30 BULLKTIX Of THE NATURAL HISTORY SOCIETY. 



of felsite of interniediatG age. ItB original nature is 

 ratlior doubtful, but it has been considered to be most 

 probably a consolidated volcanic ash. The series to 

 which it belongs is greatly developed to the north-east, 

 in the Quaco hills, and there is made up of ancient lavas, 

 volcanic breccias and ashes. The lavas are usually more 

 or less porphyritic, and some show, when sectioned, 

 indications of having once been partly made up of glassy 

 matter. 



It seems that in pre-Cambrian times southern New 

 Brunswick was part of a great volcanic region, which 

 extended down to the south-west at least as far as the 

 Carolinas. From the St. John volcanoes were thrown 

 out great quantities of lava and ashes, some on land, 

 some under water. The centres of eruption appear to 

 have been some miles to the east of the city, so that only 

 the finer ashes reached this far west, and formed the fine 

 felsite band. 



The parts of the lava flows next the surface would 

 cool suddenly and be glassy. Those farther from the 

 surface would be fine-grained, with usually some porphy- 

 ritic crystals, which had formed in the depths of the 

 earth from which the molten rock had come. Along 

 with the solid lavas vast quantities of pumice, broken 

 fragments of rock and fine ashes were cast up, the finer 

 ash drifting some distance with the wind. 



In the course of time these volcanoes became extinct, 

 were partly worn away, partly covered up by the sinking 

 of the land, and later sediments deposited on them. The 

 ashes and breccias were consolidated into a hard rock, 

 metamorphosed so as to be almost unrecognizable ; the 

 harder lavas suff'ered less change, but their glass was 

 converted into a felsitic mass, made up of exceedingly 

 minute crystalline grains of diiFerent minerals. Then, 



