'236 Scientific Intelligence. 



the west, part are under the waters of Lake Champlain. The 

 rocks may be best studied along the shores and on the islands of 

 the lake. 



The terra Calciferous is used in its original signification, and 

 includes all the rocks lying between the Potsdam lying below, 

 and the Chazy above. The boundary lines are at present provi- 

 sional. The lower is just above the fossiliferous Potsdam, the 

 upper just below a sandstone which is assumed to be the base of 

 the Chazy, one recognized by the Canada survey, and which may 

 possibly correspond to the St. Peters Sandstone of the west. 



The Calciferous formation is essentially one of magnesian 

 limestone; it contains, however, pure sandstone, pure limestone, 

 together with mixtures of these, a calciferous sandstone, whence the 

 name. 



The rocks have a greater thickness than previously attributed 

 to them, and contain many fossil forms. Subdivisions are made, 

 based upon lithological and faunal characteristics. These are 

 named A, B, C, D and E, and are read from below upwards. 



Division A rests upon the uppermost member of the Potsdam. 

 The rock is a dark bluish gray magnesian limestone, mostly mas- 

 sive, more or less siliceous, weathering dark or sometimes with a 

 tinge of yellow. White quartz nodules appear in some of the 

 higher layers, and near the top, large masses of black chert. 

 Thus far no distinguishable fossils have been obtained. It has 

 a thickness of 310 feet. 



Division B is marked by the presence of nearly pure reticulated 

 limestone, weathering white, intermingled with light colored 

 dolomite. The bedding is obscure. The pure limestone which 

 occurs near the middle and again at the upper part is like the 

 Birdseye limestone in flinty compactness and fracture. Well- 

 marked fossils are found in B. Thickness, 295 feet. 



Division C is sharply separated from B below by a peculiar 

 fine-grained sandstone containing calcareous matter, and which 

 on weathering resembles fine-grained wood. Some of these lay- 

 ers are pierced with worm burrows. Thickness, 350 feet. 



Division D is made up of many varying rocks. Blue lime- 

 stones form the base. Above are magnesian limestones, and 

 sandy limestones, the latter weathering to a rusty rotten stone. 

 Still above are dark magnesian limestone and tough sandstone, 

 sandy limestone weathering into bands, blue limestones with 

 very tough slaty layers which give it a peculiar and character- 

 istic appearance on the exposed edges, pure limestone and some- 

 times conglomerates. Very fossiliferous. Thickness, 375 feet. 



Division E has fine-grained magnesian limestones weathering 

 various tints. Occasionally pure limestone layers occur, -and 

 rarely thin layers of slate. The limestones and slates are fossilif- 

 erous. Thickness, 470 feet. 



For all the five divisions of the formation there is a thickness 

 of 1800 feet. 



Sections of the rocks in different localities show great uni- 

 formity in characteristics of thickness and lithological structure. 



