232 CD. Walcott — The Taconic System of Emmons. 



formations by paleontologic evidence, was also imperative, as 

 their lithologic characters were of little comparative value out- 

 side of the Taconic area owing to local differences in the orig- 

 inal sedimentation and to the subsequent alteration of the strata 

 by metamorphic ageucies. 



With the assent of the Director of the Geological Survey I be- 

 gan field work during the season of 1886 and continued it until 

 the close of the field season of 1887. A few of the results of this 

 work were given in a paper entitled " Geologic Age of the 

 Lowest Formations of Emmons's Taconic System," and read 

 before the Philosophical Society of Washington, January loth, 

 1887, a brief abstract of which was published (this Journal, 

 vol. xxxiii, p. 153, 1887). On the 22d of April, 1887, I 

 read a paper before the National Academy of Sciences, at 

 Washington, bearing the title : "' The Taconic System of 

 Emmons." In it were given the results of my studies up to 

 that date ; and I exhibited a geologic map, and a cross-section, 

 of the Taconic area. As I was soon to return to the field this 

 last mentioned paper was not published.* 



Previous to studying the geology of the Taconic area I 

 worked during portions of the field seasons of 1883-4 on the 

 " Upper Taconic " strata of Northern Vermont and published 

 a part of the results in the introduction to Bulletin Thirty®of 

 the U. S. Geol. Survey, 1886. 



GEOLOGY OF- THE TACONIC AREA AS KNOWN AT THE PRESENT 



TIME. 



The section (see map)f crossing the Taconic area shows the 

 general position and relation of the strata, and their geographic 

 distribution is given on the map. In a report on the geology 

 of Washington County, ]ST. Y., I shall describe the geologic 

 section in detail. For the present purpose, however, the 

 section and map, supplemented by notes on the geologic for- 

 mations, will I think give the data required for a clear under- 

 standing of the geologic terranes. Beginning on the east, the 

 terranes will be mentioned in the order they are met with in 

 passing westward from the pre-Cambrian crystalline gneisses of 

 the Green Mountains to the Hudson River, and each will be 

 given a number by which to identify it in subsequent referen- 

 ces. 



One of the best localities to see the contact between the pre- 

 Cambrian crystalline gneiss and the overlying, bedded quartzite 



* A short abstract of it was sent, June 8th, 1887, to Professor N. H. Wincbell, 

 reporter on the lower Paleozoic rocks to the American Committee of the Interna- 

 tional Congress of Geologists, and was subsequently withdrawn owing to the 

 field work of the season of 1 887 having negatived and rendered obsolete several 

 of the conclusions therein expressed. 



f To be inserted with the second part of this paper. 



