318 SYLVA AMERICANA. 



constitutes the soil ; in other places it is barely sufficient to form 

 a coating to the strata, and in others it is entirely wanting. 

 Sometimes the strata are continued in a regular arrangement, 

 preserving the same inclination to a very considerable extent ; 

 but more commonly they appear in some parts separated, as if 

 they had been broken asunder. These separations are usually 

 in a perpendicular direction, and the cavities are found filled 

 with various heterogeneous matters. Sometimes these are chiefly 

 composed of fragments of the adjacent strata, but for the most 

 part they consist of mineral or metallic substances of a different 

 nature. When these fissures are filled with broken fragments 

 or rubble, as it is called, it very commonly happens that they 

 become the beds of brooks or rivers. When the fissure is filled 

 with a solid stony matter, this forms what is called a dyke. 

 If a mass of mineral or metallic matters fill the fissure, or be 

 insinated between the strata, it forms what is called a vein, and 

 these veins sometimes branch between the strata in various 

 directions. When a fracture has taken place in the stratified 

 mass, one part of the mass sometimes preserves the same position 

 as it had before, or still forms a continued line with the other 

 parts of the mass, or is parallel to it ; but more frequently one 

 part is thrown out of its original position, and becomes more 

 inclined to the horizon than before. Sometimes one side of the 

 mass is more depressed than the other ; at others the two parts 

 of the mass are so distributed as to incline, towards each other, 

 as if they had been broken upwards. When the edges of the 

 strata on each side of the fissure are thus divided and disarranged, 

 they are said by the miners to trap. If the country in which 

 the strata lie runs in a waving direction of hill and dale, the 

 strata usually preserves the same waving direction, keeping pretty 

 nearly parallel to each other. 



The general observation of all modern geologists proves, that 

 all these materials may be distributed under four general classes; 

 the first, supposed to be coeval with the world, and are called 

 primative, and consist chiefly of granite and marble, below which 

 man has not yet penetrated. The second series, called by the 

 Wernerians transition rocks, are of more recent formation, and 



