June] NATURAL HISTORY SOCIETY. 221 



to the trappean hills, including the one upon which the party 

 was standing, which occur in tlie area between the two great 

 mountain ranges just described. It had been stated that Beloeil 

 was a granitic mountain and belonged to the Appalachian chain ; 

 but this was a mistake. In the first place, these rocks are not 

 granitic ; in the second place, they do not belong to the 

 Appalachians, to which they had been referred; and thirdly, 

 they differ from the Appalachian hills, which are all stratified 

 rocks. These mountains around us are all volcanic in their origin 

 and are composed of unstratified rocks. There are marks of 

 a great rupture of the earth at intervals, which might be traced 

 in the valley. Along this fissure or line poured, in olden times, 

 a great quantity of volcanic rock. This valley of the St. Law- 

 rence was then in a state of great volcanic activity ; and there 

 were burning mountains, earthquakes, and disturbances such as 

 now occur on the Pacific coast and along the Mediterranean ; and 

 some mountains poured out masses of lava. These hills are the 

 bases or roots of so many volcanic cones. These cones 

 were probably much higher than the present mountains, and 

 their roots were altogether buried in the soft rock which then 

 filled the whole valley to a level above some of these mountains. 



At a very early period, much of this filling was removed by 

 water, and subsequently, in the Post-pliocene period, the great 

 polar current swept down this valley, carrying with it icebergs, 

 and grinding and wearing away all the soft parts, until finally 

 this harder mass resisting its action, remained in bold relief. 

 This rock is of a harder, denser texture and is less liable to wear 

 down than Montarville and most of the other mountains, and, for 

 this reason, it is higher. These rocks have a distinct character : 

 Rigaud and Montreal differs from this ; -Boucherville differs very 

 widely from it, and Yamaska differs somewhat from either. Brome 

 and Shefi'ord are unlike anything else you find in these. You have in 

 these mountain peaks some of the most remarkable and varied types 

 of eruptive rocks. The erosion just mentioned will account for 

 the very singular and level aspect of the scenery around these hills. 

 It is extremely difficult to fix the precise age of these rocks, even 

 geologically. But these mountains were old when the first sands 

 of the Alps and the Himalayas were at the bottom of the deep. 

 There was another curious story : from the evidence of the 

 existence of Devonian limestone on the other side of the lake, it 

 appeared that after the earlier erosion there was again a filling 



