REPORT OF THE DIRECTOR I914 143 



of differential movements within the Trenton formation due to 

 lateral pressure at the time of the thrust faulting. 



The submarine gliding hypothesis, as set forth by Hahn, may 

 well enough be the correct explanation of intraformational corru- 

 gations in certain regions but, as ^bove shown, there are insuperable 

 difficulties in the way of applying this hypothesis to such phenomena 

 at Trenton Falls. It would seem that Hahn has fallen mto a com- 

 mon error of making a single hypothesis or explanation altogether 

 too inclusive in its scope. 



THE GREAT RIFT ON CHIMNEY MOUNTAIN 



BY WILLIAM J. MILLER 



THE MOUNTAIN AND ITS LOCATION 

 Chimney mountain lies 7 miles south-southeast of Indian Lake 

 village in the ^Adirondack mountains and in the northwestern por- 

 tion of the Thirteenth Lake quadrangle of the United States Geolog- 

 ical Survey. While making his headquarters at Indian Lake during 

 the summer of 1914, the writer's attention was repeatedly called to 

 a rather remarkable feature toward the top of the mountain and 

 variously ascribed to " some convulsion of nature," " volcanic 

 action," or the *' splitting open of the mountain." This paper very 

 briefly gives the results of an examination of the locality, and it is 

 in fact not much more than an explanation of the accompanying 

 plates and figures. 



Chimney mountain has two summits about a fourth of a mile 

 apart, the eastern point reaching an altitude of 2705 feet, and the 

 western point about 2640 feet. The Hamilton- Warren county Hne 

 passes across the mountain between these two summits. Facing the 

 west, the mountain side is very steep with a descent of 900 feet in 

 a half mile. 



THE GREAT RIFT 

 The phenomenon of special interest is a great rift with strike 

 N 20° E directly across the eastern .summit of the mountain (see 

 plate I and figure 3). Exact figures were not determined, but the 

 rift has an estimated length of 600 to 700 feet ; maximum depth of 

 200 to 250 feet ; and maximum width across the top of 250 to 300 

 feet. On the eastern side of the chasm, the wall is very steep to 

 almost precipitous, while the greatest angle of the slope on the 

 western side is about 50 degrees. The highest point is the summit 

 of the so-called " Chimney rock " which rises pinnaclelike on the 

 eastern side of the chasm (see plate 2) and some 50 or 60 feet higher 

 than the highest portion of the western side of the chasm directly 



