Revieics — Br. Mourlon — Geology of Belgium. 429 



(L. Landeilo). Lithologically they are quite distiBct from the type 

 specimens in the different collections of the American and Scotch 

 Laurentians ; while many if not all of them will be found in the 

 collections of the type specimens of the Huronian rocks. It is there- 

 fore evident it is not by litbological character that the age of the 

 older rocks of Donegal can be determined, but by careful field work 

 and examination of all the rocks between them and the fossiliferous 

 Cambro-Silurian near Pomeroy in Tyrone ; or, if King is correct, 

 of those between them and his fossiliferous rocks in Kilmaghrenan. 

 But this work must be more careful than that near Pomeroy, where 

 the fossiliferous Cambro-Silurian rocks are classified with those on 

 which they are deposited, although the latter were highly metamor- 

 phosed, upturned, contorted, faulted and denuded prior to the age 

 of the younger. 



Nothing as yet has been said by the Archaean geologists as to the 

 age of the older rocks near Bally castle, Co. Antrim, As however 

 they appear to be of the same age as those in the hills northward of 

 Pomeroy, Co. Tyrone, one age will have to be given to both ; it is 

 therefore necessary to mention them in a paper on this subject. 



E, Ei "V I E ATsT S. 



I , — Geologie de la Belgique. By Michel Mourlon, D.Sc, etc 

 2 vols., pp. 317 and 392, 2 Plates and 55 Woodcuts. (Brussels 

 Paris, and Berlin, 1880, 1881.) 



DE. MOURLON is well known as one of the most zealous 

 among the younger geologists of the Continent. Since 1870 

 he has published numerous papers, many of which — those on the 

 Devonian Rocks of Belgium, for instance — are of a high order of 

 excellence. He has been for some time actively employed on the 

 Geological Survey of Belgium, and the task of editing Andre 

 Dumont's manuscript notes — of which three large volumes have 

 already been issued — has been entrusted to him by his Govern- 

 ment. Dr. Mourlon moreover occupies the post of Curator in the 

 Natural History Museum at Brussels, and in the work under notice 

 we have further evidence of unremitting labour added to much 

 acumen and research. 



It is impossible to avoid comparing this new "Geology of Belgium " 

 with its able fore-runner, the Prodrome cVune description geologique 

 de la Belgique, by Prof. G. Dewalque. The latter was published in 

 1868, and at that date was thoroughly satisfactory. But the progress 

 of Geology during the last twelve years has been great — in Belgium 

 as elsewhere — and a second edition of the Prodrome had become a 

 necessity. Last year (1880) Prof. Dewalque surprised and disap- 

 pointed the scientific world by publishing, not a new and improved 

 edition of his valuable work, but a mere reprint of it, without 

 addition, omission, or change of any kind. Under these circum- 

 stances we are bound to welcome Dr. Mourlon's book as supplying 

 a greatly felt want, and we do so all the more readil^^ that it is laid 



