1855.] on Trains of Erratic Blocks in Massachusetts. 91 



are seen with one or more flattened, smooth, striated, or furrowed 

 sides. They consist invariably, like the seven trains before men- 

 tioned, of kinds of rock only met with in the region lying to the 

 north-west. In one cutting, the drift below the main train No. 6 

 is 30 feet thick, and contains one or two angular blocks of the 

 green Canaan rock, of considerable, but not of the largest size. 

 There are no appearances here or elsewhere warranting the conclu- 

 sion that the trains owed their origin to the removal of an upper 

 portion of the covering of drift, the lighter materials having been 

 washed away, and the heavier made to stand out in relief. On the 

 contrary, the erratics of each train, whether large or small, look as 

 if they had dropped down over the linear spaces where they are 

 now strewed, on the surface of hill and valley, equally where the 

 drift is thickest, as where it is very thin or wanting. As a rule, 

 the drift contains no blocks of the first magnitude, although a 

 few occur, and some of the biggest are partially buried in drift, 

 showing that the transport of the heavier, and of a certain portion 

 of the lighter materials, was contemporaneous. 



Almost in every place where the removal of the superficial 

 detritus has exposed the underlying rock, a polished, striated, and 

 furrowed surface is seen, like that underneath the modern glaciers 

 of the Alps. The direction of the rectilinear furrows or grooves 

 has been proved by a multitude of observations, made by Professor 

 Hitchcock in this and other adjoining parts of Massachusetts and 

 New York, to be from N.W. to S.E, or similar to the course of the 

 large erratics.* The same geologist has pointed out that such 

 ridges as A B and C are smooth and furrowed, not only on their 

 tops, but sometimes 100 or 200 feet below, on their north-western 

 sides ; whereas, on their south-eastern declivities, if steep, there has 

 been no such action, although these also are grooved and polished 

 where their slope is gentle. The furrows, which are from an inch 

 to a foot in depth, usually cross the strike of the highly inclined 

 slates and slaty limestones at a considerable angle,, and in such 

 a manner as to demonstrate that the strata of the ridges A B and 

 C, and of the intervening valleys, bent as they are into a series 

 of anticlinal and synclinal folds, were already in their present 

 position, and had even suffered aqueous denudation before the drift 

 was thrown down upon them, and therefore long before the distri- 

 bution of the erratics above described had taken place. 



Although the trains, Nos. 5 and 6, are the most conspicuous, 

 several of the others are well defined, and contain limestone blocks 

 30 feet in diameter. Thus No. 7 was seen on the western flank of 

 the Leno\ range, and followed across the Richmond valley to the 

 eastern side of the ridge B, where the limestone, which has supplied 

 the travelled masses, is in situ. In like manner, Messrs. Hall 

 and Lyell observed, half a mile south of Pittsfield, enormous 



♦ ** Final Report on Geology of Massachusetts," p. 383, et seq. 1841. 



