ABRAHAM GESNER REVIEW OF HIS SCIENTIFIC WORK. l!o- 



Tlbe Intrusive Rocks. 



Dr. Gesner at an early date recognized the granitic range 

 of the Nerepis hills as the key to the geological structure of 

 southern New Brunswick. He noticed also that the sediment- 

 ary beds resting on the ilanks of the granite hills were more or 

 less l)roken up, and to some extent Vjuried by extensive eruptions 

 of volcanic matter, and had been penetrated by numerous trap 

 dykes. This was the generalization he made at the end of his 

 first year's work. But in the second year of his survey, he 

 found that the true granite terminated at Belleisle Bay on the 

 river 8t. John; and he also discovered (or thought he did) that 

 the ridge of the crystalline rocks curved southward from there, 

 and as a belt of syenite, etc., extended westward along the 

 south side of the granite range, and eastward through Kingston, 

 the Loch Lomond hills and along the Shepody road to She- 

 pody mountain in Westmorland County. 



hi the foui'th year of his survey he traced another granitic 

 axis, extending from the Cheputnecticook Lakes, northeastward 

 toward Bathurst on the Gulf of St. Lawrence. The western 

 end of this axis is shown on the map, but the eastern lies beyond 

 its limit. 



In comparing this old map of Dr. Gesner's with that of Di'. 

 lloblj, who was his successor in the study of the geology of Ne-v\' 

 Brunswick, one may observe that in some respects the former is 

 more accurate than the latter, as, for instance, in the boundary 

 of the granitic area of the Nerepis hills ; and theoretically more 

 correct in other respects, as, for instance, in the distribution of 

 the syenite and trap rocks, which by Dr. Robb are represented 

 as round isolated masses in many cases, but by Dr. Gesner as 

 occupying elongated areas. Among the metamorphic tracts 

 these intrusive rocks have usually come out through long fissures 

 parallel to the general trend of the several bands of sedimentary 

 rock. Only within the Carboniferous area, and at Grand Manan,, 

 are there broad sheets of eruptives undisturbed. 



liater studies on the " trap rocks " of southern New Bruns- 

 wick show that in many cases the rocks represented as intrusive- 



