26 BULLETIN OF THE 
been worn down to something like the form in which they now appear. 
If we are ever able to determine the age of the Roxbury conglomerate, 
we can place the period of the extrusion of some of these hornblendic 
granites in a yet more accurate manner, for it is evident that. those 
of the Blue Hill region, as before remarked, were subjected to erosion 
before the deposition of those conglomerates. 
The foregoing account of the Cambrian localities of the Attleborough 
district will, it is hoped, be sufficient to attract the attention of geolo- 
gists to this important district. Although this report is in its nature 
preliminary, enough has been set forth to show the importance of the 
field with reference to many problems in American geology. 
