In the Western Islands, serpentine occurs in the island of Scalpa, the scat of the lighthouse crn the C3St coast, and also on the neighbouring shore, of Harris. Otherwise, it does not appear to have been observed in the islands, if we except quantities ex ceedingly trifling in Iona and Sky.
On the west of Sutherland, it occurs in three or four places, dispersedly, and in very small quantities, interstratified with gneiss; and here also, as in Scal pa, it is without beauty. That of Portsoy next conspicuous mass known ; and it is familiar from having been long, though scantily wrought. In early times it was exported to France; and ornamental archi tecture from it is said to be still existing at Paris. It is not now encouraged; though, from its very great variety and beauty, and from the facility of quarrying and shipment, it might be rendered profitable, as well as ornamental, were it to obtain a fashion. Geo logically speaking, it seems to be interstratified with the slate, gneiss, and quartz rock of the same locali ty; but it is not easy to ascertain this satisfactorily, as it appears in itself to be but an irregular mass.
In Aberdeenshire there are numerous independent masses of serpentine scattered about the country; but the greatest number of them are very small; and none are extensive. They are, in some cases, singularly connected with granite, and at others appear to be short strata, including schistose rocks. The masses near Kildrummie and Glen Kindle seem the most ex tensive, and they afford considerable quantities of as bestos. Serpentine also occurs in connexion with trap, and otherwise, on the confines of the mountains of Angus; and at Clunie in Perthshire it presents the rare and interesting phenomenon of a transition into trap, forming the sides of a vein of that substance. The last mass of this rock which we' are acquainted with in Scotland, is found on the west coast, between Girvan and Ballantrae.
Chlorite schist is so little distinct in general from micaceous schist, that we have not thought it worth while hitherto to distinguish the two ; but we cannot help pointing out to geologists a singular series of this rock on the west coast of Argyllshire; although, as the details are too minute for our article, we must refer to the work on the Western Islands formerly named, where there is a somewhat minute descrip tion of it.
It remains to point out the primary limestone of Scotland, which are, like some other rocks, so dis persed, and in such minute quantities, that we scarce ly know how to refer to them, but shall, as usual com mence with the Shetland Islands.
They are here very numerous, though seldom ex tensive; being interstratified with the other primary rocks, and found in almost every place. The largest apparent mass in one place is that at Stromness Voe;. and next in importance are those of Tingwall, the Outskerries, and a few other places, for which it will be best to refer, as usual, to Dr. Hibbert. The geo logical appearances are sometimes interesting, parti cularly in Burra, and in other places where granite occurs : but they precisely resemble those of Glen Tilt. Economically speaking, Shetland has not yet derived the advantages from its limestone, in agri culture, which it might have done; but that is not to be wondered at, where this art is so backward, and encumbered with so many political and physical im pediments.
In the Western Islands primary limestones are rare. With exceptions too trifling to name, they are found only in Lismore, Tirey, Iona, the Garveloch isles, and Isla. The marble of Tirey is familiar; but the work ing of this quarry has long been abandoned for want of a demand. It is a lump lying in gneiss, and is at tended by a similar one of a beautifully white marble, often spotted with green, hitherto unnoticed. The white marble of Iona is equally well known; but it has long been exhausted. We already noticed that of the Garveloch isles as a possible branch of com merce; and need only here add, that it is accompa nied by mica slate. We also mentioned that of Lis more at the same time; but this variety is of no beauty, being blue, and interstratified with clay slate, as are the corresponding strata in Appin. In Isla the limestone forms an extensive tract, and is noted for containing lead mines, which were formerly wrought.