^24 



ON STRATIFICATION. 



3. Cotemporaneous veins, which in every theory 

 are supposed to have been formed at the same 

 time with the rock in which they are contained, 

 are to be observed passing through several different 

 strata or beds, as through granite and gneiss, or 

 through basalt, amygdaloid, wacke, and trap- tuff, 

 thus proving that these strata or beds are of simul- 

 taneous formation, or that no cessation of the pro- 

 cess of deposition took place after the formation 

 of each of the individual rocks. 



4. Beds of mountain rocks, as of granite in 

 gneiss, are so connected with the surrounding stra^ 

 ta, that we cannot hesitate in considering them as 

 illustrative of the simultaneous formation of strata 

 in general. Thus, these beds are sometimes of 

 considerable extent, and terminate in every direc- 

 tion in the rock in which they are situated, and 

 are so intermixed at their meeting or line of junc- 

 tion that it is difficult to say where the one begins 

 and the other ends. Here, it is evident, that the 

 granite of the lowest part of the bed is of co- 

 temporaneous formation with the immediately subr 

 jacent gneiss ; that the granite of the uppermost 

 part of the bed is of cotemporaneous formation 

 with the gneiss immediately above it , and that 

 the granite of the great portion of the bed has 

 been fprri)e4 at the same time with th^ bound- 

 ing gneiss. In other instances, these beds are 

 of great thicknesSj^ and send out from them veins 

 of granite in all directions into the surrounding 

 rock. 



