ISO ROYAL SOCIETY OF CANADA 



bright red weathering, constantly attract attention. It has been usual 

 until recently to regard all these rocks as Pre-Cambrian, and they are 

 so represented in the maps of the Geological Survey. But the reference 

 was wholly based upon lithological grounds and those only of macro- 

 scopic characters, no superposition of undoubted Cambrian strata being 

 here met with to show their anterior origin, and no petrographical 

 examination of their nature being made. It is well therefore to look 

 closely into these lithological features and resemblances, more especially 

 as certain stratigraphical facts, recently observed, go far to suggest a 

 much more recent origin for the beds in question. 



In the first place then it may be observed that the term "felsites ' 

 very inadequately expresses the nature and variety of rocks to which it 

 has been applied. On the contrary while, to the eye alone, some of the 

 rocks in question are evidently mainly composed of felspar, and are 

 granular crystalline and homogeneous through large masses, the pre- 

 vailing rock is a rhyolite rather than a felsite, often porphyritic and in 

 places amygdaloidal, while at times it presents the character of a breccia. 

 While the more crystalline portions are sometimes and possibly are always 

 of the nature of dykes, the more earthy varieties, including rhyolites 

 and ash-rocks, alternate with ordinary sedimentaries, and at times show 

 conspicuous bandings which would appear to be the result of aqueous 

 deposition rather than of igneous flow or merely mechanical movements. 

 In all these respects they bear a much closer resemblance, in the opinion 

 of the writer, to the volcanic portion of the Upper Silurian, as found 

 elsewhere in New Brunswick and Maine, than they do to the effusive 

 rocks of the Pre-Cambrian systems already described. Indeed, placing 

 representative series side by side, one not only notices the almost exact 

 repetition in the Nepisiguit series of the Silurian " volcanics " as de- 

 veloped around Passamaquoddy Bay, even down to varietal differences, 

 but is almost equally struck by the absence, both in the Nepisiguit and 

 the Passamaquoddy areas, of some of the most conspicuous members 

 of the typical Huronian rocks as developed about St, John. Thus 

 nearly the whole of the Huronian rocks are remarkable for their highly, 

 silicious character, as indicated by the name of petrosilex under which 

 they were originally described, and they are still often glassy in fracture 

 and contents, wihile in the rocks of the Nepisiguit they are almost always 

 dcvitrificd. 



Nor do the felsites of the northern counties exhibit anything like 

 that variety of colours — pale pink, green, purple and salmon red or 

 ribbanded — which are so noticeable in the south. Dark gray and red- 

 dish gray, weathering a bright brick red, is their prevailing hue, just 

 as in the case of Chamcook hills and McMaster's Island, Like the 

 latter they arc porphyritic or amygdaloidal and in places marked by 



