94 L. W. BAILEY ON GEOLOGICAL CONTACTS AND ANCIENT 



brian, Mica-schist group aud Quebec group. Until within the last year or two, however, 

 no definite knowledge existed, either as to the true limits or relations of these several sets 

 of rocks, or even whether in the lower group there might not really be inchided several 

 distinct formations. In IS'TO, the base of the Upper Silurian in that part of Carleton County 

 lying east of the St. John River was approximately fixed by Mr. Matthew, and, simulta- 

 neously but independently, a like boundary was determined by myself between the town 

 of Woodstock and the Maine frontier. More recently both of these districts have been 

 reexamined and the line of contact of these formations carefully studied for a distance of 

 not less than thirty miles. Though somewhat obscured by overlying carboniferous sedi- 

 ments, the unconformity of the two is, nevertheless, strongly marked : first, in the occur- 

 rence at the base of the upper series of thick beds of calcareous conglomerate filled with 

 fragments (black silicious slate and petrosilex) derived from the group below ; secondly, 

 in a difference both of strike aud dip ; and thirdly, as a result of this diff"erence, in the pro- 

 gressive overlapping of the newer formation upon the several members of the older. The 

 fossils of the later group are numerous and varied, and indicate an horizon corresponding 

 either to that of the Niagara or Lower Helderberg ; in the lower are a few shells and 

 graptolites, together with fragments of trilobites, apparently of the genera Trinvdeus and 

 Harpes, biit too poorly preserved to be certainly determinable. 



The relations of these siipposed Cambro-Silurian rocks to the granite open up nume- 

 rous questions, as interesting as they are difficult. They present, indeed, only another phase 

 of the well-known Taconic controversy, so admirably summarized and discussed by our dis- 

 tinguished Vice-President in the lately issued volume of our Transactions. Into the broader 

 questions involved in this controversy it is not necessary, nor do I feel prepared, to enter ; 

 the objects of the present paper will be sufiiciently served by presenting a few facts of 

 actual observation in the field, with such conclusions as are of direct local application. In 

 the case of both of the great granite belts which traverse New Brunswick, the contacts of 

 the latter with the bordering stratified rocks are best seen along their northern edge, from 

 which overlying material has been for the most part removed, while it has been exten- 

 sively accumulated along that of the south. Where thus exposed it invariably presents 

 the following features : — 



1. The transition from massive, compact and uniform granite to the associated schists 

 or other rocks is instantaneous and abrupt. 



2. The invaded ])eds vary greatly in character, embracing coarse and fine gneisses, 

 mica schists, chloritic and hornblendic schists and fine micaceous sandstones. 



3. Foliation and crystallization are most marked in the vicinity of the granite, and 

 decrease in receding from the latter, but vary greatly in the apparent distance to which 

 the elfect has extended, this being in some instances only a few yards, while in others it is 

 several miles. 



4. The outline of the granite is irregular, and, while in part parallel to the strike of 

 the enclosing schists, at others it intersects these obliquely or even at right angles, or 

 sends into the latter irregixlar tongues. 



5. Detached masses or bosses, of various forms and sizes, border the main granitic 

 areas, indicating, beneath the schists, a wide-spread and uneven granitic floor. 



6. Granitic veins, not different from the main mass of the granite, but readily distin- 



