[bailey] volcanic ROCKS OF NEW BRUNSWICK 129 



Mountain and ]\Iount Blair near St. George, portions of the Mascareen 

 peninsula, MoMaster's Island and, on the \west side of the Ba,y, much of 

 Moose Island on which rests the town of Eastport. 



The rocks composing the hills referred to present the usual variety 

 of volcanic éjecta, including diorites and gabbros, more or less amyg- 

 daloidal; but the most widely spread as well as the most conspicuous 

 of these products is what has usually been termed felsite or porphyrite, 

 but is in reality rhyolite, a rock usually of veiy fine grain, sub-trans- 

 lucent and varying from dark gray to chocolate in colour, often weather- 

 ing to bright red, and having scattered through its mass numerous 

 minute crystals of orthoclase. It is much jointed, the joints being 

 often coated with crystalline epidote, and usually breaks with a broad 

 conchoidal fracture, without much evidence of sedimentation; but in 

 places stratification is clearly indicated by very regular colour bands, the 

 corrugation of which by pressure has given to the rock, when polished, 

 a resemblance to polished mahogany. Though for the most part resting 

 upon the fossiliferous portion of the Silurian succession, the rhyolites 

 are not only conformable to the latter but to some extent are inter- 

 bedded, thus proving their Silurian origin. Were it not for these rela- 

 tions some of these highly felspathic rocks might well be mistaken for 

 those of the Huronian system, and in visiting the region in 1873 in 

 company with Dr. T. S. Hunt the latter could not be persuaded that 

 they belonged to a more recent horizon until, their actual superposition 

 in nearly horizontal attitude was clearly shown. 



The difficulty of readily distinguishing between the volcanic and 

 semi-volcanic rocks of the Huronian and Silurian systems is again met 

 where these two great systems come together in the valley of the St. 

 John river in King^s county, and in the Kingston peninsula, forming 

 the southern side of Long Eeach, a lake-like expansion of this river. 

 It was not until the discovery of characteristic shells in what would 

 seem at first to be mere ash-beds that the latter were referred to their 

 true horizon. 



And now, with these comparisons in view, we may pass to the con- 

 sideration of another area the Silurian age of which has not until 

 recently been even suspected. T refer to that portion of the Northern 

 Highlands of the province in which are located the headwaters of the 

 Tobique, Nepisiguit and other rivers, a mountainous tract of which the 

 highest elevation, Mount Carleton, attains an elevation of 2,700 feet. 

 In traversing this region, as did the writer as long ago as 1863, one is 

 struck by the general prevalence of " felsites," so-called, especially on 

 the upper N'episiguit, blocks of such rock making up the greater part 

 of the bed of the stream, while about the summits of the hills and oc- 

 casionally at their base ledges of similar rock, made conspicuous by their 



