34 THE MICROSCOPE. [February, 



IJJ. Is there any method for tempering the paraffin to the 

 density of a section so that it will cut evenly? If so, what is 

 it?—R. 



Paraffin is not usually tempered for this purpose. It is graded 

 to have a certain melting point or hardness, which will cut 

 smoothly at a certain temperature of the surrounding air. If the 

 paraffin proves to be too hard, by crumbling or otherwise, raise 

 the temperature of the air in the room, or reimbed the specimen, 

 using more of the soft wax. A hard paraffin will allow a very 

 thin section to be cut, but it rolls tightly and is very troublesome 

 to flatten. A very soft paraffin does not support the tissue well. 

 It will crowd up or wrinkle or break. A paraffin melting at 125 

 F. will usually cut well at a temperature of 70° F. 



/Jj.. What microscope can a beginner get for little money, 

 that will be of soine use to him? 



For a beginner the Excelsior Microscope, listed at $2.75, can 

 be recommended. This instrument consists of a small oblong 

 box containing a mirror, and a rod which can be erected ; also a 

 pocket magnifier with three lenses, and an adjustable stage 

 which will slide upon the rod. The whole forms an easily used, 

 simple microscope. But one cannot do much real work without 

 a compound microscope. The cheapest one that will be at all 

 satisfactory will cost at least $2S. 00. Theso-called " School " or 

 •• Household " microscopes, or other such cheap instruments, are 

 worse than none, because their imperfect and misty definition 

 will do much to discourage a student. A microscope, if good, 

 will not only aid study but encourage it. 



SCIENCE-GOSSIP. 



To Preserve Impressions of Leaves. — Those who desire 

 to preserve impressions of leaves of trees and plants can do so in 

 the following simple manner : At any druggist's get a nickel- 

 worth of bichromate of potash, and put it in a 2-oz. bottle of soft 

 (rain) water. When the water has dissolved as much as it will 

 of the potash, pour off the clear liquid into a shallow dish. On 

 this float a piece of ordinary writing-paper till it is thoroughly sat- 

 urated. Let the paper be hung on a piece of string in the dark 

 until it gets nearly dry, when it should be in color a bright yel- 

 low. On this put the leaf, and under it a piece of black cloth 

 and several sheets of newspaper. Put these between two pieces 

 of clean window-glass of the same size, and hold them together 

 with spring clothes-pins or with spring clips similar to those 

 used for holding letters or bills. Expose to a bright sun, placing 

 the leaf so that the sun's rays will fall upon it as nearly perpendic- 

 ular as possible. In a few minutes it w r ill begin to turn brown, 



