OF ARTS AND SCIENCES. 209 



The experience of 1861 had convinced me of the need of very 

 close and careful study on several chosen points in order to reach 

 any precise results as to the strata existing between the " schists 

 of Georgia " and the '" Utica slate." Tlie exploration of this year 

 was therefore devoted to Swanton, Pliillipsburgh, and Chazy on 

 Lake Champlain, and to Point Levis near Quebec. First, each 

 bed at Point Levis was studied with care, at the east of the vil- 

 lage and near the railway station ; and in the month of July I was 

 convinced that what had been considered as beds of limestone and 

 conglomerate were only lentils enclosed in the schist. This dis- 

 covery explained several outcroppings of magnesian limestone which 

 had embarrassed me the preceding year at St. Albans Bay, at Swan- 

 ton, and at Hiijhfiate. 



Dr. Emmons and Colonel Jewett had considered similar formations 

 in the neighborhood of Troy, New York, used for making lime, and also 

 those along the line of the Upper Tacoiiic from Canada to the Hudson 

 River, as hajs of Silurian limestone (Trenton or other) which were 

 deposited in Jioles or cracks of the black Taconic slate. They had 

 seen that, at several of these quarries, the lime was exhausted, there 

 being no more limestone. For them these bags of limestone were the 

 remains of the Lower Silurian which had extended thus far at the 

 time of the deposit, but which subsequent denudations had carried off, 

 leaving these bags of limestone to witness to their former extent. Some 

 rare and badly preserved fossils were found in these bags of limestone, 

 identical with, or at least very similar to. six or eight Silurian species 

 from the groups of Chazy and Trenton. 



The proof once reached, that the limestone lentils of Point Levis 

 were of the same age with the schists which enclosed and shut them in 

 too surely to admit the doubt of a later deposit, T went directly to 

 Swanton, seeking to verify the same fact in the limestones of this 

 eastern shore of Lake Champlain. I draft'-d exactly the surflice 

 appearances, and studied in detail several lime quarries, quite common 

 in this region. I found everywhere that the limestones were hn'iciilir 

 masses, some very limited in size, like boulders ; and others, on the 

 contrary, having the characteristic form of lentil^: and all so well en- 

 closed in the schists that they were penetrated by them, or they were 

 thrust into them like wedires. 



Further, T found these limestone lentils scattered at all levels of tlio 

 Upper Taconic, from its base in the schists at the east of the town of 

 St. Albans, to the boi-ders of Lake Champlain in the schists of Swan- 

 ton ; they were singularly placed, sometimes isolated, sometimes in large 



VOL. XX. (S. 9. XII.) 14 



