8 A. R. C. SELWYN ON THE 
black and dark-grey limestones, which are occasionally in sufficient quantity to be wrought 
for lime-burning. A mass of this description is quarried for the purpose on the twenty- 
sixth lot of the first range of Farnham, near the western limit of the area which has been 
described. The rock contains very small, almost microscopic trilobites and fragments of 
small brachiopods. The genera are: Ptilodictya, Graptolithus, Orthis, Leptena, Ampyx, Dal- 
manites, Lichas, Triarthrus, and Agnostus. The Ptilodictya strongly resembles P. acuta, and may 
be the same; while one, Leptæna, cannot be distinguished from Z. sericea. These fossils 
have a less ancient aspect than might have been expected in the Potsdam formation; so 
that the Farnham slates, with similar ones in other localities, may be brought into position 
by some of the many complicated dislocations which affect the strata. Except, however, 
where such fossiliferous strata are known to occur, the black slates and limestones will be 
provisionally described as older than the Quebec group.” 
“The anticlinal form which these slates are supposed to possess between the Province 
line and Ste. Croix can scarcely be proved from a comparison of the dips. These are in 
general at high angles, and though sometimes to the one side and sometimes to the other 
of the strike, they do not always coincide in direction with the results deducible from the 
geographical distribution of the strata, several of them being no doubt overturned dips. 
Such as are considered to be of this character generally point to the south-east, but this is 
not the case in every instance. The anticlinal form is rather to be inferred from the arrange- 
ment of the superior rocks on each side, and from the fact that the black slates and lime- 
stones are traceable nearly round the extremity of a trough of those rocks, through a trans- 
verse gap on the west branch of the Nicolet, into along narrow valley, which they occupy 
for the distance of about fifty miles along an anticlinal, which runs from Danville to Sutton, 
in a direction nearly parallel with the one already described.” Again, describing Sutton 
mountain, Sir W. Logan says, p. 247: “This mountain stands on an area which, near the 
Province line, has a breadth of about ten miles ; it appears to be composed of coarse chloritie 
and micaceous slates. In many parts the slates become very quartzose ; and they frequently 
contain a portion of felspar, giving to them the characters of gneiss; while in some parts 
they lose their schistose structure and break into large solid blocks.” And on page 251 he 
writes: “Sutton mountain, standing between these two anticlinals, with a height said to 
be about 4,000 feet, and gradually dying down before reaching the St. Francis, might be 
expected to present a synclinal structure. In three transverse sections, however, the strata 
have been observed to maintain dips, generally at high angles, in opposite directions from 
the axis of the mountain, with much constaney, for upwards of twenty-five miles.” 
In the foregoing extracts Sir William’s doubts are plainly expressed, and it seems 
strange that, with the conclusive evidence which he gives, together with his reasoning 
respecting the Farnham slates and limestones, he should have failed to see its application 
to the similar dark slates and limestones of Danville, Richmond, &e., but should have 
adhered to the idea that these latter were identical with the glossy black hydro-mica slates 
that are associated with the magnesian belts on either flank of Sutton mountain, and which 
extend thence north-eastward and constitute the great Quebec anticlinal, shown on the 
map now exhibited, and called (page 256, Geology of Canada) the Sutton and St. Joseph 
and also Sutton and Danville anticlinal. | 
I can, from personal examination, entirely confirm the description quoted of the three 
