In Mount Toby, in Sunderland, is a cave nearly 150 feet above the bed of Connecticut river. It opens to the north and west, forming a quarter of a circle, is 130 feet in extent, 60 feet deep, and from 3 to 20 wide. A little to the south of it, is a fissure in the puddingstone, formed by a separation of the rock, ten feet wide, and as deep as the cave. So perfect is this division, that it appears as if cloven down by the sword of some Titan. Perhaps this cave and fissure were formed by the washing of the waters of the lake we have mentioned on the sandstone and conglomerate beneath; thus causing the superincumbent rock to fall and separate. There is no appearance of any other convulsion. Imperfect, calcareous stalactites are found in this cave. The falls in Connecticut river, at E, are not unworthy of notice. The river here is about 40 rods wide, and the height of the main cataract, raised considerably by an artificial dam, is 30 feet. The fall continues two miles. On the north bank you view the cataract from elevated ground, and can see the river nearly a mile above and below--above, perfectly smooth and calm, below, forming a quarter of a circle, and tumbling among the broken rocks. On the opposite side of the river are a few buildings, the commencement of a canal, and, behind these, moderately elevated hills, covered with woods. Two rocky islands near the middle of the descending sheet, and another thirty rods below, add much to the beauty of the view. Looking from the southeast shore, you have a partial prospect of the falls, and a view of an amphitheatre of greenstone hills, through which a small river empties. The pleasure derived from the view proceeds more from its wildness than its sublimity. The position of the hills, boundaries, and rivers, on the accompanying map, may not, in all cases, be precisely correct. The general outlines were enlarged by a pentegraph from Carleton's map of Massachusetts, and the intermediate objects were placed chiefly by the eye; their relative situations being determined by travelling over the ground, and viewing them from different elevations. The boundaries of the several formations have not been so carefully noticed near the angles of the map as in the central parts. Of their correctness generally, however, I am confident. The latitude and longitude of Deerfield, from which those on the map were marked, were obtained by taking a mean of the observations given by Gen. E. Hoyt, in the Transactions of the American Academy of Arts and Sciences, and of twelve lunar observations since made. The result is, Lat. 42° 32' 32". Long. 72° 39' from Greenwich.