298 Scientific Geology. 



their decidedly fragmentary character, will not allow such a supposi- 

 tion to be indulged for a moment. It is impossible for a geologist to 

 mistake the evidence, which he sees at almost every step, that he is 

 passing from older to newer formations, just as soon as he begins to 

 cross the valley of Berkshire towards the west. We are driven then 

 to the alternative of supposing, either that there must be a deception 

 in the apparent outcrop of the newer rocks from beneath the older, or 

 that the whole series of strata has been actually thrown over, so as 

 to bring the newest rocks at the bottom. The latter supposition is so 

 improbable that I cannot at present admit it. But perhaps we may 

 explain the anomaly by supposing a deception in the case. It may 

 be that the relative position of the strata is as in the subjoined ideal 

 section. 



Gneiss and Mica Slate. 



In the greater part of the Hoosac range, the strata of gneiss and 

 mica slate are nearly perpendicular in their dip. As we descend that 

 mountain into the valley of Berkshire, we strike first a range of 

 quartz rock, whose stratification is very obscure, and which moreover 

 is much hidden by diluvium ; so that the junction between this rock 

 and the mica slate and gneiss of the Hoosac range, is rarely if ever 

 exhibited. As we proceed west, we find successive and sometimes 

 interlaminated strata of limestone, and mica slate ; whose con- 

 nection with the Hoosac range is no where presented, as nearly all 

 the larger streams of water and the vallies run in the direction of the 

 strata. Now may not the strata of Berkshire valley rest unconforma- 

 bly on the mica slate and gneiss of the Hoosac range? Certain it is 

 that the dip of the former, although in the same direction, is consid- 

 erably less than that of the latter. It may be, also, that another se- 

 ries of strata farther west, (ex. gr. the clay slate, transition limestone, 



