184 ON THE ROCKS OF THE QUEBEC GROUP. 



in the discharge of their duties appears to me, on the present 

 occasion, to require a few words of reply, lest you and others might 

 suppose the accusation to have some foundation. It is due to Mr. 

 Marcou to give him credit for the very great care he claims, as I 

 am persuaded he would not have ventured so unreserved and con- 

 demnatory a contradiction of what has been stated on the part of 

 the Survey, without having exhausted all his skill on his own in- 

 vestigation. The only critical remark therefore left for me to 

 make, is that this distinguished stratigraphist has been very unfor- 

 tunate ; and that having missed the main feature of the conspicu- 

 ously marked structure he so carefully searched for, it is not 

 surprising that he should find a difficulty in understanding a 

 statement connected with it. 



In 1854 and 1856, a considerable time was expended by Mr.. 

 Richardson, one of my assistants, and myself, in ascertaining by 

 measurement the position and extent of all the exposures of the 

 limestone conglomerates which characterize Point LeVis. The 

 result of this work was exhibited by me to Mr. Marcou, at the 

 office of the Survey, in 1861, on an unpublished manuscript map, on 

 a scale of six inches to one mile, showing nearly all the known 

 exposures of rocks of the Quebec group for about twenty miles 

 below, twenty miles above, and nearly twenty miles to the south- 

 eastward of Quebec. This map represents an area of 800 square 

 miles, on which all the exposures are laid down by admeasure- 

 ments, comprising the work of one member of the Survey for two 

 seasons, and of another for one season. The measurements at 

 Point Le"vis I have recently re-protracted on the same scale,, 

 with a view of completely separating what is exposed to view, from 

 what is inferred ; and apian reduced from this to one half, by photo- 

 graphy, accompanies the present communication. The topogra- 

 phical as well as the geological features are delineated from the 

 measurements of the Survey. 



On this plan, the heavy black bands represent the known ex- 

 posures of the limestone conglomerates ; the dotted lines between 

 different exposures represent their supposed connection. Some of 

 the geographical undulations are shown by what I have desig- 

 nated the Coast Ridge, and the North, Middle and South Ridges. 

 The main feature of the Coast Ridge is a thick band of limestone 

 conglomerate extending in a hill and precipice, which overlook 

 the beach from Patton's wharf to the neighborhood of the Lower 

 Ferry; beyond which it gives place to the cliff immediately 

 behind the houses near the Lower, Middle and Upper Ferries. The 



