No. 2. — On the Geology of the Cambrian District of Bristol County, 

 Massachusetts. By N. S. Shaler. 



[Published by Permission of the Director of the U. S. Geological Survey.] 



Preliminary Note. 



For a number of years I have been engaged in an incidental manner 

 in studying the geological structure of the great synclinal district to 

 which I have given the name of "the Xarragansett Basin." This 

 geological field, extending from the southern part of Narragansett Bay 

 in Rhode Island to the region of the granitic hills which includes the 

 Blue and Sharon Hills of Massachusetts, and eastwardly to the region 

 occupied by the town of Hanover in Massachusetts, is mainly under- 

 laid, as is well known, by rocks of Carboniferous age. My principal aim 

 has been to determine the geological history of this Carboniferous sec- 

 tion. Incidentally, it has been necessary to make some study of the 

 deposits which lie below the level of the Millstone Grit. In these latter 

 inquiries I found it necessary to do a good deal of work on the exten- 

 sive series of more or less metamorphosed ancient rocks which lie be- 

 tween the western border of Rhode Island and the western edge of the 

 Coal Measures, from Greenwich, R. I., to Wrentham, Mass. This 

 inquiry, although incomplete, has developed certain facts of consider- 

 able interest, which it appears to me should be made public before the 

 preparation of my final report on the Narragansett Basin, which can- 

 not be finished for some time to come. The most interesting of the 

 many results which I have obtained in this Pre-Carboniferous series 

 of rocks consists in the discovery of an extensive series of Cambrian 

 deposits, containing a tolerably abundant and fairly determinable set of 

 fossils. The discovery of these beds not only enables us to fix the age 

 of an extended section of rocks, but to ascertain a number of facts 

 which have a great importance with reference to the general history of 

 this portion of the continent. 



Several geologists have observed the fact that between Providence, 

 R. I., and Wrentham, in Massachusetts, we have an extensive develop- 



VOL XVI. — NO. 2. 



