450 



the directions of those extensive anticlinal and synclinal lines which 

 lie has determined with much personal labour, though unaided by 

 good geographical data. It will then be shown by him at what pe- 

 riods igneous action has been in operation within these older rocks ; 

 whilst it will be my province to point out how these outbursts have 

 been succeeded, on the eastern frontiers of the principality, by other 

 linear, submarine eruptions, and to describe the effects produced by 

 them upon the different sedimentary strata. 



These results must, however, only be viewed as the first attempts, 

 on the part of Professor Sedgwick and myself, to reduce to chrono- 

 logical order a vast succession of ancient deposits, which have hitherto 

 been much neglected in this country, on account, as we may suppose, 

 of the alleged obscurity of their organic remains, and still more, per- 

 haps, in consequence of their altered condition, due to the numerous 

 convulsions to which they have been subjected. 



Ireland. — We have been favoured with two communications upon 

 the geological structure of parts of the north of Ireland, illustrated by 

 excellent maps, constructed by the authors. In one of these, Mr. A. 

 Bryce, of Belfast, describes the north-eastern portion of Antrim, in 

 which he points out a much larger extent of mica schist than had 

 been noticed by former observers. These primary rocks are succeeded, 

 in ascending order, by ancient red conglomerates, partial carbonife- 

 rous deposits, new red sandstone, lias, greensand, and chalk. He 

 mentions porphyry as only associated with the older red sandstone; 

 and basalt, as overlying the chalk, all the important peculiarities of 

 which have been so well detailed by Conybeare and Buckland. 



The other Memoir upon Ireland is from the pen of Archdeacon 

 Verschoyle, and is much more comprehensive, describing the north- 

 west coast of Mayo and Sligo. The accompanying map is of consi- 

 derable value, the geographical features having been obtained from 

 the Ordnance surveyors ; chiefly, I believe, through the intervention 

 of Capt. Portlock, R.E. 



The Archdeacon shows that this region has for its mineralogical 

 axis a mountainous range of mica schist, and other primary rocks, 

 the overlying deposits consisting of partial conglomerates, succeeded 

 by the carboniferous limestone and unproductive coal measures, — the 

 former containing, as in many parts of England, a lower limestone 

 shale and an oolitic limestone. In describing the rocks of intrusive 

 character, this author is to be much commended for having traced, 

 with precision, the course of no less than eleven basaltic dykes, within 

 a zone of eleven miles in breadth ; which are parallel to each other, 

 trending nearly W. to E., and striking through all the rocks of the di- 

 strict — one of them being observable for the distance of 60 to 70 

 miles. 



With such works as these before us, we may feel assured that the 

 day is not far distant, when a manual of the structure of the whole 

 of our sister kingdom may be compiled. This useful work will doubt- 

 less be achieved by the efforts of the members of the new Geological 



