ISIS). 



THE GENESEE FARMER. 



21 



1 SCIENTIFIC AGRICULTURE." - GEOLOGY. 



Last month we briefly noticed a work entitled 

 "Scientific Agriculture," by Dr. M. .M. Rodoers, 

 recently published by E. Darrow, of this city. Since 

 then we have given the volume a more careful ex- 

 amination) and find thai its pages contain a large 

 amount of valuable scientific information. It em- 

 braces the elements of Chemistry, Geology, Botany, 

 and Meteorology, as applied to Practical Agriculture ; 

 and each subject is discussed in a brief, plain, and 

 comprehensive manner. The work is a good one 

 for the young, or new beginners in these sciences. 

 The annexed extract is from the department devoted 

 to Geology : — 



GEOLOGY. — DEFINITION OF TERMS. 



Rocks are divided into two great classes, viz : 

 si rut fed and unstra'ifed. 



Strut -/cation consists of the division of a rock 

 into regular parallel planes or leaves, varying in 

 thickness from that of thin paper, to several yards. 

 Strata are often tortuous and variable in thickness 

 in different parts of the same lamina or layer; 

 "nevertheless, the fundamental idea of stratification, 

 is that of parallelism in the layers." "The term 

 stratum is sometimes employed to designate the 

 whole mass of a rock, while its parallel subdivisions 

 are called beds, or layers." So also of sand, clay, 

 gravel, fee. 



The term led is used to designate a layer or mass 

 of rock more or less irregular, lenticular or wedo-e 



shaped, lying between the layers of another rock 



such as beds of coal, gypsum or iron. 

 Fig. 1. 



Without lamina. 

 With waved lamina. 

 Finely laminated. 

 Coarsely laminated. 

 Obliquely laminated. 

 Parallel lamina. 



" A seam is a thin layer of rock that separates 

 the beds or strata of another rock, as a seam of coal, 

 limestone, fee." 



A joint is a separation of rocks, both stratified 

 and unstratified, into masses of some determinate 

 shape : joints are more or less parallel, and usually 

 cross the beds obliquely. 



Cleavage planes are divisions in rocks, which do 

 not coincide with those of stratification, lamination 

 or joints. They are supposed to result from a crys- 

 taline arrangement of the particles of the rock. 

 Fig. 2. Cleavage Planes. 



d A A 



A A a B 



[Fig. -! exhibits the planes of stratification, B, B, — the 

 joints A, A, A, A, and the slaty cleavage, d, d. ] 



Horizontal strata are those which have little 01 

 00 inclination, but lie parallel with the horizon : this 

 position, however, is rare, almost all strata being 

 more or less inclined. 



Fig. 3. Horizontal Strata. 



winch they 



The dip of strata signifies the a 

 form with the horizon. 



Outcrop. — When strata are uncovered above the 

 surface, or protrude from the side of a hill so as to 

 be visible, they are said to crop out. 



Fig. 4. Dip and Outcrop. 



An escarpment is formed when strata terminate 

 abruptly, so as to form a precipice. 



A fault in a rock is the dislocation of strata, so 

 that their continuity is destroyed, and a series of 

 strata on one or both sides of the fracture are forced 

 from their original position, and raised one above 

 another, or, moved laterally. Faults are generally 

 filled with clay, sand and fragments of other rocks. 



A gorge is a wide and open fissure or fault : when 

 still wider, with sloping sides and rounded at the 

 bottom, it is called a valley. 



A dyke is a mass Fig. 5. A Dyke. 



or wall of rock inter- ^^m^^m^^^^m^m^ 

 posed between the |§| 

 ends of a disloca- 

 tion, so as to break 

 their continuity : — 

 dykes rarely send off 

 branches. 



Veins are portions of rock smaller than dykes, 

 proceeding from some large mass, and ramifying 

 through a rock of a different kind. Metallic veins 

 were originally melted metals, which were injected 

 into the fissures and crevices of rocks by some 

 subterranean force. 



Fossil. — This term includes those petrified re- 

 mains of plants and animals which are found in 

 alluvium, or imbedded in solid rock, and constituting 

 part of its structure. 



Formations. — The term formation is used to 

 designate a group of rocks having some character 

 in common — either in relation to age, origin or 

 composition. Every formation consists of several 

 varieties of rock, all agreeing in certain qualities, 

 and occupying such relative situations as to indicate 

 that they were formed during the same period and 

 under the same circumstances. Thus we speak of 

 graywacke formation, gneiss formation, coal for- 

 mation, fee. 



Wheat Flies. — We collected from a bin of wheat 

 a number of flies, on the 10th day of December, which 

 appeared to have recently hatched out in the same. 

 They are not the Cecidomyia trilici, nor the Hessian 

 fly, nor the wheat wcavil ; all of which we have col- 

 lected in Georgia. Wc know not what to call these 

 last. Some will be sent to Dr. Fitch, of Salem, 

 N. Y. A good deal of wheat has been sown in this 

 State within the last two months. Seed sent us from 

 Wheatland has come up well. Augusta, Ga., Dec. 



