RANGE. 335 



red sandrock series at Rich's mills, is a whitish sandstone, intermediate, in lithological 

 character, between Potsdam sandstone and quartz rock. This sandstone is about twenty 

 feet thick, interstratified with coarse limestones, which possibly belong to the same series. 

 These beds of sandstone appear again at the village of Shoreham. A mile or two north of 

 the village the sandstone is thicker than at any locality southward of it. It closely resem- 

 bles Potsdam sandstone. The rocks north of the latter locality have a mongrel character, 

 being intermediate between sandstone and limestone. The most satisfactory ledge in the 

 northeast part of Shoreham, or the one which corresponds more nearly to the rocks of the 

 series under consideration, is upon the east bank of the Lemonfair River, at H. De Long's 

 house. It is a high bluff of gray calcareous sandrock, lying nearly horizontal, like the 

 west edge of the whole range of red sandrock. We have extended the color of the red 

 sandrock from the north upon the map, so as to cover all these ledges though with some 

 misgivings. 



But near Mr. C. Gale's house, upon the east line of the town of Bridport, appears a 

 great ledge of rocks, the continuation of the calcareous gray sandstone of Shoreham, 

 which no one can doubt belongs to the red sandrock series, as it possesses the characteris- 

 tic color and composition of the red sandstone. 



It is moreover the south end of the hill which gradually rises into the Snake Mountain 

 in Addison, the highest summit in the range from Bridport to Burlington. As one stands 

 upon the top of Snake Mountain, and views one after another the peaks with their sharp 

 points and steep western mural faces, he sees most distinctly their geological character. 

 Snake Mountain, Buck Mountain, Marsh Hill, Shell House Mountain, Mount Fuller, 

 Mount Philo, Glebe Hill, Pease Hill, and Mutton Hill, all belong to one great geological 

 sheet, that formerly extended much further westward towards those Laurentian rocks 

 forming such conspicuous mountains in New York ; and covering up the several success- 

 ive concentric bands of lower silurian rocks beneath. The tough sandstone has resisted 

 decomposition, and its ragged edges project pointedly to the west in proportion to the 

 compactness of the ledges and their comparative freedom from erosion ; while the softer 

 shales and limestones beneath have mostly disappeared, forming the valley of Lake 

 Champlain, as well as the foundations of the successive range of mountains we have just 

 mentioned. 



The east sides of these mountains slope gradually to the east because of the dip of the 

 rock. In Monkton, the range suddenly widens greatly. This is because the same rocks 

 are repeated in successive undulations, as instanced upon Fig. 240. A spur runs down 

 from the southeast corner, as seen upon the map, into the south part of New Haven, 

 and is interstratified there with the crystalline white Eolian limestone. In Chittenden 

 county the width of the sandstone diminishes greatly, being almost entirely cut off in 

 Shelburne. This narrow belt, however, is no thinner than the rest of the range. It is 

 reduced by erosion to as small a width as is possible, and there are no undulations in the 

 strata to increase its lateral dimensions. 



Prof. Thompson spent many years of his life upon this formation in Burlington, and 

 therefore we quote from his notes what he has said respecting this series of rocks in Chit- 

 tenden County : 



" The western border of this formation consists of an interrupted series of uplifts, vary- 



