3^ NEW YORK STATE ^LUSEUM 



south pendiilnm swung off the paper and failed to i agister for a 

 period of one second. The larger amplitude of the waves recorded 

 by that pendulum may have been due to more sensitive adjustment. 



September 14. A moderately strong movement recorded prin- 

 cipally on the north-south pendulum. Origin is not known. 



September 28. Slight disturbance, consisting of small waves 

 separated by intervals of quiescence. Main component regis- 

 tered by the north-south pendulum. 



LIMESTONE CAVERNS OF EASTERN NEW YORK 



In my report of last year attention was directed to the desirability 

 of acquiring more exact evidence of the character and origin of 

 the caverns which honeycomb the limestone region of the Helder- 

 berg plateau. There are many of these subterranean ways. They 

 have long been known to the residents of the region and have been 

 a source of popular interest partly because of the mysterious ob- 

 scurity in which they have been veiled. Their geological import- 

 ance lies chiefly in the relation of such underground passages to the 

 topography and drainage of the country, for this class of caverns 

 is: elongated channels produced either by solution of the limestones 

 or by subterranean erosion. The Helderberg plateau has been well 

 adapted to their development because of its peculiar though simple 

 g-eological structure. The region is one of continued succession 

 of limestone beds varying in degree of purity and the strata in 

 general are almost horizontal, whatever dip they have being to 

 the south. 



In the consolidation of these strata and by the strains they have 

 undergone in their uplift they have been deeply cracked or parted 

 without displacement of adjoining masses, by an intricate series of 

 vertical joints which has made the floor of the region a mosaic of 

 great limestone blocks. When solution or erosion has begun on this 

 area, it naturally selects these lines of least resistance and the ulti- 

 mate outcome is the production of cavernous channels in the rocks. 

 It is thus entirely clear that essentially the whole system of under- 

 ground channels stands in direct relation to and constitutes a part 

 of the drainage system. 



With the purpose of ascertaining these relations a party was 

 organized during the past season, instructed tO' explore and survey 

 all accessible caverns in this limestone plateau and to take note of 

 their relations to geological structure, drainage, topography and 

 The work was prosecuted with vigor though it 



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