1913. Irish Societies, 39 
Cookstown. He also showed slides of the three types of basalt which 
occur in Scrabo quarry, of the coarse-grained basalt from the probable 
volcanic neck at Bally money, near Holy wood, and of the basic dyke in 
Kilcoan quarry, Island Magee. 
Dr. DwERRYHOUSE exhibited slides of epidiorite and hornblende - 
schist from the Loch Assynt district of the north-west Highlands of 
Scotland. 
Miss M. D. Mitchell and Miss Rea showed a micro-section of a 
siliceous oolite from the vicinity of the State College, Pennsylvania. 
Mr. Maxwell exhibited slides" of Irish marbles, New-ry and Mourne 
granites, nummulitic limestone, and coal ; also a micro-section, showing 
fossil cellular structure, leaves and rootlets. Diatoms, Foraminifera, &c., 
were included in his exhibit. 
Robert Bell showed interesting hand specimens, including a very 
large Pleurotomaria from the Chalk of Moneymore, chalcedoney from 
the same district, and phacolite from Craig-a-heilliar, Portrush. 
Sylvanus Wear's exhibit included line slides made by himself of 
local basalts and dolerites, and asbestos from Ligoniel. 
Miss M. K. Andrews showed microscopic sections of rocks from 
the Mourne district, also of a diabase dyke at Scawt Hill, remarkable for 
its beautiful pleochroic augite, and a slide of the adjoining chalk com- 
pletely altered into a calc-silicate hornstone. 
December 17. — Arthur R. Dw^erryhouse d.sc, f.g.s., m.r.i.a. 
lectured on "' Some Geological Features of Scotland and their Relation 
to the Structure of the North of Ireland." The lecturer directed his 
attention chiefly to the Archaean and older Palaeozoic rocks, as the great 
"Caledonian" earth-movements v/hich above all others determined 
the structure of the North of Ireland took place at the end of the Silurian 
period. The structure of the North West Highlands of Scotland was 
dealt with at some length, and it was shown that the i.ew-isian gneiss, 
the oldest rock known in the British Isles, had been formed b}' the crushing 
and shearing of a great complex of basic igneous rocks. The sequence of 
events prior to the deposition of the Torridon Sandstone was shown to be 
a complex and lengthy one, including {a) the intrusion of the igneous 
rocks ; {h) their conversion into gneiss by mechanical deformation ; (c) 
the intrusion of four sets of igneous dykes ; (d) further earth-movements 
which converted the d^-kes into epidiorites, hornblende-schists, mica- 
schists, (fee. ; {<?) great denudation of the land-surface, which removed 
the cover under which the igneous rocks and gneisses had been formed. 
The formation of the Torridon Sandstone was folio w^ed by earth -move- 
ments and extensive denudation, and later by a downward movement 
of the land, which sank beneath the level of the sea in which the Cambrian 
rocks were subsequently deposited. At a later date after the formation 
of the Ordovician and Silurian rocks a still more stupendous series of 
earth -movements set in, producing the enormous thrust-planes and reversed 
faults so characteristic of the North-West Highlands. Attention was 
drawn to the natural division of Scotland into four great structural areas — 
viz. (I) the North-West Highlands ; (2) the Eastern and Central High- 
