14 Geology of Canada. 
oped in that of Lake Champlain, where it is recognized as the 
Potsdam sandstone. ‘To the northeast it probably skirts the base 
of the syenitic rocks, and has indeed been observed at the Falls 
of the St. Maurice, but owing . the great anil of tertiary deposit 
which fills the valley, the opportunities of examining it are but 
few. The next rock upon the line of section is a limestone, very 
silicious at the base, but pure and thick-bedded in the middle, 
gradually becoming bituminous and shaly toward the top. This 
formation, exposed at a very moderate dip, constitutes the greater 
portion of the island ot Montreal, and crossing below to the north 
side of the river, is lost beneath the tertiary sands and clays. 'To 
the south, it sweeps around the extremity of a trough, until it 
reaches St. John, where either turning over an anticlinal or affec- 
ted by a dislocation, . turns up the west side of the Richelieu 
and runs into New 
This formation is Fs by its fossils to be referable in its lower 
part to the calciferous sandstone, while the upper beds are the 
Trenton limestone. It contains interstratified greenstone trap, 
sometimes amygdaloidal, which constitutes the mountain of Mon- 
treal. Resting upon this limestone is a set of black shales which 
appear on both shores of the river before Montreal, and constitute 
some islands in its bed. ‘To the south, these shales, which are 
the Utica slates, follow the course of the limestone, keeping the 
east shore of the Richelieu, and spreading out to a consider- 
able breadth, constitute the region of country between the mouth 
of Lake Champlain and Missisquoi Bay. To these succeed a 
series of shales, bluish and grayish, arenacious, and more or less 
calcareous, which are evidently from their fossils the Loraine 
shales. These are seen upon the Richelieu at Chambly, upon 
the Yamaska near St. Hyacinthe, and in several other points 
along the line of strike. They present a considerable breadth, 
and are not improbably kept at the saris by some little undula- 
tions. Succeeding these, after tw 
tertiary sands, appears a saiatisins of the ' 
which have been traced from Philipsburg, upon the line of Ver- 
mont, through the Seigniory of St, Hyacinthe, to Deschaillons, 
where they cross the St. Lawrence, -_ are exposed again upon 
the northern shore. ‘These are follow ed by a repetition of the 
Utica slates and Loraine sles 3 which flank the limestones upon 
the St. Lawrence, and are exposed at various points along the 
strike. Upon the Barbue river, in the Seigniory of St. Hyacinthe, 
occurs what appears to be a small trough of higher rocks, consist- 
ing of heavy greenish sandstones, interstratified with red and 
chocolate-colored slates, sometimes mixed with green bands. 
These red slates are highly ferruginous, and sometimes —_ 
traces of oxyd of titanium. Near the line of Vermon 
succeeding the Trenton limestone, the extremity of a “similar | 
