124 GEOLOGY OF THE NAEEAGAJSTSETT BASIN. 



MAPS OF THE BOUNDARY OF THE BASIN. 



The progress in knowledge of the geology of this district is very well 

 represented by the delineation of the boundaries of the Carboniferous 

 formation on maps since the time of Maclure. In his map of 1817 this 

 field of rocks, then called "Transition," is represented as a triangular area, 

 with the base on the eastern shore of Narragansett Bay, between Providence 

 and Westport Harbor, and the apex at Boston. 



The first official surveys, those of Hitchcock in Massachusetts and 

 Jackson in Rhode Island, the final maps of which were published in 1841 

 and 1840, respectively, gave the boundaries as they have been commonly 

 represented on compiled maps up to the present time. Dr. C. T. Jackson's 

 map of 1840 represents the boundary in Rhode Island with much accu- 

 racy, but a strip of the more highly metamorphosed beds, in Cumberland 

 on the north and in Kingston, South Kingston, and the southern part 

 of Jamestown on the south, is included in his group of "primary rocks," 

 as are also the basal members of the Carboniferous along the Fall River 

 shore. 



Edward Hitchcock's map of 1841 gives the outlying boundary of the 

 Carboniferous with much fidelity, but the shoulder angles, probably due to 

 cross faults, along the northern border are not shown. Owing to his belief 

 in the Devonian age of the red strata in the northwestern part of the field, 

 an attempt was made to draw a line between these beds and the Coal 

 Measures. No attempt is made to show the inliers of granitic and other 

 rocks in North Attleboro and Namasket; indeed, they are nowhere described 

 by him. 



A later map, entitled Bristol and Rhode Island Coal Field, published 

 in 1853, 1 represents Devonian rocks as lying in a belt along the western 

 border of the basin from Cranston northward into the Norfolk County Basin, 

 and as sending out branches near Burnt Swamp Corner eastward along the 

 northern border of the main basin to Foxboro and westward toward Belling- 

 ham. The occurrence of the Carboniferous formation along the Fall River 

 shore is not yet recognized, nor are the outcrops of granite at Namasket 

 and North Attleboro. The same is true of the horseshoe fold of the red 

 rocks which occur in North Attleboro. 



'Massachusetts House Document No. 39, March, 1853. 



