Geology of Canada. 7 
trough of slates and sandstones, more or less calcareous, which is 
prolonged into Vermont. In Yamaska mountain a mass of trap 
lies in the line of the St. Hyacinthe sandstones and red slates 
and brings up on its flanks similar sandstenes and bluish and 
greenish slates, with a crystalline yellow-weathering limestone. 
The sandstones near the tra rap contain mica and plumbago. 
These rocks, however, are not seen upon the line of section, 
but in their strike occur the bluish and grayish calcareous and 
arenaceous shales, which are followed by light greenish and ash- 
gray slates, interstratified with gray sandstones. Following these 
appear the réd slates with green bands and their accompanying 
sandstones, which are sometimes finely conglomerate and more 
or less calcareous, often containing mica and graphite. These 
are associated with bands of a greenish chloritic Simian, hold- 
ing small portions of oxyd of chromium in some form, and near 
the base, with one or two beds of greyish limestones. South of 
this section line, the strata on each side of this deposit converge, 
but northwardly the breadth gradually increases, and seems to 
show that these rocks form a trough more or less disturbed by 
undulations. Following the western side of the trough, the slates 
with their accompanying sandstones, crossing the St. Francis, are 
seen at St. Nicholas on the St. Lawrence, and in the rear of Point 
Levi near Quebec. On the eastern side, the slates are followed 
to Roxton, where affected by an ee they sweep r 
towards Shefford Mountain, and thence are traced to Inverness 
on the Becancour, accompanied by hi He gir limestone, already 
mentioned as associated with them at the base. Beyond these, 
on the line of section, are a set of gray and black clay slates, with 
thin-bedded sandstones and limestones, which although present- 
those 
efford, w 
described as carrying” the sandstones to the east; thence upon 
another anticlinal across the Nicolet, where the dark slates and 
around into a narrow anticlinal valley which 
vith the other anticlinals, and is continued to the 
) the township of Sut 
a contains two great masses of trap, which 
e and Shefford mountains, and appear to have 
disturbed and ijered the rocks to a considerable extent. South 
of these. intrusive rocks we have first upon the section, greenish 
aoa eke clay slates, followed by a belt of silicious and calcareous 
which vary from a somewhat arenaceous limestone to a 
feebly calcareous sandstone. ‘These are seen in some places divi- 
three bands by the intervention of clay state, probably 
lations, which produce repetitions. 
