Gairloch In North-West Ross-Shire Part 41

*L. litorea.

*L. rudis.

*Do. do., _var._ saxatilis.

*L. neritoides.

*Rissoa violacea.

*Do. do., _var._ ecostata.

R. semistriata.

*R. striata.

*Do. do., _var._ arctica.

*R. parva.

*Do. do., _var._ interrupta.

R. punctura (a fragment).

*R. cingillus.

*Hydrobia ulvae.

Do. do., _var._ albida.

*Skenea planorbis.

Cc.u.m glabrum (one specimen).

C. trachea (one specimen).

Odostomia rissodes.

O. indistincta.

O. lactea.

*O. nitidissima.

*Natica Alderi.

Velutina laevigata.

*Aporrhas pes-pelecani.

*Cerithium reticulatum.

*Purpura lapillus.

Do. do., _var._ imbricata.

Buccinum undatum.

Fusus antiquus.

*Na.s.sa incra.s.sata.

Do. do., _var._ minor.

Pleurotoma striolata (one specimen).

*Cylichna umbilicata.

*Utriculus truncatulus.

U. obtusus.

*U. hyalinus.

U. mammillatus (two specimens).

Philine catena.

P. angulata (one specimen).

Melampus bidentatus.

Spirialis retroversus.

The following are a few notes on the land and fresh-water sh.e.l.ls:--

Pisidium fontinale--Occurred in the sh.e.l.l-sand, having been washed down to the sea by streams. I found a fine variety--perhaps _var._ pulch.e.l.la--in a pond between Gairloch and Loch Maree.

Ancylus fluviatilis--Several among the sh.e.l.l-sand.

Succinea putris--Two among the sh.e.l.l-sand.

Vitrina pellucida--Not uncommon under stones, &c.

Zonites cellarius--Two among the sh.e.l.l-sand. I found it also living among stones.

Zonites nitidulus, _var._ nitens--Living among stones, &c.

Zonites purus--Among dead leaves.

Zonites radiatulus--Two among the sh.e.l.l-sand. It is probably not rare under stones, &c.

Zonites fulvus--Among dead leaves.

Helix nemoralis--Among the sh.e.l.l-sand.

Helix rotundata--Under stones.

Pupa umbilicata--Under stones. The variety edentula occurs.

Balia perversa--Common at the foot of walls near the parish church, and probably in other places.

Clausilia rugosa--Under stones, &c.

Cochlicopa lubrica--Three among the sh.e.l.l-sand.

J. M'MURTRIE.

Chapter IX.

THE GEOLOGY OF LOCH MAREE AND NEIGHBOURHOOD.

By WILLIAM JOLLY.

The geology of Loch Maree is unusually varied, interesting, and representative. It exhibits, in a limited area, the whole debated series of the succession of rocks in the North-West Highlands. This has been a fertile subject of controversy, surpa.s.sed only by the world-famous Glen Roy. It has engaged the attention and the pens of some of the most eminent British geologists, including Macculloch, Hugh Miller, Sedgwick, Sir Roderick Murchison, Professor Nicol of Aberdeen, Archibald Geikie, and a host of others not less able. After considerable discussion, chiefly between Murchison and Nicol, the authoritative name of Murchison, along with that of Archibald Geikie, who wrote a joint memoir on the subject, seemed for a time finally to settle the question in Murchison's favour; and his views were not only generally received, but were embodied in the geological maps of the district most in use. But, lately, the whole question has been reopened with greater keenness than ever, and the conclusions of the geological king have been vigorously and uncompromisingly a.s.sailed all along the line. The war is, at the present date, in full swing, but with a near prospect of final peace.

The geological problem of the Highlands is by no means settled, though much additional light has been thrown on the debatable ground by the researches of the numerous and capable combatants, including recently Peach and Horne, of the Geological Survey; and their investigations will no doubt hasten the final determination of the vexed question. But a firm basis of interpretation has at length been gained, by which the geological structure of the broad tracts of the Highlands, hitherto uniformly coloured as Silurian, will be investigated under new and important lights, and a remapping of the Highland area erelong achieved, with such permanent results as have hitherto been impossible.

The conditions of the problem are extremely well exhibited round Loch Maree. Here we are presented, as Dr Archibald Geikie truly observes, with "a series of sections of singular clearness." He confesses that he knows of "no locality where the geologist may better acquaint himself with the order of superposition of the ancient crystalline rocks of the Highlands, or with the dislocations and metamorphism which they have undergone." These will now be briefly explained. The whole subject may, without much difficulty, be understood by the ordinary reader, if he will use a geological map of Scotland, such as Nicol's or Geikie's, which he will also find useful as a guide.

A.--THE SERIES OF ROCKS IN THE NORTH-WEST HIGHLANDS.

The rocks round Loch Maree are shortly the following:--

I. THE HEBRIDEAN GNEISS.--The Long Island from the b.u.t.t of the Lews to Barra Head consists almost entirely of a species of gneiss, very much metamorphosed. It occurs in the Inner Hebrides in Tiree and Coll, in Sleat, in Raasay, and Rona, off Portree, but very little in Skye, one of our youngest isles. It is found in patches on the Mainland on the western sh.o.r.es of Ross and Sutherland, and stretches from Torridon to Cape Wrath, whose contorted cliffs it forms. It has been variously designated _Hebridean_, from being chiefly found in the Hebrides; _Lewisean_, from forming the most of the Lewis, a less acceptable name; _Archaean_, from being the earliest system; _Pre-Cambrian_, as being earlier than the Cambrian sandstone immediately above it; and _Fundamental_, from its const.i.tuting the lowest rock strata in the British Isles. Murchison identified it with the lowest geological series, the _Laurentian_, which is so named from being extensively developed on the St Lawrence in Canada. It is best, however, to designate the rocks by a geographical and non-theoretical term, like Hebridean.

This gneiss is more largely exhibited on the sh.o.r.es of Loch Maree than any other rock, forming the greater part of its northern side from the exit of the Ewe to Slioch, and running along its southern side from near Inverasdale on Loch Ewe to Talladale. It stretches northwards from the lake to Loch Gruinard, and westwards to Poolewe and Gairloch, where its characteristics are very well seen on the wave-beaten coast near the hotel there. It forms the rugged outlines of Craig Tollie, at the west end of the loch, and of Beinn Aridh Charr and Beinn Lair, near Letterewe. It shows one of the most magnificent series of furrowed precipices in Britain, at the back of Beinn Lair, which should be visited by all who appreciate the wildly grand; and entirely encloses the lone Loch Fionn and its darker chamber of the Dubh Loch at its head.