DISi USSION. 



Mr. ( '. I> Walcott : The authors have stated in their paper thai the 

 Calciferous terrane lias a thickness of 1,800 feel in the Shorehara section, 

 between the Potsdam sandstone and theChazy limestone, and thai there are, 

 probably, Too feel of the < 'hazy limestone in the valley of Lake ( !ham plain. 

 Heretofore 300 or I"" feet of strata have been assigned to the Calciferous, 

 and not much more to the Chazy. One of the breaks in our knowledge of 

 the lower Pah >zoic rocks of the Champlain valley has been that which is 

 now covered so thoroughly by these sections. 



Reference is made in the paper to the section at Pillipsburgh, Canada, 

 given by Logan in 1863. This section lias a thickness of 1,890 feet. The 

 base and summit of the section were not defined, as Logan * 1 1 < 1 not observe 

 cither contact. During the j>a-t summer I found, mi Lake Champlain, a 

 small outcrop of Potsdam sandstone, with characteristic fossils, subjacent to 

 the limestone of the Calciferous terrane. I measured the section through to 

 the summit of the Chazy /.one. ami it gave a thickness of 1,750 feet, with one 

 hiatus caused by a fault in the Calciferous portion. The Calciferous fauna 

 ranges through the lower portion of the section and passes into the Chazy 

 fauna about 1,400 feel from its base. It is impossible to draw any line of 

 division between the Chazy and Calciferous in the Pillipsburgh section by 

 stratigraphic or paleontologic evidence. 



The authors state thai this series of rocks has been traced south to the 

 \ ■ w Jersey line and north to Phillipsburgh, Canada. During the past field 



son I examined the Phillipsburgh section and then went to Quebec, on 

 the St. Lawrence, where the limestones have nearly all disappeared and the 

 -hales form most of the section. There i- a hand of limestone near the base 

 that carries the same fauna thai I found in the middle portion of the Cal- 

 ciferous part of the Phillipsburgh section. As the Point L6vis graptoli 

 occiii- in the .-hales immediately associated with the limestone, thi- identifies 

 the graptolitic fauna as of middle Calciferous age. In the bed of lim< 

 at Point Levis there are numerous fossils in the lighter colored lim< stones in 

 which I found fossils of the upper Cambrian or Potsdam age. Tracing the 

 Calciferous from New Jersey across Pennsylvania and Virginia into Ten- 

 le — ••> . we find the same series of rocks, which are there known as the Knox 



dolomite. I crossed the section in Te «see a few weeks after studying the 



Phillipsburgh Bection and recognized the upper Chazy zone, and then the 

 change of fauna thai passes into the Calciferous. At the base of the Knox 

 dolomite the upper Cambrian or Potsdam fauna is found in the Knox -hale 

 just a- it i- found, in the Phillipsburgh section, in the Potsdam sandstone at 

 the base of the Calciferous. The- Knox dolomite, I believe, is given a thick* 



