128 ROYAL SOCIETY OF CANADA 



blende-basall, felspathic diabase, augite-porphyrite and (though very 

 doubtfully) a basic glass or Tachylite. 



In western central New Brunswick a very interesting band of vol- 

 canic rocks is to be found in the western part of Carleton county, where 

 it constitutes a well marked belt about twenty-five miles in length and 

 t\vo to three in breadth, stretching from the vicinity of "Woodstock to 

 Monument settlement near the boundary of Maine. Near Eel Kiver it 

 includes the somewhat prominent ridge known as Oak Mountain, and 

 it is in this eminence and along the upper courses of Eel Eiver that its 

 most ehara.cteristic features are to be seen. 



In their general aspect these rocks frequently suggest comparison 

 with the "volcanics" of the Huronian, the occurrence of amygdaloidal 

 ash rocks and of breccias, the latter only recognizable as such through 

 the effects of weathering, being especially noticeable, but differ in being 

 usually more distinctly basic, with fewer felsites or porphyrites and 

 much iron and manganese. At some points the beds are markedly 

 spherulitic. The associated slates are sometimes intensely red, and at 

 ethers show a mottling of pale gray, red and purple colours such as are 

 often found associated with the products of igneous action. They are 

 here referred to in connection with the Cambrian system for the reason 

 that they are closely associated with a series of black slates carrying 

 remains of Didyonema sociale, usually supposed, to mark a Cam- 

 brian horizon, but the fact that they also closely adjoin strata carrying 

 Silurian fossils, leaves the question of their true age still undetermined. 

 Indeed, as will presently appear, the distinction of Huronian, Cambrian 

 and Silurian volcanics has always been a source of much doubt and 

 difficulty in working out the geology of New Brunswick. 



Silurian. . 



Next to the Huronian no system in New Brunswick shows so marked 

 an admixture of volcanic products, or so general a distribution of the 

 latter, as the Silurian. They are to be found in all parts of the province, 

 and in most instances form a conspicuous feature in the topography of 

 the districts in which they occur. 



Beginning in the southern counties the areas bardering and in- 

 cluding Passamaquoddy Bay ajTB especially noticeable for the evidences 

 which they afford of Silurian vulcanism. For though ordinary aqueous 

 sediments are abundantly displayed and abound in the characteristic 

 fossils of the era, they are almost everywhere surmounted by rocks of 

 igneous origin marking this region as one of pronounced volcanic activity 

 in the Silurian era. Among the eminences thus constituted may be 

 included the well known Chamcook Hills near St. Andrews, Troak's 



