32 On Bowlders aad Rolled Stones. 
westerly part of sgtau where we leave the apparent 
course of the ocean current, and pass over rising ground 
tothe head waters of a ‘roel ae of Black River, where 
there is a great deposit of Breecia both in place and in 
loose blocks, some of the pieces of which are partially 
rounded. The little fragments of the rock are very white, 
and their angles almost invariably quite perfect, and what 
pera is singular, they are cemented by granite;* the 
rocks alternate with each other in place, a fact which 
Peis seen sometimes in the rounded rocks. As you de- 
-scend the stream and valley, they are plainly more ie more 
rounded, and at Black River, about four miles, there is 
hardly a rock of any other kind ; ; some are of many tons 
weight, and from that down to smail gravel, and even the 
sand and gravel of remaining hills or ridges, sixty or sev- 
enty feet high, are composed almost entirely of this kind of 
rock. The rivulet that descends into this valley is but a 
small mill stream at its junction with Black River in Ando- 
ver, and never could have had any agency in Sar oy 
i ns of 
seal and rounded rocks continue of the same find, 
re then begin to diminish, and the fine gravel and sand 
soon disappear, but the rounded rocks are seen more or less 
every where on the ground and in the banks. In passing 
over Salisbury Hills, from five to ten miles below (which 
are from one to two hundred feet higher than Black River) 
these rocks well rounded at first, compose nearly one half 
of the stone fences, and are every where seen in the Hills 
although sensibly and gradually lessening in proportion to. 
other rocks, so that before geRTIOg Salisbury, the stone walls 
are composed of only about ! or } of them. Quitting these 
hills, the traveller descends to the extensive plain of sand in 
Boscawen and Concord where few rocks are to be seen, 
and those are generally granite. After leaving these plains i in 
Pembroke, on the opposite side of Merrimack River, we still 
find rounded rocks of the same kind, but so few that only one 
occurs in two or three rods of stone wall, this is about thirty 
miles from their original situation. In taking here the London- 
Py Perhaps by a re- -aggregation ofits constituent minerals, quartz, feldspar 
