[bailey] volcanic ROCKS OF NEW BRUNSWICK 131 



conspicuous colour-bands indicating stratification at low angles. Finally 

 they do not, as in the Huronian of St. John county, show any inter- 

 bedding of felsites with felspathic sandstones, fine grained diorites or 

 slaty dolomites. On the contrary the only rock with which the felsites 

 of the upper Nepisiguit have been observed in contact, and that in the 

 relation of being directly overlaid by the felsites as well as partly in- 

 terstratified with them, is a coarse conglomerate, the aspect and com- 

 position of which is identical with that of beds of such rock forming 

 a well marked member of the Silurian succession in Carleton county. New 

 Brunswick, and Aroostook county, Maine. It would therefore seem that 

 an the point at least where this observation was made by the writer only 

 two years ago, viz., on the slopes of Mount Teneriffe on the Nopisiguit, 

 the facts point much more strongly to the Silurian age of the volcanics 

 in question than they do their Pre-Cambrian origin. Of other parts 

 of the same region the evidence is not as yet so decisive, and probably 

 some of the felsites there met with are intrusive dykes, but, from such 

 observations as he has been able to make, the writer feels confident that 

 large areas until recently regarded as Pre-Cambrian arc really much 

 more recent and that a general revision of the geological structure of 

 the Northern Highlands will lead to very different views from those 

 which have previously prevailed. 



These conclusions, derived from personal observation in the field 

 and from comparison of macroscopic characters, apparently receive con- 

 firmation from their pétrographie or microscopic examination. Such 

 examination, based upon a series of slides made from the Nepi^iguit 

 and Tobique rocks as collected in 1902 by the writer and j\Ir. E. A. A. 

 Johnston, has been made by Mr. G, A. Young, of the Geological Survey, 

 with the result of showing that the series contains rocks quite unlike 

 those of the Pre-Cambrian system, and on the other hand quite remark- 

 able for their comparatively recent aspect. Speaking of them as a 

 Avhole, Mr. Young observes: 



" The thin sections submitted for microscopical examination are 

 all of volcanic rocks or their tuffs. The types of effusives represented 

 include granophyre, quartz-porphyr}'', devitrificd rhyolite, andésite, por- 

 phyrite and basalt, with tuiïs of quartz-porphyry and porphyrite. While 

 the rocks are always devitrificd and nsiially more or less decomposed 

 and altered, yet the structures typical of volcanic rocks and their glasses 

 are frequently retained, such as banding and flow-structures, spherulites, 

 ■perlitic cracks, lithophyses and drusy cavities." 



As examples of more minute structure and as typical of the region 

 in general, the descriptions of two slides may be added, the first from 



