CONANICUT ISLAND. 233 



are darker in color, usually dark blue, often almost black, but not of the 

 dense black hue characteristic of the shales often called coaly in this paper, 

 in which fossil ferns are usually present, These shades of color are also 

 found where they are not due to A^ariations of moisture, but in general the 

 dark-blue type prevails, excepting in the more weathered portions. Dark 

 color banding not infrequently indicates the true dip and strike. While the 

 general strike is undoubtedly northerly, the dip is not so easy to determine. 

 While the writer believes that the series of shales as a whole overlies 

 the series of sandstones, conglomerates, and coaly shales already described, 

 and while an easterly dip would best accord with such belief, it is only 

 proper to mention that the time at his disposal did not enable him to make 

 a satisfactory study of the problem. The dips on the western side of the 

 shale series were often found to be very steep, almost vertical, and in some 

 very large exposures more or less steep westward, while on the eastern 

 side, as far as the northern part of Mackerel Cove, the dips were less vertical 

 and were often eastward. The chief reason for believing that the Conanicut 

 shales are above the Kingstown sandstone conglomerate and coaly shale 

 series is their occurrence east of the latter, especially east of Fox Hill, and 

 the uniform eastward dips of the latter series, especially at Fox Hill, but 

 also on Dutch Island. Unfortunately, the uniform east dip along the western 

 margin of northern Conanicut is not continued in an equally apparent man- 

 ner in the more crumpled and folded series on the eastern side of the island. 



GRANITE AREA, THE DUMPLINGS, AND ARKOSE REGION WEST OF THE DUMPLINGS. 



Coarse granite, in part filled with large johenocrysts of orthoclase, occu- 

 pies the southern end of the northeastern half of Conanicut, from the 

 southern side of Bulls Point to Mackerel Cove. North of the granite, on 

 the Mackerel Cove side, is a considerable exposure of arkose. Near the 

 granite the arkose contains some of the large phenocrysts of orthoclase 

 derived from the granite, scarcely broken up. Farther from the granite the 

 large phenocrysts are more rare. Interbedded with the arkose are more 

 carbonaceous, sandy, and shaly layers, with strike about N. 70° E. near 

 the granite. The arkose is exposed along Mackerel Cove as far as a little 

 stream entering the cove from the east. North of the mouth of this stream 

 only the Conanicut shale series is exposed. The color banding of this shale 



