Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/77

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on the northern. It offers no remarkable variety of composition, but appears to consist of various modifications of that syenite about to be described, to which on a former occasion I proposed that the name should be limited, the syenite connected with the trap formation. Those who are acquainted with the syenite of Arran, of which the main constituent is felspar, will recognize in this a similar rock, of which examples may also be found in the neighbouring island of Raasa, as well as in many other of the Western islands. The hill of Glamich may be selected as specimen of those which are formed of syenite and of clinkstone, both of which are in this case strongly marked, since, as already mentioned, the former displays its reddish yellow hue, and the latter a dark blue tint. In other respects there is no difference between these rocks in the general disposition, which is in both equally irregular and ill defined. I could not discover the contact of these substances, but am convinced from other observations that they are connected by a common bond of transition or of position, and that they present no essential differences in geological relations. As the syenite of this hill presents no peculiar varieties, and as the clinkstone has been already described, one common description of the former will serve for the whole group. There is probably cause for me to regret that I could, procure no more extensive access to the hills of this group, but the uninhabited and desart state of this tract of country renders it nearly impossible, since the limits of the longest day are insufficient for their examination, and since the storms and rains of this wild island form but a dreary canopy to its rocky pillow. I can therefore add nothing more precise to the general ideal I have already given of the connection of the syenite with the trap and with the clinkstone. The light coloured rocks which belong so the group appear in all cases to consist of the several varieties