324 MYRON L. FULLER 



the north. There are a few pebbles of a fresher, though still 

 distinctly weathered granite dispersed sparingly in the till. The 

 difference in the extent of the decay is probably to be explain- 

 ed by the fact that the process which subsequently brought 

 about disintegration were, in the larger portion of the material, 

 well under way at the time of the ice advance, though actual 

 disintegration may not have taken place until long afterwards. 

 The fresher fragments were probably derived from portions of 

 the ledges from which the more highly decomposed material 

 had previously been removed. The thickness of the lower till 

 as exposed in the gravel pit is about four or five feet. The 

 color of the till is slightly darker than the overlying buff till, 

 but the distinction is not marked. 



The upper till is composed of a heterogenous mass of mate- 

 rial in which the same pink granite predominates, but with a con- 

 siderable intermixture of foreign material. Its line of demar- 

 cation from the lower till is well defined, but, as would be 

 expected from the fact that granite is the predominating material 

 in both cases, is not so sharp as in the first two of the Brockton 

 tills. All fragments of the upper till are fresh and usually present 

 well glaciated surfaces. 



PINE STREET EXPOSURE, STOUGHTON 



The gravel pit in which was found the last of the tills to be 

 described is located on the south side of Pine street at its 

 junction with Pleasant street near the northern boundary of the 

 town (Fig. 2, Exposure 5). The cut was about fifteen feet 

 deep at the time it was seen by the writer. Two tills were dis- 

 tinctly exposed in the section, the relations of which are shown 

 in Fig. 5. 



The lower till, as in every case which has been described, is 

 very homogeneous in composition. In this instance it is com- 

 posed largely of the disintegrated material of a biotitic and 

 hornblendic syenite, the source of which is probably close at 

 hand. There is a slight admixture of foreign material but 

 probably not more than 5 per cent. As in the case of the Ames 



