SOILS. 13 



order of vegetation subsisting upon elements contained 

 in the air and in the crude rock. Not many years 

 elapse until the moss thickens to such an extent that it 

 appears to be growing in a thin bed of soil, while di- 

 rectly beneath it the rock is decomposed and portions 

 of it drop away in scales as soon as the covering is 

 removed. This is accomplished by the combined ac- 

 tion of heat moisture and the changes incident to cli- 

 matic influences. The mosses continue to grow, bits of 

 decomposed rock drop and lodge at the base, forming 

 a shelving bed of soil which readily supports vegetable 

 growth. Rains possibly wash it away to some low val- 

 ley, there to be mingled with decomposed rocks from 

 other localities, all of which in time build the fertile soil. 

 In it may be found numberless kinds of rocks, and as 

 vegetation increases portions of organic matter mingle 

 with the material and contribute the humus so valuable 

 for the production of certain crops. It seems incredible 

 that the hardest of rocks known should succumb to the 

 action of climate and be reduced to a condition of impal- 

 pable fineness, yet a little observation ortthe part of the 

 investigator will confirm the statement. The reader 

 has doubtless observed a tree growing upon an appar- 

 ently dry rock. A nearer view discloses crevices which 

 the roots of the tree have penetrated. The crevices 

 are lined with rock in all stages of disintegration which 

 increase year by year with the growth of the tree. 

 Further than this, the force of the wedge which the 

 root forms splits off a ledge of rock which in turn 

 disintegrates and adds to the volume of forming 

 soil. 



A ledge of red shale disintegrates rapidly under 



