The Green River Shales of Wyoming have long been noted for their numerous and beautifully preserved fossil fishes. Fragmentary traces of bird-remains have been met with in the same horizon from time to time since the year 1869, when the first fossil feather reported from North America was obtained by Dr. F. V. Hayden.

The order in which the various mineral constituents of an igneous rock may crystallize out from an igneous magma offers to the petrologist a problem of great difficulty and complexity. It is generally admitted that the order of consolidation is not wholly determined by the order of the fusion-points of the constituents, and with this admission the fusion-points have come to be consistently disregarded, as though they might safely be left out of account. That this is not the case has of late become strongly impressed upon me, especially after a consideration of the important data obtained by Mr. Ralph Cusack, B.A., who, by means of Professor Joly's meldometer, has determined the precise temperature of fusion of most of the rock-forming minerals.

A short time since Mr. G. Trubenbach, Managing Director of the Newlands Diamond Mine, West Griqualand, drew my attention to a notice by Professor Beck of the paper which I read to the Royal Society last June, on the Parent-rock of the Diamond in South Africa, kindly sending me a translation of the original. As Professor Beck's criticisms are founded on such a travesty of my published opinions that I can only suppose his knowledge of our language to be very imperfect, and as the hypothesis which he advances appears to me untenable, I ask permission to reply to the one and point out the improbability of the other.

Last year, while on an excursion to Scotland, I visited the Ardnamurchan peninsula, which, as is well known, consists to a great extent of rocks belonging to the gabbro family. On the road leading from the little village of Kilhoan, opposite the Isle of Mull, on the north coast, a small quarry has been opened for road-metal, which shows an exquisite section of a granophyre dyke intrusive in a dark and almost black fine-grained rock, which the microscopic examination proved to be a gabbro. This is, therefore, a similar occurrence to that of Barnavave, Carlingford, Ireland, which has been admirably described by Professor Sollas, and also that of Strath in the Isle of Skye, of which Mr. Harker has given us a detailed account. As occurrences of this kind seem to be rather rare and, as far as I am aware, hitherto not known from Ardnamurchan, I may be excused for calling your attention to the following short description of these rocks, although there is but little to be added to the results attained by the skilful researches of the above-mentioned authors, and it only shows again that on Ardnamurchan we are to expect very nearly the same geological phenomena as in the adjacent islands, in particular in Skye and Rum.

Gower has a reputation for its caves with their bone-beds, and for its raised beaches, but to the matter of its Glacial Drifts very little attention has been paid.

In addition to the remains of the large Anthracotheriod (Brachyodus africanus) described in the first part of this paper (Geol. Mag., Dec. IV, Vol. VI, 1899, p. 481), the collection of mammalian bones from the Lower Miocene of Moghara also includes portions of the skeleton of a small rhinoceros. Unfortunately this is very poorly represented, there being only an incomplete scapula and an atlas vertebra, and in the absence of any portion of the skull or teeth it is impossible to determine the species to which it may have belonged. As was pointed out in Part I, the age of the deposit is Burdigalien (Lowest Miocene), and it is therefore contemporary with the Sables de I’Orléanais and the fresh-water deposits of Eggenburg. From the latter no rhinoceros remains are recorded, but from the former several species seem to have been obtained. Of these only one, Aceratherium aurelianense, has been described and figured.

My attention has been directed to the following paragraph, which appears in Mr. H. B. Woodward's monograph on the Jurassic Rocks of Britain, vol. iii, p. 31 (1893). It is as follows:—

“Prof. Sollas has suggested that rivers sometimes bear to the sea considerable quantities of undissolved calcareous matter, derived from the formation through which they flow. This is a matter that requires confirmation, for it is known that carbonate of lime is more readily soluble in fresh-water than in sea-water.”

During the seven years 1893–1899, 42 earthquakes have been felt in Great Britain—28 in England and Wales and 14 in Scotland. All of the latter number visited areas which are thinly populated, and it has therefore been impossible to draw the boundaries with the accuracy that is to be desired. In the English earthquakes this difficulty is seldom encountered, and the failures are generally due to the confusion caused by the rather rapid succession of the shocks.

I have from my boyhood been intimately acquainted with Snowdon and its neighbourhood, and for some years past I have been investigating the geology of the district in a systematic manner. In doing this I have paid particular attention to the lake basins, and shall in the following pages give an account of some of my investigations as far as they have gone. I say as far as they have gone, because I hope in the future to make by means of a level more accurate measurements than can be made with a pocket aneroid; and I also hope that next Summer the lakes and tarns will be sounded either by myself or by someone else; for at present we know nothing about the depth of Llyn dur Arddu, next to nothing above that of Glaslyn, and very little about Llydaw, though that little is of great importance.

“Scientific men,” said Professor Thomas H. Huxley, “get an awkward habit—no, I won't call it that, for it is a valuable habit—of believing nothing unless there is evidence for it; and they have a way of looking upon belief which is not based upon evidence, not only as illogical, but as immoral.”

The fossils to which this communication relates were described and the deductions drawn from their mode of occurrence in a paper I submitted to the Geological Society of London in 1896, but as that paper was not printed in extenso (see Q.J.G.S., vol. liii, p. 245), with the Editor's kind permission the gist of it appears as follows.

An important paper on the reputed occurrence of fossil plant-stems in gneiss of Carboniferous age at Guttannen, Switzerland, by Messrs. E. v. Fellenberg & C. Schmidt, for a copy of which I am indebted to the courtesy of the authors, closes, if their view be adopted, a comedy of errors. On this account a brief outline of the story may be of service; for it reduces this supposed relic of Palæozoic forests to a lusus naturæ, and, in any case, once more illustrates the truth of the saying, “we are all fallible mortals.”

Preliminary remarks on the genus.—The interesting observationson the dimorphism of the genus Nummulites, which have been madefrom time to time by special investigators, such as Von Hantken, Munier-Chalmas & Sohlumberger, De la Harpe, Bupert Jones, andVan den Broeok, have resulted in the establishment of couples of so-called species, constituting a species in the zoological sense, in which the smaller form, with a large central chamber, is referred to as form A, whilst form B usually has a larger test and in variably possesses a diminutive central chamber. The two forms are other-wise spoken of as the megalospheric and microspheric forms. In some cases there may be little doubt as to the accuracy of the assignment of the two forms to one species, especially since they may be the only examples present in the rock. In the case ofa stratum containing more than two species, however, there may be no small difficulty in coupling the actual forms which constitute the species, for there is often little in either the internal or external characters to guide one in linking the forms. In our present state of knowledge, therefore, it appears to be most convenient to describe the forms under their specific denominations as already known, at the same time pointing out their relationship to one another. Some good suggestions as to the naming of Nnmmulites and other Foraminifera which exhibit the two modes of growth and shell form have lately been made by Dr. A. Silvestri.

Although the present summary covers the same ground reviewed only a few months ago by the junior bearer of the name which will always be gratefully and prominently remembered in connection with the scientific conquest of Madagascar, the following lines will show that, short as the interval has been, the new additions are not unimportant.

The existence in Anglesey of a series of dykes later than most of the rocks of the island has long been known. Some of the more conspicuous ones were described by Henslow, many more appear on the map of the Geological Survey, and petrological descriptions were given some years ago (Geol. Mag., 1887–88) by Mr. Harker.

The subject of denudation is so important that I propose giving a few instances of denudation and of the transport of material that have actually come under my own observation or that of my friends. Where one sees the same familiar crags and pinnacles year after year, apparently quite unchanged, one may perchance fancy that denudation is at a standstill; but anyone who, in scrambling across the screes that clothe many a steep hillside, finds them moving beneath his feet, or perhaps has clattering about his ears a shower of stones dislodged by some wandering sheep, will at once perceive that it is not so: for it is obvious that if the mere tread of such a small beast as a sheep, shepherd or other pedestrian, can set scree rolling downhill, it must be in a very unstable state, and may be expected to move in a conspicuous manner under more potent forces than the tread of animals. Observation shows that this is the case. Not a year passes without some conspicuous fall of scree or of solid rock, owing chiefly to great downpours of rain. Leaving general statements, I will now give actual instances of the fall of rock or movement of scree that have recently taken place in the Snowdon district.

In recent discussions arising from the renewed attempts to define more closely the boundary between the Jurassio and Cretaceous systems in Russia, Germany, Belgium, and France, and also in North America, constant reference has been made to the English Wealden deposits as affording a standard of comparison. But, meanwhile, doubt has been thrown, by palæontologists who have studied certain portions of the Wealden flora and fauna, on the hitherto accepted classification of these English deposits with the Lower Cretaceous, on the grounds that the fossils showed strong Jurassic affinities. This opinion has been expressed by the late Professor O. C. Marsh in regard to the reptiles, by Dr. A. Smith Woodward in regard to the fish, and by A. C. Seward in regard to the plants. To prevent further confusion it is therefore desirable that certain facts which have been overlooked in this discussion, though for the most part already published, should be restated, since these facts seem sufficient to prove that, at any rate, the greater portion of the English Wealden series must remain as part of the Lower Cretaceous.

In 1877 Dr. Woodward recorded nineteen British species of the genus Conocoryphe, of which seven were doubtful. The following is the list of them:—

This slight, though not uninteresting, earthquake was of intensity 4, and occurred at about 12.30 p.m. I have 20 records from 19 places, and negative records from 2 places.

The able review of my paper on the Geological Age of the Earth which appears in the March number of this Magazine (p. 124), from the pen of the Rev. O. Fisher, raises again questions of such wide interest that some further remarks, referring principally to the criticism of the distinguished writer of the review, and also to criticisms which I have received from others and which are probably in the minds of many who have considered the matter, may not be out of place.