LETTERS TO A. GEIKIE 



roofing slates; it is a very fine glossy hydromica slate 

 (I suppose hydromicaceous from its microscopic charac- 

 ters; it has not yet been analyzed chemically). Then, 

 to the south, where fossils appear near Poughkeepsie and 

 the limestone is the same western belt of Taconic lime- 

 stone, both the limestone and the associated slate contain 

 Lower Silurian fossils. In our Taconic region we have 

 parallel belts of limestone and schist going east from 

 Canaan-Four-Corners, New York, we have. I do not in 

 the section undertake to give relative distance correctly 

 nor precise dips. 



[Here followed a pen diagram and notes.] 



" Now that eastern gneiss is not found anywhere to the 

 westward, each range of schist is in its place; the alterna- 

 tion is that of successive interstratified and interfolded 

 beds of limestone and schist; and the metamorphism 

 decreases in grade westward with remarkable regularity, 

 and not only in Berkshire, but all the way through the 

 southern half of Vermont, as well as to the south of 

 Berkshire. 



" I hope you are not intending to publish your con- 

 clusions ; indeed I cannot suppose this, as you know how 

 dangerous it is to work out geological problems with three 

 thousand miles between you and the region to be investi- 

 gated. After your very important paper on the Scottish 

 Highlands was republished in our Journal, I had occasion 

 to publish the first part of my article ' On Taconic Rocks 

 and Stratigraphy,' in vol. xxix., 1885, p. 205, giving 

 with it a map of the southern part of Berkshire and of 

 northeastern Connecticut; and in it I allude, on p. 442, 

 to the impossibility of the long overthrusts such as you 

 have in Scotland. I think I sent you a copy of this 

 paper. I shall publish the remaining part this season, 

 and will then send a copy of the whole together. 



(< Our Taconic limestone consists in Vermont and near 

 Poughkeepsie of limestones of Lower Silurian and Upper 

 Cambrian united in one mass, fossils of Upper Cam- 

 brian, calciferous, and Trenton occurring in it. After 

 reading this letter if you will then run over my article 

 just now referred to (in vol. xxix., p. 206), you will be 

 able to judge on the Taconic questions; but better still 

 after you have the remaining part of my paper. 



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