[aaxoxG] DOCHET (ST. CROIX) ISLAND 138 
GEOLOGY AND NATURAL HISTORY. 
The history of any place is deeply influenced by the physical 
environment, and some knowledge of this is essential to a full under- 
standing of ihe course of historic events. We must note, therefore, 
the natural circumstances and productions of Dochet Island. 
Geology. Geologically, Dochet Island consists of a base and core 
of solid rock rising to over fifty feet above high tide level, resting 
upon which is a mass of clay sand and gravel (Fig. 5). The basal 
rock, which may be seen nearly everywhere about the island, is a red 


Fic. 5.—Ideal median section through Dochet Island, as seen from the 
east. The horizontal line is that of high tide; the soil is dotted and the rock 
shown by angles. At the left may be seen Wright’s Nubble, and next it the 
sand bluff, 
granite, like that forming the western bank of the river, and believed 
by geologists to be of Devonian age and intrusive origin.* 
A question of very great interest now arises, as to the origin, 
or mode of formation, of the isolated rocky mass which forms the 
basis of the island. Why does it exist here, rising abruptly from 
the bed of a great river with deep water all about it? At present, 
owing to insufficient geological study of the region, this question 
cannot be answered. with any certainty, but clues exist which will 
enable us to form at least a theory of some probability. The rock 
of which the island is composed seems plainly to be intrusive Devon- 

? The Geological Survey (of Canada) map of Charlotte County, the only 
one yet published which colours the island, makes it Silurian, which is an 
error. There appear to be two bands of granite on the island, one of lighter 
red colour and coarser texture forming the northern end and western side, 
and the other of darker red colour and much finer grain forming the eastern 
margin, together with the southern end and the ledges to the southward. An 
approximate contact line between them may be traced along the eastern shore. 
While the western coast of the river is composed of this same granite, the 
eastern shore is not, at least not opposite the island, suggesting that a fault 
line, or line of contact must run, doubtless following the deeper channel, along 
the river on the eastward of the island, a line which may be connected with 
the formation of this part of the river and its extension into Oak Bay. Little 
Dochet Island, on the other hand, is of very different formation, being a coarse 
conglomerate supposedly belonging to the Lower Carboniferous formation 
(newer than the Devonian), and it is probable that the line of contact between 
the two formations lies in the deep channel between the two islands. 
