A Controversy apperas to be carried on between geologists as to the causes of the excavation of valleys, and the degree in which marine denudation on the one hand, or the eroding power of rain and rivers on the other, have been concerned in the process. To this controversy Mr. D. Mackintosh has contributed two papers, in recent numbers of this Magazine. I am desirous of recalling to the recollection of its readers certain facts which demonstrate, beyond the possibility of doubt, how vast is the error of those writers who, like Mr. Mackintosh, speak of “the impotence of rain as a denuding agent.”

The Coast-line which I am about to describe extends from the Vale of Clwyd, in Flintshire, to the Great Orme's-head Mountain at the northern end of the Menai Straits.

No complete list of the Stonesfield Fossils has been drawn up since 1855, when some remarks of mine on the Geology of the vicinity of Oxford appeared in the first series of Oxford Essays. During the last eleven years we have received from that rich locality many additional specimens, but not many species new to the University Museum. One has lately reached my hands which I hope will be of interest to the readers of the Geological Magazine, as adding something to the knowledge of a prevalent group of water-side insects, which had left witnesses of its existence through a very large range of Geological Time, viz. the Neuroptera, and specially the Libellulidœ.

The following letter has been forwarded to me with a request ot make a few remarks upon the flint-cores mentioned by General Twemlow:—

The special proofs of metamorphism which it is the object of this paper to point out, are rather of a geological than chemical nature. They consist, in short, of such evidence as may be readily gathered in the field, and although, to render them complete, they ought perhaps, to be followed up by analyses of the rocks, yet it is believed that the phenomena to be described tell a plain enough story.

While referring the present “form of the ground,” in a large degree, to the several agencies of atmospheric and marine denudation, do not let us ignore the, at least, equally efficacious action of subterranean force. This Professor Jukes appears to me to do, to an extent likely to mislead ordinary readers, naturally influenced by his high authority, in the communication from him published in your last number (Vol. III. p. 232). He there speaks of “the action of internal forces,” as “having no direct effect on the external features of the ground.” In a subsequent sentence, indeed, he makes exception, in a parenthesis, of “volcanic cones and craters,” but seemsto consider these exceptional cases as of trifling moment, and to deny altogether the influence of other internal forces in producing superficial elevations or depressions.

I have lately had an opportunity of taking a hasty examination of the part of Yorkshire lying between Bramham Moor and Fountains Abbey for the especial purpose of examining the “Lower New Red Sandstone,” so elaborately described by Professor Sedgwick many years ago, and lately alluded to by Professor John Phillips, in a paper read before the Geological Society.

As I have prepared descriptions of nearly all the fossils of Victoria collected by the Geological Survey under Mr. Selwyn for some years, I have been urged to make a preliminary publication in the Geological Magazine of some ofthe remarkable forms, and I now forward my descriptive note of the two Tertiary Trigoniœ, on account of Mr. Jenkins' paper in the May number of this Journal, in which one of them is referred to the recent T. Lamarckii. I feel assured that if Mr. Jenkins will look at the edge along the ribs, towards the beak of a recent specimen of T. Lamarckii and my T. acuticostata from the Tertiary beds, he will at once appreciate the distinctive form of the ribs which I point out and figure in the annexed woodcut.

In a paper that appeared in the “Geologist” for May, 1863, the author, Professor King, has noticed the remarkable escarpments that occur in the Burren Hills, on the south side of the Bay of Galway. He is of opinion that they have been formed by sea action during the slow upheaval of the British area after its submergence during what he calls the “subaqueous“ or “middle division“ of the Glacial period, and that “every escarpment indicates a stoppage in the upheaval.“ These escarpments, or ancient seamargins are not confined to the Burren Hills, as I have observed them in various other localities, but never so continuous, nor so well developed. In this paper it is proposed calling attention to those in counties Clare and Galway. I shall first notice the conspicuous escarpments in the Burren Hills, but before doing so I may be allowed to refer to similar phenomena in course of formation at the present day.

In the Geological Magazine, 1865, Vol. II., p. 308, reference is made to the recent discoveries of Whitney as to the occurrence of Gold in rocks of California even of an age as recent as Cretaceous. These discoveries fully confirm my previous results in South America, yet the examination of a series of specimens recently sent me from California makes me communicate these few observations upon the relations of the gold-bearing rocks in question and some remarks on the views which I have expressed with reference to the geological periods at which gold has made its appearance in the crust of our globe.

Geological Structure of Malta.—The Island of Malta is entirely composed of Tertiary aqueous rocks, which lie in a nearly horizontal position, but which, being traversed by several faults, are found at very different levels. This horizontal position of the strata is interesting, as it is seldom seen in small islands situated so far from the main land; and it is probably to be accounted for by supposing that any unequal pressures which might have occurred during the upheavels of the Island, expended themselves in the production of faults, instead of inclinations and contortions of the strata.

This article will be devoted to the consideration of the indications of marine and fluviatile denudation furnished by the cliffs, gorges, valleys, and other phenomena, of some parts of Central and North Wales. With the view of collecting facts, the author, during April and May of the present year, resided successively at Builth, Rhayader, Aberystwyth, Dolgelley, Newtown, and Llangollen, so as to have opportunities for repeated observations; and the following notes refer chiefly to the neighbourhood of these towns and the intervening districts.

It was my intention to have devoted this paper to the Coniferous Fruits found in Strata of Secondary age in Britain, reserving for future examination, those belonging to the later periods, but in the progress of my investigations I have found that, two remarkable cones, which have hitherto been considered as belonging to the Greensand, are certainly Tertiaryfossils; and having placed them on the plates which illustrate this paper, I shall include them in my descriptions.

I Have been favoured by the Rev. Peter B. Brodie, M.A., F.G.S., with part of the lower jaw, including eight back teeth (Pl. X., Fig. 1, natural size), of a small mammal, nearly allied to Spalacotherium tricuspidens, Ow., and from the same formation and locality, viz., the Marly bed Upper Oolite, Purbeck, Dorsetshire.

The pages of the Geological Magazine have lately contained some interesting articles on denudation. I wish to add some further remarks on the subject, which I think will, if duly considered, add important elements to the discussion of that problem.

Although volcanic rocks of Permian age have long been known to occur abundantly in Germany, their existence in Britain does not appear to have been recognized up to the present time. Trapdykes, indeed, are far from rare among our Permian strata; there occur likewise many igneous masses penetrating the higher portions of the Carboniferous formation; but the former are evidently later than the Permian period, while the latter may be anterior to it. The history of volcanic action in the British isles, so far as I am aware, embraces as yet no clear evidence of Permian volcanos. In the present communication I propose to fill up this gap by showing that during the formation of the Permian sandstones a series of small but active volcanos was scattered over the south-west of Scotland.

While we have in the deposits described no signs of any line of drainage conterminous with the valley through which the Thames now finds its way from London to the sea, until after a series of diverse conditions, and until a most recent date,—that of the Marsh clay, we shall find, in the physical structure of the valley, evidence corroborative of that afforded by the deposits; and showing that the present valley of the Thames is a creation subsequent to all the deposits which it contains that are older than the Marsh clay.

I regret that this short but important communication was too late for insertion in the December number of the Geological Magazine, as it was intended to announce the discovery of no less than four, if not five, new Genera of Amphibian Labyrinthodont Reptiles from the true Coal-beds of Jarrow Colliery, Kilkenny, Ireland.

In connection with the discussion on the origin of hills and valleys, which has recently occupied the pages of the Geological Magazine, I would submit a few observations on some phenomena, in evidence of the great power of subaërial denudation, which seem scarcely to have been noticed with the prominence they deserve. I assume that the joint action of sea and river denudation is un-questioned, and that the main point under discussion is relative to which of these processes determined the final contour of the land. What I wish particularly to notice is that the forma of the whole land surface with some trifling exceptions (as lake basins, which appear to admit of special explanation) is merely a modification of the same principle of contour as the true river valley, exhibiting a system of watersheds by which almost everypart of the land is connected with the sea by adjacent land on a graduated series of levels lower than itself.