in the durability of these mountain greenstones and those of the stratified trap, or of forming any probable conclusion respecting their æras of formation. Much remains to be learnt before we can attain to an accurate knowledge of these rocks, and there is much yet remaining for future observers in the ground which I have now trodden. But it is not an easy task to ascend these pinnacles and to traverse this rocky desart even in summer, and summer seems never to shine on them—at least it has never yet shone for me.
I must now proceed to consider the last rock which remains described, the Syenite.
In describing the Cuchullin, I have for the sake of contrast introduced so many of the most remarkable features of the other group, which I have distinguished by the name of the Red Hills, that the less will remain to be said respecting them. They are invariably characterized by the lumpish roundness of their outline. The cause of this consists evidently in their rapid decomposition, and in the accumulations of fragments which cover not only their sides but their summits so completely, as to preclude in most places any view of the naked rock. Their elevation I have formerly observed is much less than that of the Cuchullin, and I have also remarked that they form a separate assemblage, interfering at their bases only by indentation or approximation, and being always distinguished from the latter both in character and composition. The summits most convenient of access are those of Ben-na-Caillich near Broadford, with its dependencies, and the somewhat insulated mountain of Glamich above Sconser, the highest of the group. As Ben-na-Caillich presents the greatest simplicity of composition, I will describe it first. It forms part of a group which descends into the plain by various acute ridges, reaching into Strathmore and the head of Loch Slapin on the southern side, and extending towards Scalpa
