258 THE MICROSCOPE AND ITS LESSONS. 



in the fields. In summer and autumn, when all other 

 plants are hard at work, it rests; in winter it works, filling 

 its little capsules with thousands of spores, and in spring 

 it disperses them. It is the pioneer of vegetation, where 

 before all was desolation ; and this is the order first the 

 moss, then the grass, then smaller ferns, then the larger 

 ones; then the small, and after that, the larger trees. 

 Their motto is what yours and mine must be in our 

 microscopical studies " by little and little." 



Our microscopical " meditation at eventide " would 

 be incomplete without some reference to what is called 

 " polarized light." Should any one ask, What is polarized 

 light? all that can be said is, "Polarized light is 

 polarized light." 



Next to the great and undiscovered mystery of life, 

 light is the greatest of mysteries. -" God is light,' 1 the 

 Bible tells us ; and that metaphor is the best of all 

 metaphors, not only because it is in the Bible, but also 

 because a great deal that we know of God as therein 

 revealed is very remarkably allegorized by light. Our 

 accessories in the study of this important branch of 

 microscopical science consist of a prism and an analyzer : 

 the former is placed under the stage, and the latter 

 nearest the eye ; both are prisms made of Iceland spar, 

 and the thin film of selenite, which greatly assists the 

 polarization, is sulphate of lime, each being a pure and 

 perfect crystallization of chalk, or rather of what is called 

 plaster of Paris; and you will, of course, remember of 

 what chalk is composed in our examination of foraminifera. 

 With these necessary accessories light is chemically 

 analyzed, and it is called " polarized " because it is driven 

 to the poles. Both prism and analyzer owe their properties 

 to thin films in invisible layers, and as the pencils of rays 

 or beams of light pass through them, the compound ray 



