GLACIAL DRIFT. 283 
He will shortly present the results of this examination, and color upon 
the map of Surface Geology their geographical positions. No feature 
of our drift moraines is so striking as this, and it is singular that pre- 
vious authors have almost universally overlooked or misunderstood it. 
The question has been put to us, As New Hampshire has not been 
submerged since the Helderberg period, and there may have been other 
periods of cold besides the one called par excellence the glacial drift, why 
do we not find moraine accumulations of the earlier ones? I think we 
have abundant evidence of a Triassic glacier in Massachusetts, formed 
of materials partly derived from New Hampshire. The stones of the 
Mt. Mettawampe conglomerate are too coarse to have been moved by 
water alone, and the stones have a glaciated appearance. As there 
seem to be no rocks in our state analogous to the Triassic conglomer- 
ates, we may say, with assurance, that if any glaciation occurred previous 
to the post-tertiary, it could not have antedated the New Red Sandstone. 
It seems probable that Tertiary glaciated beds would be characterized by 
features quickly discernible, and not easily confounded with anything 
else earlier or later. 
But certain beds are brought to our notice, which seem to antedate 
the lower till. The best known is represented in Fig.60. A railroad 
cut in South Lyndeborough, 
two miles west of the station, 
exhibits three layers in the till. 
The top is the familiar loose 
ferruginous earth, such as uni- 
Fig. 60.—SECTION IN TILL, LYNDEBOROUGH. 
versally covers the ground- a. Upper till; b. Lower till; c. Hardpan. 
moraine. Next, 4, is a good 
example of the lower till, full of glaciated pebbles, porphyritic and granitic 
gneisses, mica schist, etc., 5 feet, and in one case 6 feet long. The lam- 
inated appearance arising from compression is clearly defined. Beneath 
this is a coarser mass, reaching to the bottom of the cut, so very com- 
pact that a pick had no effect when struck into it by the workmen; only 
gunpowder or a stronger explosive could excavate it, and it was neces- 
sary that the holes should be bored horizontally near the surface to be- 
come effectual in removing the earth. There is nothing visible in the 
earth itself different from the lower till above it, save that the compo- 
