6S 



GENESEE FARMER. 



Mar- 



[ Editorisd Correspondence of the Genesac Farmer. ] 



Agricultural Geology. 



All soils are formed by the breaking up into 

 fragments, by frost and other mechanical agents, 

 and the solution and chemical decomposition of 

 rocks. Hence, if we would understand the true 

 character and capabilities of any cultivated earth, 

 we must study the parent rocks from which the 

 soil was derived. Indeed, so general is this law 

 that alluvium, or bottom lands, form no excep- 

 tion to the rule. The broad flats of the Savan- 

 nah, which are occasionally flooded at high 

 water, furnish a case in point. Compared with 

 the ordinary uplands of Ontario, Monroe, Or- 

 leans, and Niagara counties, in Western New 

 York, these beautiful river bottoms in the neigh- 

 borhood of Augusta are poor land. Why is this ? 

 The subject is one of much interest in an agri- 

 cultural point of view. 



Judging from their appearance, one would say 

 that the flats of the Savannah are quite equal to 

 those of the far famed Genesee in fertility. The 

 soil of the former contains a plenty of organic 

 matter, and a due proportion of sand, clay, and 

 iron. A superficial farmer would say that is 

 enough — the land must be productive. Com- 

 pared with the very sandy, sterile pine lands of 

 South Carolina and Georgia, it is. But, com- 

 pared with the ordinary uplands on the Niagara 

 and Caledonia limestone rocks, or those on the 

 Onondaga salt group and Genesee shales, these 

 granitic river flats are poor indeed. They need 

 a good deal of manure, and that very often. 



Give lo a skilful agricultural chemist a gallon 

 of the water of the Genesee river at Rochester, 

 when running perfectly clear, and a like quan- 

 tity of the river water which flows in a stream 

 about as large as the Hudson at Troy, by this 

 city, (Augusta,) and he could, without know- 

 ing anything of either country, say that the for- 

 mer drained a fertile and the latter a compara- 

 tively poor agricultural region. The salts of 

 lime, magnesia and soda found in the water of 

 the Genesee, would inform the analytical chemist 

 and geologist very correctly of the character of 

 the soils and rocks through and over which the 

 rains from the clouds had passed, before their 

 converging waters arrived at the falls in Roches- 

 ter. If all the fertilizing constituents of wheat 

 and other cultivated plants that flow annually into 

 the basin of lake Ontario, could be equally spread 

 over the soils in the Atlantic States, which lack 

 the su/phales, phosphates and chlorides of lime, 

 magnesia, soda and potash, their productive pow- 

 er would be double what it now is. 



I have taken a lively interest in studying the 

 rocks and soils in this quEirter of the Union. — 

 The celebrated "sand hills," near this city, have 

 a base of rock equivalent to the Potsdam sand- 

 stone in St. Lawrence county, N. Y. As one 

 goes north it becomes micaceous, and gradually 



changes to a hard felspathic rock. Above thia 

 lies a large mass of hornblende, surrounded by 

 syenite ; and farther up (some eiglit miles from 

 Augusta at the head of the Rapids,) we reach 

 [ hard crystalline granite, in the bed of the river 

 and in islands. It is only in isolated patche?- 

 that the latter rock has been forced up from be- 

 low, by some prodigious volcanic effort, at a 

 remote period in the world's history. As all 

 sedimentary strata, like the rocks in Western 

 New York, Ohio, Indiana, Michigan, and Illi- 

 nois, are formed of disintegrated and dissolved 

 igneous* rocks, it is useful to study the latter ta 

 learn the origin and properties of the former. 



Ignecus rocks are unstratified, and very vari- 

 ous in their outward appearance and chemical 

 constitution. The abundant are known by the 

 names of granite and syenite. The former is a 

 compound of the minerals quartz, mica and fel- 

 spar. Syenite differs from the above in having 

 no mica, but hornblende in its place. 



When granite rocks are decomposed, the 

 quartz forms the vast tracts of sand which may 

 be seen to good advantage south of the Allega- 

 nies, in North and South Carolina and Georgia, 

 Felspar makes a tenaceous clayey soil that usu- 

 ally abounds in iron. This mineral forms the 

 " red lands" in the States named. The parent 

 rock out of which they are mostly made has the 

 following composition : 



Silica, 66.75 



Alumina, 17.50 



Potash, 12.00 



Per oxide of Iron, - 2.50 



Lime, .- 1.25 



100.00 

 While slowly weathering and decomposing, 

 felspar loses a large share of its poias/i, which is 

 readily dissolved in rain water, as it falls from 

 heaven, and washed away. Many of the red 

 soils and a portion of the sandy ones in this re- 

 gion abound in mica. They are termed " ising 

 glass lands," Mica has the following composition : 



Silica, - - 49.38 



Alumina, - 23.66 



Potash, - 15.29 



Per oxide of Iron, - - 7.31 



Lime, 6.13 



101.77 

 It is proper to remark that, some mica con- 

 tains magnesia in place of lime, and some fel- 

 spar soda in place of potash. Such felspar is 

 called abhite, from its white appearance. 

 Hornblende contains the following constituents : 



Silica, - 45.69 



Magnesia, 18.79 



Lime, 13.38 



Alumina, 12.18 



Iron, 7.32 



Manganese 0.22 



Fluoric acid, - 1.50 



99.53 



* Igneous" from ignis — fire. Rocits which were once 

 melted like lava, are called " igneous, " and usually crjrB- 

 talize like icp nn'3 granite on cooling. 



