaning away flocculent matter. 



145 '. What is the best way of illuminating opaque objects 

 for examination with \ inch to i~j inch objectives : — E. P. W. 



A bull's-eye condenser or the concave mirror swung above the 

 stage may be used with the lower powers. A Lieberkiihn, which 

 is a concave metallic mirror, affixed to the objective, may be used. 

 This reflector receives the light from the mirror below, and 

 focuses it on the upper side of the object. With the higher pow- 

 ers, Smith's vertical illuminator may be used. This is a re- 

 flector inclosed in an adapter which is screwed to the nose-piece 

 of the microscope, above the objective. The reflector is a thin 

 cover-glass and receives the light from the side, reflects it down 

 through the objective lenses, upon the opaque surface. These 

 instruments may be had at the dealers in optical apparatus. 



