Essay contains many interesting descriptions of the relations of the strata, but is singularly defective in its references to organic remains. Yet the author somewhat unguardedly observes -"If geologists have in the course of their investigations come to any certainty concerning the ancient state of our globe, there is certainly no one doctrine supported by a greater number of facts than that of progressive development !!"— Wern. Mem., vii. 3.

The last of the treatises illustrative of the geology of Edinburgh, which we shall notice, is Mr Maclaren's important "Sketch of the Geology of Fife and the Lothians," Edin. 1839. It abounds with detailed descriptions of the rocks of the neighbourhood, accompanied by sections and diagrams of the more interesting phenomena, and has aided, to a very great extent, the researches of the private student. In too many instances, however, the author has indulged in hypothetical explanations, and has, in a great measure, overlooked the organic contents of the strata. The work has been for some time out of print, and a new edition, believed to be in the press, has been long and anxiously looked for.

In addition to these communications, we may mention that several references to the lithology of Edinburgh occur in the writings of Faujas Saint Fond, Webster, Boué, L. A, Necker De Saussure, J. Nicol, and others. To the observations of these authors we shall endeavour to do justice, as opportunity offers.

From the preceding remarks, the reader may be disposed to conclude that our knowledge of the lithology of the neighbourhood of Edinburgh is extensive, that the subject has been handled by many intelligent observers, and that very little remains to be done, except perhaps to collect and arrange, in a more convenient form, the observations which have been already secured. This, however, would be a very inconsiderate conclusion, for the very same remarks which fell from the pen of Mr Allan thirty-five years ago, are at the present moment as applicable as ever. "It may be thought that the subject is exhausted. But this is an error I am very desirous to com

bat, not only because, in my own experience, I have found it to be one, but because, as science advances, our habits of investigation improve, phenomena become more familiar, we learn to trace and to secure not only the objects we are in pursuit of, but also to detect others which our less practised eye had originally passed over unnoticed." We all think ourselves perfectly acquainted with the rock on which our Castle stands. But I suspect there are many members of this Society who will be surprised to learn that sandstone occurs near its summit and also at its base. Salisbury Craig and Arthur Seat appear perfectly familiar to us; there are phenomena belonging to both, however, of which, I have no doubt, many are yet ignorant."-Edin. Trans., vol. vi.

Considering the length of time during which mineralogy, petralogy, and palæontology have been taught in the class of Natural History, the state of our public collection is far from satisfactory. Until a very recent period, the MUSEUM did not furnish the student with adequate resources, but exhibited, rather, attractive specimens from distant localities. The late lamented Professor E. Forbes, during his brief occupancy of the Chair of Natural History, began to collect and exhibit specimens illustrative of the petralogy of the neighbourhood, and the organic remains in our rocks, especially those belonging to the animal kingdom, would speedily have occupied his attention. There is good ground to hope that his successor in office will follow out those views which he so unequivocally expressed and laboured so enthusiastically to accomplish. The vegetable organisms of the strata around Edinburgh are beginning to attract some share of attention, and the collection which Dr Balfour has already formed in the Museum of the Botanical Garden is calculated to aid the researches of the young palæontologist.

The SCIENTIFIC SOCIETIES of Edinburgh have to a considerable extent contributed to the progress of Edinburgh Lithology. The Royal Society has always given a certain amount of encouragement to local inquirers. The Wernerian Natural History Society, now extinct, was for several years in active

operation. The Transactions of these two Societies have already been referred to, and several of the papers which they contain are of great interest. The Royal Physical Society now occupies the field which the Wernerian Society was wont to cultivate, and has given indications of a useful career.

There is yet another institution to which the lovers of Lithology in Edinburgh may reasonably look forward, as destined to advance the interests of their favourite science the INDUSTRIAL MUSEUM. It is a matter of deep regret that, for the present, the funds necessary for its progress and usefulness have been ungraciously withheld. But the common sense of the public will, ere long, recognise the value of such a collection as calculated to advance the interests of society. Meanwhile, we trust that the GEOLOGICAL SURVEY will be preparing to furnish its invaluable contributions. Its staff of efficient observers, and equally active collectors, may be looked to for speedily furnishing more trustworthy results, respecting the distribution and contents of the rocks, than can be expected from private and uncombined exertion.

B

18

CHAPTER II.

Origin of the picturesque scenery around Edinburgh-Valleys, Ridges, Bays, and Nesses-Valleys of abrasion and their bifurcation—Rivers, Reaches, Craig, and Tail.

THE remarkable irregularity of the ground in the neighbourhood of the city, and the equally varied aspect of the sky-line in every direction, have long attracted the notice of the lovers of landscape, and usually excite in the breast of strangers a feeling of intense admiration. But the eye, which has enjoyed a geological training, is enabled, besides being gratified by the same picturesque scenery, to detect groups of interesting phenomena well fitted to excite reflections of a more intellectual kind. The abrupt faces of the rocks, the inclination of the beds and their fractured contents, indicate a violent disruptive force acting from below, while a different agency has spent its fury on the surface, removing or assorting the softer materials, leaving the harder portions, the protuberances, ridges, or hills, as an index of the devastation which has occurred.

Before, however, entering upon the details of the surface inequalities of the district, I shall take liberty to remark, that much difference of opinion prevails respecting the character of the forces which have been in action, their origin, and the direction in which they have exerted their influence. Hence it is expedient, where practicable, to attend to some of the more obvious but too much neglected elementary truths, that aid in observing the phenomena satisfactorily, and test the explanations which have been offered.

of

When we examine a VALLEY of any extent with the eye a petralogist, it will be found generally that the rocks existing in the trough, are softer and more easily acted upon by air and water than those which form the bounding ridges. Interspersed

portions of harder rock may be occasionally found among the softer materials, but these will merely cause inequalities in the valley, and mark, by their elevation, the resistance which has been offered to the disintegrating forces which have reduced the contiguous portions to a lower level. The valley of St Leonards, the North Loch, and that of the Hunter's Bog, may here be quoted as illustrative examples.

When we examine a BAY, or indentation on the coast, we generally find analogous appearances. The softer beds have been acted upon, broken up and removed by the action of the ripple of wind or storm waves, while the harder materials remain and constitute those promontories or NESSES, which form the lateral limits of the recess or creek. Even in the bay, as in the valley usually connected with it, certain portions of harder rock may have existed, and such will usually be preserved as islets or skerries, to mark the abrasion which has taken place around.

The young petralogist may witness very distinct evidence of this view of the formation of bays at Granton or Trinity. At either of these places the beds of sandstone resist the abrading agency of the sea ripple far more successfully than the softer beds of argillite or shale with which they are interstratified Hence all the hollows on the beach, or indentations at the sea margin, can be successfully referred to their forming agent, acting readily on the shale, but withstood more or less by the sandstone. Indeed, the promontory of Joppa, the ridge of the Black Rocks at Leith, and the projecting portions of the shore at Granton, may be studied with advantage as illustrative examples. The islands of the Firth of Forth give likewise unequivocal indications of the resistance offered by the harder rocks, which, in general, in this quarter, belong to the trap family. Thus the Bass, May, Inchkeith, Inchcolm, Inchgarvy, and others of minor bulk, plainly indicate the extent of abrasion which has taken place, and the means of their preservation. Irrespective of the groups of rocks in the immediate neighbourhood, which we shall soon consider in detail, the spectator, looking around from the Castle, the Calton, or Arthur's Seat,