2 The Irish Naturalish January, 



tion on the possibly allied genus Monocratermi to the Irish 

 Naturalist for the same year, p. 135. 



THE MEJTAMORPHIC ROCKS OF NORTHERN IREI<AND. 



Prof. Cole {Trans. R. Irish Acad., vol. xxxi., 1900, pp. 431- 

 472), discusses the characters of the gneissic axis and asso- 

 ciated green rocks of Tyrone. The latter are an igneous series, 

 penetrated by granite of the Slieve Gallion type. Though 

 imitations of gneiss on a small scale are produced at Creggan- 

 conroe by the parallel intrusions of this granite in a diorite 

 of the " green rock " series, yet the central gneiss does not 

 seem to have arisen from the attack of this particular granite 

 on the overlying rocks. While the old gneiss is probably 

 itself a composite rock, yet it was solidified at a very early 

 date, as is shown by fragments torn from it and included 

 in the granite of Fir Mountain. The author regards this 

 granite as probably connected with the Caledonian or post_ 

 Silurian earth-movements. 



Having thus sought to show that the central gneiss of Bast 

 Tyrone owes its banded character to the intrusion of a pre- 

 Caledonian granite into still older basic schists, the author 

 passes to the area between Pettigo and Donegal Town, where 

 the Dalradian rocks have been described by the Survey as 

 resting on an older gneissic group. He believes, on the other 

 hand, that the gneisses of South Donegal have intruded into 

 the Dalradian series, of which they retain fragments in all 

 stages ot absorption. The Dalradians are thus the oldest 

 known rocks in that part of the country. The whole complex 

 group, including the granite, which has formed gneisses by 

 its igneous flow and parallel intrusion, is probably of 

 Archaean age. The paper is illustrated by six reproductions, 

 in colour, of drawings by Mrs. Cole, made from microscopic 

 sections, and by photographs of rock-structures. 



Two years later {Proc. R. hish Academy, vol. xxiv., 

 section B, pp. 203-230), Prof. Cole emphasises the above con- 

 clusions in a paper on "Composite Gneisses in Boylagh, 

 West Donegal." This is mainly a petrographic essay on the 

 production of gneiss by the intrusion of granite into rocks 

 which already possess a parallel structure. In Donegal such 

 rocks are provided by the Dalradian series, which retains 



