Tilton.] 502 [April 17, 
Gkxekal Character of the Rocks. 
The rock in the general area surrounding this part of tlie 
basin is a hornblende granite, but close to the basin area the 
rock is generally a felsite. 
Within the basin one rock is a conglomerate, the pebbles 
of which are quartz, subangular in shape, the larger ones about 
six inches long. AVith these quartz pebbles may be found a few 
granite pebbles, and, now and then, pebbles of diabase or dark 
felsite. The localities where this conglomerate is to, be found are 
four in number : at Sabrina Lake, north of South Natick, north- 
east of Farm Pond in a large hill, and southeast of Farm Pond 
in a less conspicuous ledge. 
The conglomerate outcrops close to Sabrina Lake are coarse as 
above described ; but in the outcrops found a little to the east- 
ward the conglomerate rapidly becomes much finer in composi- 
tion, indicating a deposit a little further from shore. 
There seems to be a transition from the conglomerate near 
Sabrina Lake through that north of South Xatick to the volcanic 
breccia near Morseville. 
A second rock in the basin area is an arkose rock found east 
of Farm Pond. The irregular angular granite fragments of 
which this rock is composed are not to be distinguished without 
a microscope. 
The third rock is a volcanic breccia extending east and west 
through South ISlatick. 
Discussion's of Special Parts of the Bouxdary betwekx 
Granite A3fD Basix Rocks. 
Proceeding from South Xatick in a southwesterly direction, 
the volcanic breccia first claims attention. It extends in a 
curved line west and southwest to half a mile west of MorsevUle. 
It lies adjacent to the conglomerate northwest of South Natick, 
and north of Morseville. It also lies next to the granite south of 
South Natick. 
One outcrop half a mile southeast of Morseville deserves special 
attention, as in this vicinity the T)reccia appears tufaceous. 
