Both sides of this hill are sandstone and puddingstone, frequently alternating: though these are most extensive on the west side, and as we rise the puddingstone predominates. The strata dip to the east about 10 degrees. Near the centre of this range is a ridge of greenstone, with a mural face on the west, and amorphous masses lying at the base, half way up to its summit. This ridge does not rise so high as the puddingstone on the west of it, as may be seen in the view of strata with the map. It commences on the west bank of Connecticut river, about a mile north of the hill C, and increases in elevation nearly to the spot where it disappears at the fall of the river in Gill. This rock does not appear to rest on sandstone, but to descend through it, where there is an opportunity for observation. Deerfield river has worn a passage through the sandstone and greenstone 150 feet deep, and the greenstone passes under its bed, and the sandstone, at a few rods distant lies on each side of the greenstone. A similar fact has been noticed at the fall in Connecticut river, in Gill. Yet I have coloured this greenstone secondary on the map; for it is certain that Mount Tom rests on sandstone, and it is stated by Professor Silliman, that the same rock does in Connecticut. Could we penetrate deeper below the surface, it is probable the same would be found to be the case with this greenstone. As stated above, this rock disappears near the cataract in Gill, and it is succeeded by puddingstone. But four miles farther north, it again emerges in Bernardstone, though it rises but little above the surface. Here its character is changed. The hornblende is more crystalline, and the rock becomes decidedly primitive, as you approach a mountain of argillite and mica slate, into which it passes, and no greenstone has been observed north of this. It terminates not far from the line of Vermont. The red sandstone and conglomerate also terminate on the opposite side of the river in Northfield. The greenstone in the above described range, is of a finer texture than the same rock in Connecticut; and the feldspar, in some specimens, is scarcely discernible with a microscope. Indeed, in many instances, the eye would decide the rock to be basalt. Much of it is fissile, the laminæ varying from half an inch to a foot in thickness. This is most perceptible among the loose masses; but it exists also in that in place. Whether this circumstance be accidental, I will not attempt to decide.