THE MOUNT TOBY OONGLOMKUATE. 3G1 



Great ledges of tlie coarse rock stretch away south and have I he 

 abnormal attitude, strike N. (30° W., dip 3()° N., thus making' the existence 

 of a fault here the more prol)able. This is just the ])osition of the main 

 east fault at the foot of the east scarp of the valley. 



The exact contact of the two rocks may be seen in the bed of the 

 brook which crosses the readjust south of the village (south of J. llolmaii's), 

 by following the brook east to the foot of the scarp. Here, resting on the 

 black crushed and silicified schist, is a compact pudding-stone with abun- 

 dant pebbles, about 4 inches long, of the schist in a gi'ound of deep-red 

 sandstone. We have here the combination of finer far-traveled and coarser 

 local material, discussed more in detail below (p. 374). From this point 

 heavy kame gravels cover all the shore deposits far into Connecticut. 



THE OUTCROPS OF CRYSTALLINE ROCKS IN THE MIUST OF THE MOUNT TOISY 



CONGLOMERATES. 



The Conwaij hornblende- (unl quarto-schists at Whit mores Fcrri/, in. Sniider- 

 land. — I had long maintained that the conglomerate of Mount Toby could 

 not be above 1,000 feet thick, and that it must have a base about 300 feet 

 above the river, so that the discovery of large outcrops of the imderlying 

 masses in the heart of the Mount Toby conglomerates was very gratifying 

 to me. It has proved very useful, as well in throwing light upon the dis- 

 tribution of the older rocks l)eueath the Trias as in accounting for the 

 source of the materials of a large portion of the couglonierates and the 

 extreme coarseness of those conglomerates at large distance from the old 

 shore bluffs, which seemed to be the only source for them. Several of the 

 rocks outcropping thus are unique and their presence in abundance in the 

 conglomerate had long been a puzzle to me. Again, at certain points in 

 the mountain far from the shore, the pebbles of the conglomerate swell 

 suddenly to large size and maintain such size for a limited area around the 

 central point. This has now enabled me to locate several outcrops of 

 crvstallines in the midst of the clastic rocks. 



The first area discovered was the more interesting, as it forms the 

 whole or part of the ledges over which the waters of the mill at Whitmores 

 Ferry run, east of the road, while west of the road they pass over the black 

 fish-bearing, shaly sandstones. The crystalline rock is hei'e a black, fine- 

 grained and thin-bedded amphibolite, and that it has not been recognized 

 as distinct from the black fish-bearing sandstone is not surprising. Upon 



