72 



Guide to Belfast. 



" 5th. The black shales and associated flags at Tieve- 

 shilly, near Portaferry, occupy either the extreme top of 

 the Middle, or the base of the Upper Silurians, and are 

 the highest Silurians yet recognised in the north-east of 

 Ireland. 



" The geographical relation of the area under considera- 

 tion to that of South Scotland, and the general direction of 

 the strike of the rocks in both districts, would naturally lead 

 to the expectation of a certain degree of similarity between 

 their geological characters. From the foregoing, however, 



VERTICAL STKATA, ARDGLASS. 



it is clear that not only generally, but in detail, do they cor- 

 respond in a remarkable degree. While it would, perhaps, 

 be impossible, owing to the imperfect manner in which the 

 fossil bands are exposed, to unravel the sequence of the 

 various bed in County Down from an examination of them 

 alone, the key afforded by the recent researches in the 

 Scottish beds has made the subject a matter of ease. 

 We are thus enabled for the first time, with some 

 amount of certainty, to arrive at conclusions regarding 



