CHAPTER VII. 



ORIGIN, DISTRIBUTION, AND CLASSIFICATION OF THE SOILS OF 



NEW-YORK. 



I. ORIGIN OF SOILS. II. DISTRIBUTION OF SOILS : DILUVIAL ACTION ; TRANSPORTATION OF BOULDERS ; SCORING OF 

 ROCKS : CAUSES OF DILUVIAL ACTION : ERA OF DILUVIAL ACTION : FINAL CAUSE OF DILUVIAL ACTION. III. 

 CLASSIFICATION OF SOILS ; ELEMENTS OF SOILS; TEMPERATURE OF SOILS ; RELATIONS OF SOILS TO THE ROCKS 

 ON WHICH THEY REPOSE J ANALYSIS OF SOILS. REMARKS ON CLIMATE. 



In the two preceding chapters, we have given a description of the rocks of the State, and 

 determined their range and location ; and we now proceed to investigate the origin of the 

 soil, and the manner of its distribution. 



I. ORIGIN OF SOILS. 



In describing the rocks of New-York, we have had occasion to refer to the mode in 

 which sedimentary rocks are formed ; the first step in the process being a destructive one 

 upon the solid strata, by which the exposed surfaces are abraded. Several causes combine 

 to produce this result, each of which varies in intensity according to certain circumstances. 

 One of the ordinary effects of water is to dissolve the materials composing a rock, the disso- 

 lution being promoted by the presence of carbonic acid held in solution by the water. All 

 rocks containing carbonate of lime, are dissolved more or less by water charged with this 

 acid. The materials thus dissolved, and held in chemical solution, are not deposited at once. 

 If the water is saturated, or nearly so, the carbonate of lime will separate by crystallization, 

 especially if the fluid be diminished afterwards by evaporation ; and it appears that water, 

 highly charged with carbonic acid, may dissolve a large quantity of solid matter, as car- 

 bonate of lime, magnesia or iron, or other bases. In these instances, all that is required, 

 in order that a deposit should be made, is that a portion of the carbonic acid be set free ; and 

 this takes place when the solution is exposed to the atmosphere. Deposits around springs 

 are formed in this manner : in these cases, however, the matter separated is usually hard 

 and crystalline. In the same manner, deposits, not inconsiderable in extent, may be 

 formed in the ocean. 



