HOOSAC MOUNTAIN. 105 



Jersey iron ores) 10° to 15° to the north. It is this pitch which enables us 

 to get the series of rocks in normal position and measure their thickness, 

 just on the axis of the fold, for on the sides we could never have known 

 which rock was the upper or the lower, owing to inversions, or whether the 

 apparent thickness was not produced by duplication of a thin layer by 

 frequent closed and overturned folds, as is the case at the southern end of 

 the field. 



This anticline preserves the rocks in their normal position on the east 

 side, but on the west they are folded under in inverse position, with eastern 

 dip. (See Profile v", PI. vi). It is also proved that at the south end the 

 rocks have been pushed in under, so that they dip north instead of south, as 

 they would naturally do if the fold terminated in another dome at its south 

 end. Where the normal east side of the anticline and the underturned west 

 and south sides meet we find a great crumpling, and then the two sides 

 come together and the whole series strikes north to south. The long, thin 

 tongue of schist which runs south from the main mass is conformable to the 

 gneisses on both sides of it, and must therefore lie in a narrow trough in the 

 white gneisses which terminates at the south end. The second or west band 

 of gneisses, judging from its conformity to the schist and from the fact that it 

 runs into the larger area of gneiss as one of the series, after the schist tongue 

 ends, must be considered identical with the gneiss next to the granitoid 

 gneiss, except that in this western band it lias more of the quartzite ami 

 less of the gneiss character, corresponding to the general change across 

 this meridian. This western band would in that case represent an over- 

 turned anticline in the white gneiss, really overlain by the limestone, 

 which by the overturn is made to dip under it. This anticlinal trough 

 of white gneiss pitches under the schist north of the tunnel. Lastly, if 

 the limestone and schist are the same rock we must suppose that the 

 change from one to the other took place in the eroded portion of the 

 arch which connected the limestone with the trough of schist. Profile 

 v a , PI. vi, illustrates this theory. I am well aware that such an explan- 

 ation seems forced. It would be much more plausible to say that these 

 formations are separated by north to south faults, but all the evidence goes 

 against the existence of faults. Where formations are found to overlie each 



