818 THE SEASON WHY. 



" Thou art the God that doest wonders." PSALM ixxvn. 



1257. What is tannin ? 



Tannin is a vegetable production, obtained chiefly from the oak- 

 bark, and from a variety of other vegetable sources. It possesses 

 the peculiar chemical property which renders it valuable in tanning 

 leather. 



1258. What is opium? 



Opium is the produce of the poppy, and is obtained from the seed. 



1259. What are vegetable dyes ? 



Vegetable dy3s are the various colours derived from the secretions 

 of plants, such as indigo, madder, logwood, allcanet-root, Sfc. 



1260. What is silica ? 



Silica is a mineral substance, commonly known as flint ; and it 

 is one of the wonders of the vegetable tribes, that, although flint is 

 so indestructible that the strongest chemical aid is required for its 

 solution, plants possess the power of dissolving and secreting it. 

 Even so delicate a structure as the wheat straw dissolves silica, 

 and every stalk of wheat is covered with a perfect, but inconceivably 

 thin coating of this substance. 



Amid all the wonders of nature which we have had occasion to explain, there 

 is none more startling than that which reveals to our knowledge the fact that a 

 flint stone consists of the mineralised bodies of animals, just as coal consists of 

 masses of mineralised vegetable matter. The animals are believed to have been 

 infusorial animalculae, coated with silicous shells, as the wheat straw of to-day 

 is clothed with a glassy covering of silica. The skeletons of animalcules 

 which compose flint may be brought under microscopic examination. Geologists 

 have some difficulty in determining their opinions respecting the relation which 

 these aiiimalculse bear to the flint stones in which they are found. Whether 

 the animalculae, in dense masses, form the flint; or whether the flint merely 

 supplies a sepulchre to the countless millions of creatures that, ages ago, enjoyed 

 each a separate and conscious existence, is a problem that may never be solved. 

 And what a problem ! The buried plant being disentombed, after having 

 lain for ages in the bowels of the earth, gives us light and warmth; and the 

 animalcule, after a sleep of ages, dissolves into the sap of a plant, and wraps the 

 coat it wore, probably " in the beginning, when God created the heavens and the 

 earth, and when the earth first brought forth living creatures," around the 

 Blender stalk of waving corn ! 



1261. Why is silica diffused over the stems of tvheat, 

 grasses, canes, Sfc. ? 



Because it affords strength, density, and durability, to structure* 



