Correspondence. 355 
New York system divided iato Cliampluia Ontario, Helderberg, Erie 
and Catskill divisions. A. W. Vogdes. 
Fort Hamilton, N. Y. Sept., 1888. 
Geology op the vicinity of Quebec City'. — In the August number of 
the American Geologht, p. 134, Mr. A. R. C. Selwyn claims that he first in- 
timated in 1879 that, '"the so-called Quebec rocks of the town of Quebec 
are not of Quebec age at all" as professor Lapworth says, in his paper of 
1886, and he congratulates himself that professor Lapworth "fully con- 
firmed his views." On the contrary professor Lapworth instead of regard- 
ing the rocks of the town of Quebec as being the equivalent and a sort of 
special facies of the Utica Lorraine group, aljove the Trenton,as Mr. Selwyn 
thinks, referred them to a group helow the Trenton, without assigning them 
to any special position in the different groups existing between the Point 
Levis group and the Trenton, a difference of the first order between the 
two observers. 
Many years before Mr. Selwyn, I described, in 1862, "the great group of 
black slates of the city and citadel of Quebec"as a special formation, entire- 
Ij' distinct from the Point Levis group, and above it; and I have regarded 
that special group as contemporaneous with the Swanton slates of Vermont 
(See Letter to M. Joachim Barrande, on the Taconic rocks of Vermont and 
Canada, p. 12. and the Tabular view accompanying, Cambridge, 1862.) 
Mr. Selwyn adds: ''The stratigraphy which professor Lapworth has no 
knowledge of, has been carefully worked out by Logan and myself, and 
by other members of the Canadian survey, and I cannot learn that any one 
ever saw the shales beneath the Trenton limestone, as shown in Mr. 
]Marcou's section fig. 8." But Mr. Selwyn fails entirely to say what rocks 
the Trenton limestone lay over; his negation of my observations has no 
base to rest upon. On the edge of the plateau of Tresplat, at less than 
fifty feet from an out-crop of slates dipping S.S.E. at an angle of 45 
degrees, the Trenton limestone lies horizontal, and is only fifteen feet 
thick. I saw the slates at two quarries, on the plateau, in 1849 and in 1862. 
It will not be difficult for members of the Canadian survey to see the 
contact of the two groups of rocks, by direct diggings, if not otherwise. 
In regard to Dr. Emmons' "Geology of Montmorency,"1847,I have read 
that paper many years before Mr. Selwyn came to Canada, and I am glad 
to see it re-printed in full in The American Geologist, August, p. 94. Em- 
mons did not find a fault, but only says: "This association of rocks taken 
in connection with their position, indicates some derangement; and a close 
examination would undoubtedly result in the discovery of an extensive fault, 
or uplift, along the line which the road passes." Only a hint, passed over 
entirely by Logan fourteen years later. Dr. Emmons did not go to Charles- 
bourg, and consequently did not see my section with the Charlesbourg 
shales under the Trenton limestone. 
The "landslides" are evident on both sides of Montmorency falls. Big 
packs of Trenton limestone are seen now, resting on the asperity of the 
quartzite on which they hang,onthe right side of the fall. At my last visit, 
in August 1863, the water was very low, and I was able to approach and 
