1886.] 325 [Crosby and Barton. 



ON THE GREAT DIKES AT PARADISE, NEAR NEWPORT. 



BY W. O. CROSBY AND G. H. BARTON. 



The locality near Newport known as Paradise is about two miles 

 east of the city, and one-fourth mile north of Sachuest Beach and 

 the chasm called Purgatory. 



Mr. Dale 1 well describes it as "covering about one square mile, 

 and consisting of a series of more or less parallel, north-south, 

 rocky, precipitous or rolling ridges and hillocks of varying alti- 

 tude, the highest measuring from 80 to 173 feet above the sea. The 

 sides of several of these ridges are covered with their debris, the 

 intervening spaces are sprinkled with boulders, and the whole tract 

 bears evidence of the destructive element in geological history. 

 The name Hanging Rocks is applied to the easternmost elevated 

 ridge." 



Probably few localities in New England have proved more puz- 

 zling to geologists ; but we are confident that misapprehension of 

 the nature of some of the rocks has caused the structure to be re- 

 garded as much more complex than it really is. All observers have 

 detected an intimate relation between the topography and geology 

 of this district. President Hitchcock 2 and Prof C. H. Hitchcock 3 

 have recognized three principal north-south ridges, the most east- 

 erly of which is the Hanging Rocks ; but Mr. Dale describes the 

 topography more accurately as "comprising four high and three low 

 ridges, all trending N.N.E., but in places somewhat curved, in 

 others coalescing to form a lesser number of ridges." For the de- 

 tails of the topography, with the accompanying map and contours, 

 as well as for a full bibliography of the geology of Paradise, the 

 reader is referred to Mr. Dale's paper, 4 which is entitled to rank 

 among the most valuable contributions to the geology of Rhode 

 Island. 



The ridges of Paradise, with the intervening valle}^, are composed 

 of three kinds of rock: (1). The extremely coarse quartzite con- 

 glomerate, which is so well developed in the Hanging Rocks and 

 in the cliffs at Purgatory, and the metamorphism of which was so 

 ably investigated by the elder Hitchcock. 5 This wonderful rock 



1 Proc. Bost. Soc. Nat. History, xxn, p. 184. 2 Geol. of Mass., p. 535. 



sGeol. of the Island of Aquidneck, p. 113. 4 Proc. Bost. Soc. Nat. Hist., XXII, 179-201. 

 5 Am. Jour. Sci., 2d Series, xxi. 



