The beautiful fossil Star-fish, which forms the subject of this paper, and is represented of the natural size upon the accompanying Plate VIII., is from the cabinet of Mr. Henry Johnson, of Dudley, the Honorary Secretary of the South Staffordshire and East Worcestershire Institute of Mining Engineers. It was obtained some years since in the shale between the Wenlock and Aymestry Limestones (probably Lower Ludlow shale), at Sedgley, near Dudley.

The igneous theory of the earth's crust, which supposes it to have been at one time a fused mass, and to still retain in its interior a great degree of heat, is now generally admitted. In order to explain the origin of eruptive rocks, the phenomena of volcanos, and the movements of the earth's crust, all of which are conceived by geologists to depend upon the internal heat of the earth, three principal hypotheses have been forward. Of these the first supposes that in the cooling of the globe a solid crust of no great thickness was formed, which rests upon the still uncongealed nucleus. The second hypothesis, maintained by Hopkins and by Poulett Scope, supposes solidification to have commenced at the centre of the liquid globe, and to have advanced towards the circumference. Before the last portions became solidified, there was produced, it is conceived, a condition of imperfect liquidity, preventing the sinking of the cooled and heavier particles, and giving rise to the superficial crust, from which solidification would proceed downwards. There would thus be enclosed, between the inner and outer solid parts, a portion of uncongealed matter, which, according to Hopkins, may be supposed still to retain its liquid condition, and to be the seat of volcanic action, whether existing in isolated reservoirs or subterranean lakes; or whether, as suggested by Scrope, forming a continous sheet surrounding the solid nucleeus, whose existence is thus conciliated with the evident facts of a flexible crust, and of liquid ignited matters beneath.

During my recent stay at Geneva the eminent geologists MM. F.J. Pictet and P. de Loriol showed me a very considerable number of fossils, which they had collected from the middle and lower portions of the Cretaceous system of Switzerland and Savoy, and carefully explained the position of the beds from which they had been obtained. M. Pictet subsequently, at my request, recorded in manuscript his most recent views in connection with this important topic, of which I will shortly reproduce a translation for the benefit of the readers of the Geological Magazine. He has, however, restricted his table and explanations to the middle and lower portions of the Cretaceous system, because the regions which surround Geneva do not exhibit any representatives or evidence in connection with the upper stages. M. Pictet has also explained his views with reference to the rock which, at the Porte-de-France, contains the Terebratula janitor, and of the Carpathian or Stramberg limestone, which has been placed by M. Hébert at the base of the Cretaceous system, but which others have referred to the Jurassic epoch. The correct determination of the true age of these rocks is a subject of very great importance, since they contain a rich assemblage of species bearing a particular and well-marked stamp, as may be seen by a glance at Professor Suess's admirable monograph, “Die Brachiopoden der Stramberger Schichten,” as well as at those by Zettel, etc., on other classes.

Previous to writing “Suggestions on Denudation,” I had not seen Mr. Darwin's paper “On the Formation of Soil;” since then, having read this essay, it appears to me that instead of Darwin proving “the disappearance of stones, etc., needs no growth of soil,” he advocates in a great measure the statement put forward in “Suggestions on Denudation.” For Darwin clearly proves that any foreign sustance placed on grass land will be gradually covered up by a growth of soil over it. This soil, however, he seems to believe to be entirely due to the labour of earth-worms, who excavate in the ground under the foreign sustance and deposit over it. From this it would appear that this eminent observer considers that the total thickness of the soil is not increased upwards by mould formed from vegetable decay, but that all is taken from below the foreign sustance and placed above it, thereby adding to the thickness of the upper stratum of the mould and diminishing the thickness of the portion below the foreign substance. This, within certain limits, may be correct; but can anyone asset that the decay of the yearly growth of vegetable matter is nil, and that it cannot possibly and its mite, no matter how small, to the thickness of the soil? If the above is the case, how can we account for the growth of peat bogs in Ireland and other countries? On the site of all peat bogs (or the bogs in the low flat country) there originally was vegetable soil, in which trees and lesser plants grew;—on this, by the decay of the vegetable matter, a spongy soil was formed that retarded the drainage, and was well fitted for the growth of such mosses as the Sphagnum, which began to luxuriate.

The importance of experiments and investigations such as those recorded by the Rev. J. D. La Touche, in the Geological Magazine for April, can hardly be over-estimated from a geological point of view, and, if carried on in numerous districts and for a sufficient length of time, would furnish data with which, and a basis from which, future calculations as to the rate of denudation at present going on over the land surface of the globe might be esti- mated. For it cannot be denied that at present there is a laxness in the method of computation as regards the rate and amount of degradation both for past and present epochs which ill accords with the ultimate end and aim of all scientific pursuits, viz., truth. Each one taking a rate which seems most to confirm his own particular tenets, as, for instance, the different rates at which the river Niagara has out its way back from Queenstown Heights to the present situa- tion of the Tails. It has been taken as three feet, one foot, six inches, and one inch per annum, by different computators. Now I do not say that investigations on the river action of the period in which we live will clear up all such anomalies, because these obser- vations will be of more service in estimating the future rate of the wearing down of the materials composing the land than that of the past, as there would always be the difficulty of ascertaining with precision the volume and velocity of the rivers, and the different elevations at which the land was situated at the particular era under consideration; still it would be a fulcrum on which we might rest the lever of analogy, and raise many questions at present resting in obscurity and doubt into light and certainty.

The little village of Crossby-Garrett, near Brough, appears to occupy the site of a Post-glacial lake. Lower Carboniferous strata compose the fell to the south, the lowest beds being yellow earthy limestones. Below this, in all the gorges, are deep red shales of the uppermost Old Red. and on the summits of some of the hills to the south are outliers of the New Red; the Drift lies in patches and contains mud, sandstone, and numerous blocks of Shap granite. The gullies coming down from Crossby fell converge at the gate of the village, and show excavation in Boulder drift. The bed of the torrent is dry during the greater part of the year, it receives only the surface water, which, as it falls swiftly down the valley through the Drift, makes rough work of its sides every freshet. Underneath the church hill, at the lower end of the village, the remains are visible of the dam which once enlaked the little valley. It has been clean cut through by the bursting of the Lake, and the banks of the exca- vation, and bottom of the old lake are now occupied by cottages and gardens. Another small lake existed near the village, in fields still called the tarn-fields, but whilst the former must have been drained, probably in pre-historic times (judging from the subsequent work of the torrent), the latter has disappeared by artificial drainage into the Smardale beck within a century.