210 THE MICROSCOPE. [October, 



S6. Can you tell me anythijtg abotit a parasite found on the 

 foot of the tiger ? A Scientist^ in the Medical Briefs says it 

 is a counterpart of a tiger in every respect. — S. H. Cowden. 



The " scientist" who gave currency to that yarn is either a 

 humorist or a Chinese laundryman. No such a parasite exists. 



87- How may ca?ze-sugar be detected in honey ? — Amateur . 



Cane-sugar may be detected with a saccharometer, or by dihit- 

 ing with water and carefully crystallizing, the large cane-sugar 

 crystals may be obtained. 



Z^. What does right-hand or left-ha?zd polarization mean ? 

 — Polar iscope. 



The prisms of a polarizer being crossed to produce extinction 

 of light, certain substances introduced between them have the 

 power to partially restore light ; if the analyzer be turned a cer- 

 tain number of degrees, light will again disappear ; this is called 

 the angle of rotation, and may be right-handed or the opposite. 

 Different specimens of quartz, although of similar chemical com- 

 position, may require right or left rotation, because of some in- 

 ternal peculiarity of structure. The different sugars exhibit the 

 same peculiarity. A polarizing instrument called a saccharom- 

 eter employs this principle to detect the different forms of sugar 

 which could scarcely be separated by chemical processes. 



89. Color depends upon the velocity of light. Revolving a 

 polarizer changes colors to their C07nple7ne7itaries. If so., are 

 all minerals uniform in their behavior toward light ? — E. C. 

 Hoyt. 



The behavior of minerals depends upon their thickness, inter- 

 nal structure, and the direction of their axes of crystallization. 

 Polarized light is not precisely similar to ordinary light ; it is 

 something less than ordinary light, and must be studied as a 

 thing of its own kind. A plate of mineral of varying thickness 

 produces tints which follow the law of Newton's rings, but must 

 be much thicker for use with polarized light than with ordinary 

 light. 



90. What is tJie purpose of those crystals in the onion skin? 

 — Botany. 



The crystals are usually oxalate of lime and crystallize from an 

 excess in the sap. They are an excretion. 



9 1 . What is the best work on Petrology .^ and why are not more 

 of the?n written ? — Minerals. 



Petrology is still a young study. Such works are expensive 

 and have a limited sale. See Am. Mon. Mic. Journal, vol ix, 

 pge. 70, a good paper with references to publications in German. 



