192 Canadian Record of Science. 



Passing the Montreal "West Station, we reach the point 

 where the Valley conies into view, and here we observe 

 that while the Easterly side is lower than the West, the 

 slope of the surface towards the St. Lawrence is clearly 

 produced on the Eastern side of the Vallev as shown in 

 Fig. 2. 



From this we conclude that the bank, as laid down, 

 ■extended to and beyond the present line of the St. Law- 

 rence, and that the Valley was excavated by a stream of 

 water which formed a channel or branch of the St. Law- 

 rence, until, as the land continued to rise, the hard rock 

 near Lachine remained firm while a break or fissure at 

 the present Lachine rapids caused a lowering of the Water 

 which allowed it to drain off., below the level of the 

 Valley. 



From Lachine to St. Anns, there are places where the 

 limestone comes to the surface, and others where it is 

 covered by the usual glacial drift. At Pointe Claire 

 there is a mass of limestone, evidently in place from the 

 markings of the stratification visible from the Eailway, 

 which rises abruptly from the plain to the height, 

 apparently of about forty (40) feet, and through which a 

 wide level road passes where the stone has been removed 

 by quarrying operations. 



This was doubtless left in place when the surrounding 

 beds of limestone were removed by erosion, owing to the 

 part where the denuding forces struck it being harder 

 than the rest of the mass, possibly due to the presence of 

 a trap dyke or merely a harder bed of limestone. From 

 what remains some idea may be formed of the enormous 

 mass of limestone which has disappeared frOm the 

 surrounding country through the action of nature's forces. 

 Near St. Anns some rounded hills of sand and gravel 

 show where fierce currents, carrying with them the 

 materials which formed the sides and beds of the channel 

 through which they flowed, cast them into an eddy which 

 washed and heaped them up in its circular course. 



