GEOLOGY OF SOIL. 23 



In No. 4, all the phosphoric acid is included in the phos- 

 phate of lime, and iron. This analysis is by Crasso, the 

 others by Hruschauer. 



No. 1 was grown on soil formed from the debris of 

 quartzose rocks, by the decomposition of gneiss, mica-schist, 

 clay-slate, chlorite, hornblende, quartz, and a little lime. 



No. 2, from soil formed of decomposed limestone, variety- 

 called transition. 



No. 3, from soil formed of decomposed mica-slate. 



No. 4, " " " *' " porphyry. 



It is evident, that where the soil has not proceeded from 

 geological drift, as in No. 1, widely different geological 

 formations afford all the mineral elements of plants. 



22. The plants used for food are cultivated on every 

 variety of rock foundation which the earth presents. Their 

 cultivation is limited neither by granitic nor trappean, by 

 fossiliferous or non-fossiliferous rocks. Their product varies 

 not more on different than on the same geological formation. 

 Everywhere, over every variety of rock, the cultivation of 

 the food-bearing plants repays the labor of the farmer. 



23. Surveying Massachusetts, it is evident the grain crops 

 are not influenced by the peculiar rock formations over 

 which they are grown ; for in this State, with the exception 

 of modern volcanic rocks, all the various formations which 

 the earth presents are found. Yet no difference in the 

 quality and quantity of crops of rye, oats, barley, wheat, 

 Indian corn, is found, which can be attributed to different 

 geological tracts. 



24. All plants have a natural limit, a peculiar region, in 

 which, unaided by the human,race, they flourish and spread 

 spontaneously. The smaller the limit of this natural boun- 

 dary, the more difficult is the cultivation of the plant, yet we 

 find that the natural boundary is passed, and so plants come 



