SOCIETY OF CENTRAL ILLINOIS. 2/il 



That portion, the smaller portion, of the broken-down rocks, 

 which is carried away in solution, sinks deeper into the rocks, and 

 then does wondrous work. It breaks down some of the silicates, and 

 fills their places with very different substances, formed by the union 

 of the base of the silicate with another acid. It abstracts from a 

 compound silicate a single constituent, and replaces it with another. 

 It enters into the structure of a mineral, and, without in the least 

 altering its composition, it so modifies the action of the crystalline 

 forces as to effect a material change of form; or, escaping into some 

 fissure, it deposits on its sides a portion of its load, and changes the 

 fissure into a mineral vein. But, no matter what its underground 

 work might have beeji, it all, sooner or later, finds its way to the 

 surface, and is carried through creeks and rivers to the ocean. 

 There some portions are taken up by living forms, and converted into 

 coral sands, shell beds, etc., while the remainder meets with condi- 

 tions which cause its precipitation. This precipitated material, com- 

 ing in contact with the gravels, sands and clays formed by running 

 water, and the coral sands, shell beds, etc., consolidates them into 

 conglomerates, grits, sandstones, shales and limestones. In this way, 

 water, aided by such gases as came within its reach, was able to 

 break down the silicates of the crystalline rock, and from their debris 

 to form all the different kinds of which we know anything. Water, 

 acting through millions of years, has covered the black and ugly 

 primitive rock with a beautiful variegated mantle. 



But no sooner were the rocks so formed elevated above the sur- 

 face of the ocean by the contractile forces of the earth than rain- 

 water began its destructive work upon them also. Working its way 

 into their pores, it broke up the cement which held their particles 

 together, dissolving some, and leaving the others in the loose condi- 

 tion with which We are familiar in our soils. Now, as the soils, so 

 formed, are simply disintegrated particles of the underlying rocks, 

 and as, owing to the instability of the currents which produced 

 them, the composition of the rocks varies through infinite grada- 

 tions, it is easy to account for the variety of soils. Again, as the 

 water which sinks into the rocks has been shown to be the active 

 agent in the production of soils, so that which runs over their sur- 

 face is continually taking up their particles and bearing them away. 

 If the conditions favor such action, the soil will be carried away as 

 fast as formed, and though in more sheltered localities it accumu- 

 lates, — sometimes to the depth of several feet, — still this denuding 

 action is steadily going on, and the underground forces must be ever 

 active to keep it intact. Nor is this denudation to be looked upon in 

 most cases as an evil, for the ingredients which enter most largely 

 into the composition of the soil are not those which are most needed 

 for the nourishment of the plant, and, if the soil were to remain 

 intact, this nutritive material, existing, as it does, in relatively small 

 amount, would soon disappear from that portion of the soil which is 



