720 THE JOURNAL OF GEOLOGY. 



In 1 864 James Hall and Sir William Logan T visited Mt. Wash- 

 ington and described it as probably synclinal in structure. 



The only investigator, however, who has made a detailed 

 study of the geological structure of the mountain is Professor J. 

 D. Dana, whose papers on the subject have appeared mainly in 

 the American Journal of Science. His first paper dealing with 

 the structure of Mt. Washington 2 appeared in October, 1873. It 

 contains a sketch-map with dip and strike observations. On page 

 38 he states : 



" Mt. Washington is a synclinal with limestone below and slate 

 above." • 



And on page 39 : 



"We thus find evidence of a very broad synclinal across the center of Mt. Wash- 

 ington. But just north, in Egremont, the structure is totally different ; the ridges S and 

 T 3 are the sources of very steep and comparatively narrow independent synclinals 

 with the axial plane inclined westward. * * * The synclinals S and T 

 become merged in one mass in Mt. Washington ; and as the limestone does not 

 appear at the smmmit, the intermediate anticlinal in the mountain was only an anti- 

 clinal of slate. In other words, the synclinal of limestone beneath the mass of the 

 mountain was one great trough with breaks and incipient flexures ; while to the north 

 these incipient flexures became two defined synclinals, with the intermediate anti- 

 clinal — the synclinals being courses in the ridges S and T and the anticlinal that of 

 the limestone outcropping between ; and then, farther north, there was formed the 

 Taconic synclinal T alone." 



In the same year there appeared in the Proceedings of the 

 American Association a paper entitled "The Slates of the 

 Taconic Mountains of the age of the Hudson River or Cincin- 

 nati Group. 4 In this paper Professor Dana states that limestone 

 dips west under slates along the east slope of Mt. Washington 

 for four miles, "that is, the whole eastern front." He describes 



1 Paper read by T. Sterry Hunt before the Natural History Society of Montreal, 

 October 24, 1864. Reviewed in the American Journal of Science, 2d ser., Vol. xl, p. 96 

 (1865). 



2 On the Quartzite, Limestone and Associated Rocks of the vicinity of Great Bar- 

 rington, Berkshire county, Mass., J. D. Dana, American Journal of Science, 3d ser., vol. 

 vi., p. 37. 



3 The ridge S is that of Mts. Darby, Sterling and Whitbeck, and the ridge T that 

 of Mts. Prospect and Fray near the New York-Massachusetts state line. (Cf. map pi. i). 



4 J. D. Dana, Proc. A. A. A. S., 22d (Portland) meeting, 1873, pp. 27-29. 



