of Bitumens, and of Bituminous Shales. 169 
made towards a knowledge of the chemical conditions necessary 
to its formation. : 
The natural vil springs, which occur in various parts of west- 
ern Canada, are upon the outcrop of the Corniferous limestone, 
or or the overlying Hamilton shales, and are along the line of a 
broad and low anticlinal, which rans nearly east and west through 
the district. In the towns ip of Dercham, where small quanti- 
ties of oil rise to the surface in several places, the Corniferous 
formation is overlaid by about forty feet of clay and sand, after 
sinking through which the limestone was bored to the depth of 
thirty-six feet. From this opening a few barrels of petroleum 
Were obtained. Oil springs abound for several miles along the 
hames, about sixty miles to the westward of Dereham, and 
borings into the limestone beneath have furnished considerable 
page 165, forms layers of considerable extent at the surface of the 
ground, and around the roots of growing forest trees. Two of 
these layers have together an area of more than two acres, and 
@ thickness which varies from a few inches to two feet. They 
are locally known as gum beds. In sinking a well in the vicin- 
ity of an oil spring in this region, there was found, beneath a 
depth of ten feet of clay, and reposing upon four feet of gravel, 
a layer of bituminous matter like that just described, from two 
to four inches in thickness. It is easily separable into thin lam- 
ine, which are so soft as to be flexible, and show upon their 
Surfaces the remains of leaves and of insects, which had become 
imbedded during the slow accumulation and solidification of the 
Manner in which beds of bituminous rock may sometimes be 
d 
than that obtained directly from the rock below, on boring which 
abundance, and often with great force, sometimes attaining the 
