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[Marcou. 
river Etchemin and La Chaudiere’s fall shows such outcrops of 
diabase protruding from the red, green, brown and black slates. 
Near the Chaudi^re’s fall these diabases are extremely phonolitic, 
ringing under the hammer like bells. Those dyke-beds ( filons - 
couches as they are called in French) intercalated into the grau- 
wakes or Taconic slates, recall the same phenomenon of dykes 
and intercalated beds of diabase ( porphyrites and Kersanton) 
which exist between the “Rade de Brest” and the “Douarnenez” 
bay in Britany (France). It seems that the eruption of those 
phonolitic diabases — a very remarkable example of ancient volca- 
nos during the Taconic period — prevented the existence of 
marine animals in the area directly under their actions, for no 
fossils have been found there yet. Near to it, however, at the 
crossing of the Railroad above Chaudi&re’s fall, a small brachio- 
poda, called Oholella preciosa , has been found. The same fossil 
has been collected by the members of the geological survey of 
Canada on the shores of the St. Lawrence river east of Arlaka 
junction, near the Hotel Victoria at Levis and at Pointe-a-Pizeau. 
The slates containing the Oholella preciosa, with some graptolites , 
lay directly below the Pointe-Levis group and are placed a little 
above the Elliptocephalus ( olenellus ) Tliompsoni beds found by 
the geological survey of Canada near Beaumont. The horizon 
of the Oholella preciosa can be taken as the approximate extreme 
limit between the Upper and Middle Taconic ; and the groups 
of the “Georgia slates” containing the Elliptocephalus Tliompsoni 
extend from Bic-Harbor to above Beaumont, east of Pointe-Levis. 
It is composed of the belt of slates, which rfms south of the local 
fold of Pointe-Levis, reaching the St. Lawrence again at the 
western extremity of the fold near the Old Victoria hotel ; cross 
the St. Lawrence to near the Pointe-a-Pizeau, following for a 
very short distance up the shore toward Cape Rouge. The dia- 
basic slates of the area between the mouth of Etchemin and 
Chaudiere rivers and Chaudi&re’s fall belong to that division of the 
Middle Taconic or Georgia groups. 
I was unable to find a single fossil in the red slates spotted 
with green and the gray reddish sandstone with ripple-marks, 
which form the masses of strata of the Chaudiere’s fall. At my 
first visit there in 1849, I was much struck by the exact similarity 
of the rocks with those existing at the fall of the river Montreal 
near the south-west shore of Lake Superior ; and I have no doubt 
