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.* 



Repokt on the Chemical and Minekal Composition of the 

 Granites and associated Rocks of Donegal. By a Committee, con- 

 sisting of Mr. Scott, Sir R. Griffith, and Professor Haughton. — The first 

 portion of the report contained a general description of the geological 

 features of the county Donegal, with an account of the different facts 

 observed by the members of" the committee during their various tours in 

 the county. It stated that in many particulars the non-granite rocks 

 of the county Donegal resembled those which are described by Mr. Mac- 

 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 Keilhau'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 the chal- 

 cedonic variety, but consist also of pieces of the mica-schist itself, and 

 sometimes also of feldspar." This rock is an extremely characteristic 

 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 

 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 itself, 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 

 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 (1858). 



