142 THE AMEEICAN MONTHLY [Aug 



of an earth worm. The acid will finally dissolve the fibre. 



Polarized Light. — The following rather unreliable 

 but curious rapsody is copied from an old school chem- 

 istry : — "Fancy yourself in a region solely illuminated 

 by Aurora borealis, imagine a country where every pass- 

 ing cloud throws a diverse colored shadow of gorgeous 

 hues across your ' path, where the air breeds rainbows 

 without the aid of a shower, and where the summer 

 breeze breaks these rainbows into irregular lengths, frag- 

 ments and glittering dust, scattering them broad-cast 

 over the land, like autumnal leaves swept by a gale from 

 the forest and you have an approximate, and by no 

 means exaggerated idea of the ejffect of polarized light on 

 substances capable of being affected by it. For it is 

 light endowed with extra delicacy, sublety and versitility. 

 it renders visible minute details of structure in the most 

 glaring colors ; it gauges crystalline forms of infinitesi- 

 mal thinness ; it betrays to the student's search otherwise 

 in appreciable differences of density or elasticity in the 

 various parts of tissues. Indeed, as a detector, polarized 

 light is invaluable, acting the part of a spy under the 

 most unexpected circumstances. It denounces as cotton 

 what you believed to be silk ; it demonstrates disease 

 where you supposed health. It adorns objects that are 

 vile and mean, whose destiny is only to be cast out — 

 such as paring of . nails, shavings of animal hoofs, cuticle 

 rubbed or peeled from the stems of plants, offscourings 

 of our kitchens and store rooms, sugar, acids and salts — 

 with the most magnificent, the most resplendent tints 

 such as are seen when the sun streams through the 

 stained glass windows of a Norman cathedral. 



Unrestrained Imagination. — It is always wise in 

 science, to be calm and to avoid exaggeration. Many 

 young microscopists are apt to permit the uninitiated 

 to deceive themselves as to the magnifying power of 



