152 NEW YORK STATE MUSEUM 



beds of the formation. Very interesting exposures of this same 

 rock are to be seen along the Saranac river for some 2 miles above 

 and below Cadyville. Here the thickness has been estimated to be 

 over 1000 feet. The downwarping of the basin of the old Potsdam 

 sea continued and its shore lines near Plattsburg retreated south- 

 westerl}^ In off-shore waters new beds containing much lime 

 were deposited on the top of the former sand beds. These 

 newer rocks are easily recognized by their lithologic and other 

 characters and have been named the Beekmantown formation 

 because of their interesting exposures in Beekmantown township. 

 Professors Brainerd and Seeley of Middlebury College gave much 

 study to this formation in the Champlain valley and estimated its 

 thickness to be in the neighborhood of 1800 feet. Beds of this 

 age are well exposed along the lake shore for about a mile and a 

 half south of Valcour bay. At the end of Beekmantown time 

 there seems to have been a local cessation of deposit. On its 

 recommencement the deposits were of a markedly changed char- 

 acter and were laid down on a much modified surface of the Beek- 

 mantown formation. The new deposits were named for the town 

 in which they were well exposed and first thoroughly studied,, 

 constituting the Chazy formation. These are the rocks that form 

 the great Bluff Point mass. Their thickness, as measured on 

 Valcour island, is close to 988 feet. Over the Chazy beds there 

 were deposited in succession those of Lowville and Black River 

 age and over the latter the rock beds known as Trenton. 



It will be proper here to ask how we may distinguish rocks of 

 Trenton age from those of Chazy age. and as the outcrops at Cliff 

 Haven show very many of the interesting differences in these 

 deposits, we will call attention to a few of them. 



Many of the ancient builders of Babylonia inscribed their bricks 

 or molded them in inscribed forms. Because they did so we may 

 now determine the date of the laying of many ancient pavements 

 and corner stones. So too the maker of the Trenton pavement 

 stamped it with his own easily recognized seals, which are far 

 more numerous and more wonderful in character than an}^ inscrip- 

 tions left by either Sargon or Nebuchadnezzar. Trenton seals in 

 the form of exquisite brachiopod shells, bryozoa and other remains 

 of denizens of an ancient inland sea, may be found in the first rock 

 ledge outcropping on the lake shore just south of the Cliff Haven 

 steamboat landing. The southernmost Trenton exposures are more 

 barren of life forms but even here the writer has found the beauti- 

 ful stems of " stone lilies " and the delicate frondlike forms of 



