7() GREEN MOUNTAINS OF MASSACHUSETTS. 



of passing trains are also considerable. Moreover, that part of the tun- 

 nel which would have afforded the most important contact for determining 

 the relations of the Stockbridge limestone to the Hoosac mountain rocks is 

 entirely bricked over; it lies in the decomposed rock which caused so much 

 trouble during the building of the tunnel. Therefore, while the general 

 distribution of the rocks is easily found in the tunnel, much less was done 

 in the way of determining relations by contact than would have been possi- 

 ble under more favorable conditions. 



In the following description the reader is referred to Profile in, PI. v. 



Starting at the west end of the tunnel we find the Stockbridge lime- 

 stone of Hoosic valley in the long open cut which leads to the tunnel 

 mouth, and passing under the masonry of the portal; the dip alternates in 

 a series of small folds, sometimes east, sometimes west. From the portal 

 for 2,700 feet the tunnel is bricked, but at several of the manholes we find 

 rock in place. At a little over 1,600 feet we find in a manhole the first 

 occurrence of the fine-grained variety of gneiss with small porphyritic feld- 

 spars, and the same rock again at about 1,900 feet in. Near 2,000 feet the 

 albite-schist (Hoosac schist) is found in all of the manholes to about 3,800 

 feet. Then by transitional rocks this passes into the white gneisses which 

 extend to 0,001) feet, where by gradual transition they pass into the coarse 

 granitoid gneiss; this rock runs as far as 10,500 feet, then after 250 feet of 

 bricking the conglomerate-gneiss is found at 10,770 feet, and this extends 

 to 12,100 feet, where the albite-schist series is found in conformable con- 

 tact with the conglomerate-gneiss. The albite-schist, succeeded by the 

 Rowe schist, is then found through the rest of the tunnel. We find then 

 in the tunnel, going in from the west: first the limestone, which extends 

 into the tunnel proper a short distance, but is now entirely bricked in; 

 then the fine grained, banded, white gneiss (Vermont formation), extending 

 to about 2,000 feet from the portal; then the albite-schist for 1,750 feet; 

 next the white gneiss (conglomerate-gneiss) series (Vermont) for a little 

 over 2,000 feet; then the granitoid gneiss (Stamford gneiss) for a little over 

 4,000 feet; then white gneiss-conglomerate for 1,500 feet; and the schist 

 formation (Hoosac schist overlaid by Rowe schist) for the rest of the way, 

 or about 12,900 feet, of which the last 6,000 is occupied l>v the greenish 

 sericitic or chloritic Rowe schist. 



