On the Geology of the Llano! of Montreal. 20 1 



Riviere des Prairies is sandy in spots, and undulating ; but 

 on the whole, low. 



From the town of Montreal, eastward, the immediate bank 

 of the St. Lawrence is naked, and from twelve to thirty feet 

 high, with a gradual descent towards the end of the island. 

 In the opposite direction (toward Lachine) it is very low, the 

 land between the ridge just described and the river (a large 

 triangular space) being marshy, but still with small embank- 

 ments, indicative of water courses, which have once insulated 

 the southern angle of the island. This flat has been chosen 

 as the route of the canal between Montreal and Lachine, now 

 in operation, to within half a mile cf the former place. 



This topographic notice may suffice for the geological de- 

 tails now to follow. A tolerable idea of the population, agri- 

 culture, and scenery of the island, may be collected from the 

 writings of the meritorious Bouchette, and those of Lambert 

 and Hall. 



The environs of Montreal abound in geological facts of 

 great value. The lowest rock is a trap, of a kind unique in 

 the Canadas. By its peculiar composition, (which includes 

 all the ingredients of granite,) and by its associations, it illus- 

 trates in a beautiful manner the affinity existing between the 

 formation of which it is a member and the primitive class in 

 general. The mountain of Chambly, sixteen miles east by 

 south, affords the nearest of the older rocks in place. The 

 extended trappose ramifications which it has projected into 

 the superincumbent horizontal layers of limestone, without 

 injury or displacement accruing to them, are very remark- 

 able appearances, and to me inexplicable, except by supposing 

 parity of age, an opinion making this rock, junior to the other 

 inclined strata of the St. Lawrence, which are evidently of a 

 date long anterior to this limestone. An opportunity is here 

 furnished of examining the line of union of rocks extremely 

 dissimilar in their materials, and in their origin also, according 

 to prevailing theories. We shall find the limestone and it? 



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