BRITISH ASSOCIATION MEETING AT NEWCASTLE. 
381 
one shore as to prevent the traveller landing, he is sure to find the other 
shore quite free from them.* 
Eepoet on THE Chemical and Mineral Composition of the 
Granites and associated Rocks of Donegal. By a Committee, con- 
sisting of Mr. Scott, Sir E. Griffith, and Professor Haughton. — The first 
, portion of the report contained a general description of the geological 
j features of the county Donegal, with an account of the difierent facts 
observed by the members of the committee during their various tours in 
I the county. It stated that in many particulars the non-granite rocks 
j of the county Donegal resembled those wliich are described by Mr. Mac- 
i farlane as characterizing the Huronian series of Canada and its Norwegian 
' equivalent the Tellemarken Quartz formation of Naumann, and the views 
put forward were supported by quotations from Mr. Macfarlane's papers 
in the ' Canadian Naturalist and Geologist ' for 1862, from the Reports of 
the Geological Survey of Canada, and from Keilliau's 'Gsea Norwegica.' 
One of the points on which considerable stress was laid by the authors of 
the report was the occurrence of " a chalcedonic conglomerate, of which 
the cement is micaceous and the pebbles are mainly siliceous of tbe chal- 
j cedonic variety, but consist also of pieces of the mica-schist itself, and 
j sometimes also of feldspar." This rock is an extremely characteristic 
I feature of the north-east of the county Donegal, and may perhaps be 
found to be present in a corresponding position in Scotland, as it would 
appear that conglomerates of a similar nature have been observed by Sir 
H. Griffith at Anie, in the neighbourhood of Callander, and by Professor 
Haughton at the summit level of the Crinan canal. The igneous rocks, 
which are very abundant in the county, were found to be regularly inter- 
stratified with the grits seen in Limshowan, while in the south of the county 
rocks of a similar constitution were found to be intrusive. Analyses of 
both varieties were given in the Report. The coarse-grained varieties of 
I these rocks were all termed by the authors syenites, as they class under 
the generic term syenites all rocks which consist mainly of a hornblendic 
mineral associated with a feldspar, and with a quartz or mica, or both. 
This term includes diorite and other rocks whose nomenclature seems at 
present to be not quite fixed, as the names are used in different senses by 
different authors. Limestone was found in considerable abundance ; no 
! fossils have been discovered in it, and it passes into crystalline marble in 
the neighbourhood of the granite. As to the granite it-self, it contains 
the two feldspars orthoclase and oligoclase, with black mica, quartz, and 
almost universally small crystals of sphene. In some varieties of the rock 
it is so abundant as to induce the authors of the report to term it sphenic 
granite. This mineral has been long known to exist in the granite of 
parts of Scotland, and it is also found in that of Galway. Evidence was 
adduced to show the gneissose character of the granite when seen in the 
i field, and its passage by insensible gradation into gneiss and mica-schist 
! in a manner precisely similar to that described by Keilhau as having been 
' observed by him in Norway. In addition to this fact, attention has been 
drawn to the stratified nature of the granite, and to the occurrence of 
gneiss and of limestone in several localities within its area. In such cases 
the limestone is extremely rich in minerals, and is generally accompanied 
by a peculiar rock, called by the authors " sphene rock," which consists of 
orthoclase, quartz, and pyroxene, with sphene in extreme abundance ; and 
a quotation was made from the Canadian reports before referred to, to 
show that a similar connection of these rocks had been observed in Ca- 
* See also for the subject, ' Geologist,' vol. i. p. 539 (1838). 
