902 



SCIENCE 



[N. S. Vol. XXIX. No. 753 



Tlie continuity of tlaese rocks over large 

 areas has been suggested and assumed rather 

 than proved. Notwithstanding this they form 

 a part of the same general problem, and any 

 assumption regarding the age of one portion 

 of this belt makes more imperative the need of 

 better establishing the principles that will 

 apply to the region as a whole. Any sugges- 

 tion of incorrectness in age of any part raises 

 the whole question to the fore. 



Great uncertainty prevails in the minds of 

 the Connecticut geologists as to the age of 

 the greatly injected, disturbed and altered 

 schists and limestones in the western part of 

 that state. Manifestly any reasonable inter- 

 rogation regarding the generally assumed age 

 of the limestones and schists of southeastern 

 New York is of great interest. The recent 

 conservative suggestion of Berkey that the In- 

 wood limestone and Manhattan schist are of 

 pre-Cambric age is a case in point. 



The work of Hitchcock and Emerson in 

 Massachusetts, that of Percival, Dana and 

 the Connecticut Survey in Connecticut, and 

 that of Mather, Dana, Merrill and Berkey in 

 New York has done much to unravel the com- 

 plicated geology of this region ; but much con- 

 fessedly awaits solution. The problem is to 

 a great extent a structural one and is com- 

 plicated through metamorphism by igneous 

 intrusion. 



Limestones are known in the pre-Cambric 

 rocks of Massachusetts, southeastern New York 

 and New Jersey in the proximity of lime- 

 stones of younger age. The uncertainty is 

 not at this point, but as to which is which. 

 The work of Cook, Britton, Nason and Bay- 

 ley does not leave us clear as to what is 

 assignable to the pre-Cambric and what to 

 the Paleozoic in the Highlands of New 

 Jersey. The New York geologists are work- 

 ing at this problem, and the New England 

 geologists will doubtless take the subject up 

 again in the near future. 



Much doubtless depends upon the success 

 we may attain in correlating areas with one 

 another as well as in establishing principles 

 that will fit them all, and to what extent such 

 a thesis as may be drawn up can be supported 



by actual evidence, or reasonable inference, or 

 both. With these general principles our inter- 

 pretations of specific phenomena must fit if 

 the principles are to stand. 

 The Geology of Dutchess County, New York^ 



The study of these problems reasonably be- 

 gins with the examination of the least altered 

 strata of the Hudson Valley. These strata, 

 showing continuously increasing metamor- 

 phism as they are traced eastward, are well 

 displayed in Dutchess County. Eield work in 

 this county reveals that the metamorphism ap- 

 proaches the character of a function of the 

 distance of the strata from the Hudson River. 

 The increment by which the metamorphism 

 approaches a given degree varies in value, but 

 apparently always is greater per unit distance 

 as one approaches the southern part of the 

 county. The fact that the pre-Cambric rocks 

 cut through the southeastern and southern por- 

 tion of the county indicates that the degree 

 of metamorphism may, in a measure, be 

 directly connected with the proximity of the 

 Highland mass. 



The accompanying generalized sketch map 

 is not intended to show the details of the 

 areal geology of southeastern New York but 

 rather to show pictorially the character of 

 the general problem. It is based upon per- 

 sonal work in Dutchess County, particularly 

 in the Poughkeepsie quadrangle, and upon 

 the maps of Dana, Smock, Merrill and Berkey. 



The north and south continuity of the 

 western limestone belt (Barnegate or Wap- 

 pinger) of Dutchess County was shown by 

 W. B. Dwight. The identity of the eastern 

 so-called Millerton-Eislikill belt with the 

 Wappinger was proved for its northern or 

 Millerton portion by the same worker. Re- 

 cent work by the writer in the southern por- 

 tion of the eastern belt, the Fishkill lime- 

 stone, shows conclusively by the discoveries 

 of fossils the presence of Georgian and Beek- 

 mantown terranes within this formation. 



While considerably more metamorphosed 

 than the Wappinger the alteration of the 

 eastern limestone has not obliterated the 



' Published with the consent of the New York 

 State Geologist. 



