176 NEW YORK STATE MUSEUM 



and the sands whicli overlie it as one formation. According to 

 him the chemical composition of the clays is as follows: 



Water of absorption 4.25 



Organic matter 1.17 



Sulfate of lime 1 



Silicates G9 . 02 



Peroxid of iron and alumina 17.24 



Potash .14 



Carbonate of lime 4 



Magnesia 3 



99.82 



A trace of chlorid of sodium exists. No exact statement of 

 the source of chlorid of sodium in this clay can he given. If it 

 were marine it would be expected that considerable traces of com- 

 mon salt and other sea salts would be found. The trace of 

 chlorid of sodium noted by Emmons has no bearing on the marine 

 origin of the clays since such traces are found in the surface 

 waters even of the Berkshire hills.^ 



Mr Asa Fitch M. D.^ employed the term " Albany clay form- 

 ation '^ in 1849. He stated : '' As neither its geological age or 

 name is well settled, I prefer designating it the Albany clay." 



Mr Fitch^ noted, the essential continuity of the clays from the 

 Hudson valley to Whitehall and thence into the Lake Champlain 

 valle3\ In most of Washington county the clay rests directly on the 

 Hudson river slate, though extensive beds of gravel locally inter- 

 vene. East of Comstock's landing the clay is stated to be 20 or 

 more feet thick. In a railroad cut across the river from Fort 

 Edward, Mr Fitch noted sand layers alternating with clay with 

 local unconformity between these beds and an overlying sand 

 deposit containing boulders of the underlying clay beds. 



Lake Albany doubtless began on the south in the waters stand- 

 ing in front of the retreating ice sheet prior to the opening of 



SS'cc Mass. Stiito lid of IToaltli, 23(1 Rop't, with ninp. Boston 1892. 

 ^Historical, Topoi^Taphical and Ai^ricnllural Snrvcy of the County of 

 Washinfe^ton. N. Y. State Agric. Soc. Trans. 1849. 1850. 9:872. 

 H. c. p.873-75. 



