94 



SCIENCE. 



[N. S. Vol. XII. No. 290. 



witli their flat dips and close resemblance 

 to the familiar sections in the Paleozoic or 

 other well-defined sediments, have borne 

 home to the writer with greater force than 

 have any others observed in the eastern 

 mountains the general conception of what 

 the ancient sediments must once have been, 

 before metamorphism, igneous intrusions 

 and upheavals threw them out of their 

 simple and regular relations. They show 

 that despite the severity of the changes 

 elsewhere displayed, two remnants remain, 

 not appreciably mashed, and scarcely even 

 tilted, and one can well picture to oneself 

 a regular and widespread sedimentary series 

 covering extended areas in this region. 



The Styles Brooh Section in Southern Jay. — 

 One more section will sufiSce. It is located 

 five miles from the last and beyond a group 

 of mountains. It runs in a northeast and 

 southwest line across a beautiful valley, 

 about two miles wide. In the bottom of 

 the valley, and fortunately cleared of a 

 heavy mantle of overlying drift by a recent 

 freshet, about 50 feet of graphitic quarzites 

 and gneisses with a northerly dip of 35 de- 

 grees are exposed. To the northeast, within 

 an eighth of a mile, a huge flow of basic 

 gabbro cuts out the sediments. To the 

 southwest, after three-quarters of a mile of 

 drift, there are rusty hornblendic gneisses, 

 which dip almost the same as the previously 

 mentioned ledge of quartzite ; then after 

 another three-quarters of a mile of drift 

 and forest- covered mountain-side, quartzite, 

 charged with pyrite, constitutes the country 

 rock. Anorthosites appear not far away 

 along the mountain, but still, despite the 

 fragmentary exposures, one must believe in 

 the presence of a very considerable and 

 not greatly disturbed series of sediments. 

 Along the strike of the first mentioned 

 quartzite in the valley abundant limestones 

 are found within a mile. 



Instances similar to the ones which have 

 been cited could be greatly multiplied, for 



we have now recorded over fifty separate 

 exposures of the limestones in the eastern 

 mountains, but the range of phenomena is 

 fairly well illustrated by the above. In 

 most cases they are isolated fragments, too 

 much broken up by eruptives to admit 

 of working out extended structure, but as 

 one passes into Warren county the larger 

 manifestations of the undoubted eruptives 

 decrease and encouraging opportunities are 

 afforded to trace out folds or other struc- 

 tural features. In one or two cases this 

 has been done by me, and the coming sum- 

 mer the matter will be carried further un- 

 der the auspices of the State Geologist, but 

 more detailed work is required than we 

 have been able to attempt in the first recon- 

 noissance. 



For the greater areas of limestone on the 

 northwest, Smyth has found evidence of a 

 series of compressed folds, which pitch to 

 the northeast, and which are overturned so 

 as to dip on both flanks to the northwest^ 

 but his statements are as yet somewhat 

 guarded.* 



The Significance of Graphite. — Graphite has 

 been tentatively referred to in many places 

 as one of the criteria for determining the 

 presence of sedimentary rocks, and for a 

 moment its value in this respect deserves 

 consideration. While I am well aware that 

 it often appears in pegmatitic dikes or veins, 

 and indeed that the old historic mines at 

 Chilson Hill, Ticonderoga are based upon 

 deposits of this character, yet it is true that 

 the graphite is almost never met except in 

 close connection with the limestones or 

 their characteristic associates, or in areas 

 where these form a prominent feature in the 

 local geology. The commonest occurrence 

 is immediately in the limestones and hardly 

 an exposure of them or of the bunches of 

 silicates in them has been discovered with- 

 out the presence of the shining black scales. 



* Report of the State Geologist of New York for 

 1893, I., 497. 



