208 



GEOLOGY OF THE NARBAGANSETT BASIN. 



across the northwestern part of the Taunton quadrangle, through Norton, 

 in the vicinity of Providence, and along- the lower course of the Warren 



Fig. 29.— Case where a boring is the most economical and certain method of deter 

 coal beds in a given thickness of coal measures. 



presence of a series of 



River in Swansea. In areas of vertical strata, trenching across the upturned 

 edges of the beds would better serve the purpose. (See figs. 29 and 30.) 



THICKNESS OF THE CARBONIFEROUS. 



There are but few cross sections of the strata obtainable in the Narra- 

 gansett Basin which are so far free from the perplexing hindrances set forth 

 in the introduction to this report that the geologist can with confidence 



Fig. 30. — Case where a boring may miss an important coal bed and is not likely to discover more than one, and 

 where a trench at right angles to the strike would reveal the true number of seams of coal. 



give an estimate of the thickness of the beds entering into them. The 

 most satisfactory line of section in the northern part of the basin passes 

 from the southern margin through the Dighton-Swansea and Great Meadow 

 Hill or Taunton synclines toward Mansfield and the northern border. The 

 general relations of the structure along this line are shown in fig'. 8 (p. 122). 

 Measurements along this line give about 12,000 feet as the thickness of the 



