506 JS^otices of ITemoirs — Prof. Hull — Laurenilan in Donegal 



failing that, tlie mean temperature of the air did not rise to near the 

 freezing-j)oint. That such preservation of masses of ice is quite 

 possible is shown by their occurrence under the lava of Etna, and 

 often at the foot of cliffs under talus on which vegetation has after- 

 wards grown. 



If I understand rightly the published descriptions of the frozen 

 tundras, they are simply another instance of tlood deposits now per- 

 manently dry, through the lowering of the river-beds, in this respect 

 corresponding with the Ehine loess and probably with the Thames 

 Valley brick-earths. The whole country being formed of flood 

 deposits, it is not sui-prising that the bones are now constantly 

 found in hills much above the present river-level, for there appears 

 to be evidence that at the time of the formation of the Tundras, the 

 sea-level was a good deal higher than at present, the deposits on the 

 lower lands near the sea being marine or estuarine. When the fall 

 of the river was less than at the present day, the floods would neces- 

 sarily rise to a greater height. 



n^OTiciES oip nvcEnycoiias. 



I. — On the Laurentian Beds of Donegal and of other Parts 

 OF Ireland. By Professor Edward Hull, LL.D., F.R.S., etc., 

 Director of the Geological Survey of Ireland. 



AFTER a perusal of the writings of previous authors, and a 

 personal examination made in the spring of 1881, in company 

 with two of his colleagues of the Geological Survey, Mr. E. G. 

 Symes, F.G.S., and Mr. S. B. Wilkinson, the author had arrived at 

 the following conclusions. 



1st. That the Gneissose series of Donegal, sometimes called 

 "Donegal Granite," is unconformably overlaid by the metamor- 

 phosed quartzites, schists, and limestones which Professor Harkness 

 had shown to be the representatives of tbe Lower Silurian beds of 

 Scotland (Quart. Journ. Geol. Soc, vol. xvii. p. 256). This un- 

 conformity is especially noticeable in the district of Lough Salt, near 

 Glen. 



2nd. That the Gneissose series is similar in character and identical 

 in position and age with the " Fundamental Gneiss " (Murchison) 

 of parts of Sutherlandshire and Eoss-shire, and is, therefore, like the 

 latter, presumably of Laurentian age. Tliat the formation is a 

 metamorphosed series of sedimentary beds, had been shown by Dr. 

 Haughton and Mr. R. H. Scott. 



3rd. That the north-western boundary of the Donegal Gneiss is 

 a large fault between the Laurentian Gneiss and the metamorphosed 

 Lower Silurian beds, owing to which the older rocks have been 

 elevated, and by denudation have been exposed at the surface. 



4th. That the Cambrian formation of Scotland is not represented 

 in Donegal, and that the unconfoi-mity above referred to rej)resents 

 a double hiatus, and is of the same character as that which occurs . 



