BRITISH ASSOCIATION MEETING. 
537 
tious. Ill some parts there were broken bands of coal, thrown about in an 
extraordinary way. The whole of the highly-inclined strata were surmounted 
by new red sandstone. It was remarkable that there was in this cutting an 
enormous amount of calcareous and other grit, some bodies of wliich miglit be 
supposed to have formed a regular part of the mouutahi-limestone. Tliere 
were also l-?.rge masses of red substance, evidently fonued by concretion. 
OX THE GRANITE-ROCKS OF DONEGAL AND THE MINERALS 
ASSOCIATED THEREWITH. 
Bv R. H. Scott, Esq. 
The author gave a short account of a mincralogical tour made by him, in 
company with Prof. Haughton, the result of which seemed to throw sos;!e 
light on the possible origin of granite. The dishict visited was Donegal, 
wliich county consists mainly of gneiss and mica-slate, and is traversed in a 
north-east direction by an axis of granite. This granite is of a peculiar com- 
position, coutainiiig two felspars, one orthose, but the otiier not alljite, as in 
the granite of the Morn? mountains, but oligoclasc — a mineral whose oeeui- 
rence in the British Ishinds liad only l)een noticed Avithin tlie last twelve; 
months. Prof. Haughton, to whom this discovery is due, vras unfortunately 
unable to attend tlie meeting. The facts were brietly these : — The granite 
contains oligoclasc and quartz, which combination appears to be a proof tliut 
the rock never was in a melted condition; as in that case these two minerals 
would liave acted on each other and formed common felspar. It lies in beds 
corresponding to the general lie of the strata of the country, and in its cha- 
racter is essentially gneissose ; and, lastly, at points inside rhe area of the 
granite, metamorphie rocks (limestone and slates) are found with their bedding, 
which is nearly vertical, unchanged. These bands run for a distance in one 
case of nine miles across the country. The condition of these rocks is very 
similar to that of the same rocks outside the granite area; and it is a point of 
great interest to determine how they got there. The solution of this offered 
by tlie author of the paper was that the whole of the rocks had been originally 
stratilied, and had been subjected to some actions which had been termed 
metamorphie. The result of such action was to convert some into granite, 
some into gneiss, and some into crystalline limestone and mica-schist, without 
very much altering their relative i)ositions. Tlie possibility of granite being 
jiroduced by other means than simple heat seemed to then to be ])roved by 
the occurrence of felspar in quartz-veins, which are usually admitted to have 
been tilled by means of infiltration. There were several points in connection 
with these granites which showed a close relation between them and the gra- 
nites of Norway. The whole question required a careful chemical and mincr- 
alogical examination, which could not be concluded for some time. Among 
the types of rock found in Donegal is a syenite, the felspar of which is oligo- 
clase. The origin of this rock the author is disposed to attribute to the addi- 
tion of limestone to the granite. A similar svenite occurs at Carlingford, but 
contains anorthitc, a felspar which would result from the admixture of a larger 
quantity of limestone than is necessary to produce oligoclasc, and has beeii 
proved by Prof. Haughton to have such an origin. The anorthitc- yenite never 
occurs unless limestone is present in large excess, which is not the case in 
Djueg il. The district described is very ricli in minerals, sorn.^ extremely rare. 
VOL tv. 
3o 
