1855.] on Trains of Erratic Blocks in Massachusetts. 95 



It has been objected to the theory of submergence that the great 

 train, No. 6, has climbed a part of the ridge B, higher than its 

 supposed starting point in A. But there are no exact barometrical 

 or trigonometrical data for this assertion. Messrs. Hall and Lyell 

 could only estimate roughly the relative heights of the knob d in A, 

 and that of the pass between k and / in B, by means of a spirit- 

 level, as they stood on the Canaan knob. It appeared to them that 

 the gap in B, or the ravine between Merriman's Mount and Flat 

 Kock, is 50 or 100 feet below the highest crest of A, in which case 

 the objection falls to the ground. Some of the erratics of No. 6, 

 in the Richmond valley, have probably come from an elevated 

 point in Merriman's Mount, and therefore present no difficulty, 

 since that mount consists of the green chloritic rock, but others 

 have come from the Canaan ridge, and have crossed the ridge B, as 

 before stated. If it could be shown that some of these stones 

 repose on B, at points actually higher than the crest of A, the fact 

 would be important, but by no means inexplicable by the glacial 

 theory. Mr. C. Darwin has shown, that during the gradual subsi- 

 dence and submergence of a coast situated in high latitudes, packed 

 ice with stones frozen into it is continually driven up on ^tlie sea- 

 beach above high-water mark, and if the land be going down at the 

 rate of a few inches in a year, the boulders, by being simply kept 

 up to the sea level, will slowly climb up the hills higher and higher, 

 so that a ridge after sinking may, when it re-emerges, have stones 

 lodged upon it at levels above those of the lands from which the 

 same stones were derived.* 



The drift of Berkshire and of New England in general has a 

 great resemblance to the terminal moraines of glaciers, being un- 

 stratified and containing fragments of rock, some angular, others 

 rounded. But the proportion of rounded boulders is far more 

 considerable in the drift than in an ordinary glacier moraine, in 

 which last, as Mr. D. Sharp has lately shown in reference to 

 some Swiss glaciers, the rounded blocks are quite the exception 

 to the rule. Want of stratification is the natural result of the 

 melting of matter out of stationary ice, the light particles and the 

 heavy stones dropping down together, and no current of water 

 sorting the materials, and carrying those of less specific gravity to 

 greater distances. Stones frozen into coast-ice may have been 

 rounded, some by rivers, others by the waves of the sea. The 

 dearth of marine shells is sometimes urged as an argument against 

 the hypothesis of submergence beneath the sea, and it is certainly 

 strange that marine shells should be so rare in drift. They are, 

 however, extremely scarce in parts of New P^ngland, such as Ver- 

 mont and Maine, where a few, nevertheless, do occasionally occur ; and 

 this holds good in Canada, as also in Ireland and other parts of the 

 North of Europe. As we cannot doubt that the formation accu- 



* C. Darwin, Gcol. Quart. Joum. Vol. VI., p. 315. 1848. 

 Vol. II. H 



