Reviews — Prof. E. HuWs Geology of Ireland. 557 



rocks of north-west Donegal were of Arcligean age, " this view, 

 for which there is much conflicting evidence, I have been obliged to 

 abandon." We think the author is right in using the term Archgean 

 as a general group-name for rocks considered to be Pre-Cambrian ; 

 but he makes no reference to the term " Dalradian " (derived from 

 the old kingdom of Dalriada in the north of Ireland), that has lately 

 been suggested by Sir A. Geikie for the crystalline schists of the 

 north of Ireland and the centre and south-west of Scotland. Already 

 Prof. Hull's remarks on the " Lower Silurian " rocks of Donegal 

 may need revision. 



In his account of the Old Red Sandstone the author employs the 

 name Devono-Silurian for the Glengarifif Grits and Dingle Beds, 

 which he regards as equivalent to the Downton Sandstones of 

 Hereford and the Foreland grits and slates of North Devon. These 

 beds are surmounted unconformably by the Upper Old Red Sand- 

 stone, and thus there is a great gap that may be elsewhere repre- 

 sented by the Middle Devonian. 



Indications are given of the zones in the Carboniferous Limestone, 

 for the recognition of which the labours of De Koninck are 

 acknowledged. 



Some criticisms are called for by the Table of Formations given 

 on page 3, for the " Liassic group" is separated from the '-Oolitic 

 or Jurassic group." Hence the author is led to remark that the 

 vi^hole of the Jurassic series is unrepresented in Ireland, whereas 

 it is customary to include both Lias and Oolites in the Jurassic 

 system. Again he has given in upward succession above the Oolitic 

 or Jurassic group, and ranged in similar type as if equivalent in 

 value, the Purbeck Beds, Wealden Beds, Neocomian Beds, and the 

 Lower Cretaceous Beds ; a very unfortunate grouping to say the 

 least of it, although it is true that these formations are simply noted 

 for the sake of comparison with those represented in Ireland. 



The author criticizes the view (put forward by Sir A. Geikie) 

 that the trachytes and pitchstones of Antrim are far younger than 

 the surrounding basaltic sheets, and he refers to the occurrence of 

 numerous pebbles of Tardree trachyte in the stratified ash-beds 

 ■which overlie the lower basaltic sheets in certain localities. 



The Pliocene age of the clays of Lough Neagh is still maintained 

 by the author, although the occurrence of " bivalve shells resembling 

 a species of Unio, or Mytilus," cannot be said to count for much. 



A good description of the Glacial Drifts follows. I'hese include 

 Lower Boulder-clay, Middle Sand and Gravel and Upper Boulder- 

 clay. "The Lower Boulder-clay is the most extensivel_y distributed 

 of all the Post-Pliocene deposits in Ireland." It is a stiff clay with 

 striated blocks. The "Middle Sand and Gravel" is stated to contain 

 marine shells in various places, and "may be regarded as a formation 

 of marine origin, which has been strewn over the bed of a com- 

 paratively shallow sea." Yet we find it at elevations of 1300 feet. 

 The author is disposed to think that floating ice may have had 

 something to do with the accumulation of some of these gravels ; 

 but he is led to infer a great depression, which must have reached 



