Reports and Proceedings. 73 
on the Geology of some of the Western Islands of Scotland. He said 
that the following brief notes, mineralogical and geological, made 
during a yachting-cruise in the West of Scotland, on board Mr. 
Graves’s yacht ‘lerne,’ in the summer of 1864, may be of the more 
interest to the R. Geol. Soc. of Ireland, in consequence of the close 
relation between that part of Scotland and the North of Ireland. 
Crystalline White Limestone of Iona.—On the 17th of July we 
visited the metamorphic white limestone of Iona, described by 
Jamieson and others. It bears N. 15° E. by compass, and dips 
80° E., and is from 40 to 50 feet in thickness. “Tt is pure white, and 
has a remarkably flaky appearance, fully explained by its mineralo- 
gical composition. On being analyzed, it was found to consist of 71 
per cent. of dolomite, and 29 per cent. of a silicate, which proved to 
be a var riety of tremolite. At the time of our visit it was nearly 
high water, and we were therefore unable to examine that portion 
of the limestone, exposed at low water, which is said to pass into 
“verde antique,’ of which, indeed, we found several rolled pebbles on 
the strand. Labradoritic Syenite of Loch Scavig, in Skye.—We 
visited the remarkable mountains that surround this wild loch on 
the 3rd of August, and brought away with us very good specimens 
of the syenite of which they are composed. ‘The mass of the rock 
is a medium-grained syenite composed of augite and labradorite, and 
was particularly interesting to me, because I had failed to find this 
rock in Donegal, although there are specimens, collected by the late 
Mr. Townsend, C.E., probably from Donegal, in the Geological 
Museum of Trinity College. Beds of metamorphic rocks, in which 
labradorite forms an essential constituent, are well known to form 
an important part of the Laurentian system in Canada, and I was 
therefore glad to have an opportunity of examining a similar rock 
in situ in Scotland. The syenite is bedded, and evidently meta- 
morphic, and is penetrated frequently by dykes of similar syenite, 
sometimes finer, sometimes coarser in the grain. In the coarsely 
crystallized masses, the labradorite and augite acquire large dimen- 
sions, and are associated with a considerable quantity of ilmenite, 
such as is found in the oligoclasic syenite of Horn Head, in Donegal. 
—— Granite of Ross of Mull.—On the 17th of July we visited the 
celebrated granite-quarry of the Ross of Mull, from which it was pro- 
posed to obtain the monolith in honour of the late Prince Consort. 
The granite is coarse, with quartz abundant, and only one felspar, 
namely, a pink orthoclase, with a little black mica. Its analysis 
shows that it differs much from the granite of Strontian,* two 
analyses of which were published by me in the ‘ Quarterly Journal 
of the Geological Society of London,’ in Part IV. of my ‘Experi- 
mental Researches on the Granites of Ireland.’ Gryphea-beds of 
Loch Aline.—On the 15th of July we visited these beds, and found 
them to consist of decomposing dark beds of shaly limestone, at the 
* One of these granites is published, on the authority of Sir R. Murchison, as 
from Tobermory ; but I believe it was originally a specimen from Strontian, and 
was brought to Tobermory as a building-stone. 
