The relation of the Torridon Sandstone to the Moine Gneiss or ‘Eastern Schists’ is one of the primary questions in thegeology of the Scottish Highlands. These two widespread series ofrocks occur on opposite sides of the great overthrusts in North-Western Scotland; and another remarkable feature of their distributionis that though the Torridon Sandstone often rests directly upon theLewisian Gneiss, it never occurs on the Moine Gneiss. The view hastherefore been suggested that the Moine rocks are the easternmetamorphosed continuation of the Torridonian. Some altered Torridon Sandstones certainly resemble the rocks of the Moine Series.Dr. Home, in his address to the British Association in 1901, quotedthe authority of Dr. Teall and Dr. Peach for the resemblance ofaltered Torridon Sandstone to the Moine; and he again remarked thisresemblance in the memoir on the North-West Highlands. The lateW. Gunn went further, and in the same work claimed (p. 612) that “east of Dundonnell good evidence can be adduced that alteredTorridon Sandstone has entered largely into the composition of the Eastern schists”. The recent memoir on the Fannich Mountains represents some of the flaggy granulites of that district as due “to the crushing of Torridonn grit”.

The present paper is the outcome of a number of visits which, during a prolonged professional residence in Italy, I paid to Piémont, Lombardy, and the Italian lakes, and in the course of which I became familiar with the glacial phenomena and the lake basins along the southern base of the Alps.

The intrusive rocks of Marston Jabet and Chilvers Coton, though probably of quite minor importance, have been rendered noteworthy by the variety of opinions held regarding their true position in a scheme of rock classification. This is especially the case as regards the rock quarried at Marston Jabet. Thus Allport comments upon certain remarkable features distinguishing this rock, which, however, seems to be covered by his general statement that the intrusive rocks of the Warwickshire Coalfield are for the most part ordinary diorites. Rutley concurs in the opinion expressed by Allport. Watts calls attention to the lamprophyric aspect of the rock, which he terms a camptonite; and with this description Harker agrees. Hatch admits the lamprophyric features and incidentally refers to the lack of recorded analyses.

All the phenomena hitherto noticed have been worked out for the case of rocks altered in situ, but they also take place in the products of transport resulting from the demolition of laterites in situ.

The range of the Apuan Alps, commonly called the Carrara Mountains, is an offshoot of the Apennines, trending N.N.W. to S.S.E., parallel to the Mediterranean littoral, from which it rises within a distance of barely four miles to a maximum height of 6,000 feet above sea-level. Exclusive of the outer belt of the more recent strata, the Triassic formation, within which the saccharoidal marble beds are situated, covers about 25 by 13 kilometres or about 130 square miles, of which the marble zone proper represents 64 square miles or about half. The range is bounded on the north by the Aullela valley in the Lunigiana district; on the east by the Serchio valley in the Garfagnana district; and on the south by the Serchio valley in the Province of Lucca. The marble district, whose western part faces the Mediterranean, comprises the three divisions of Carrara, Massa, and the Versilia in the corresponding parallel valleys of the Carrione, Frigido, and Serravezza Rivers. The Versilia division, which forms part of the Province of Lucca, is composed of the Seravezza, Stazzema, and Arni subdivisions, of which the last-named lies on the eastern watershed of the Apuan range. The Versilia division also includes Pietrasanta, Camajore, Massarosa, and the wellknown watering-place of Viareggio, near the last-named of which are situated extensive subaqueous deposits of a peculiarly coarse-grained, sharp macigno sand. These deposits, formed as a delta in a lacustrine expanse by the River Serchio, constitute an important and indispensable adjunct of the marble industry as grinding material for the numerous marble saw-mills in the three parallel valleys already referred to.

There have now been described all the known members of the Edrioasteridae and the very similar genus Stegarioblastus, as well as a genus apparently connected with the Agelacrinidae but presenting some remarkable features, namely Pyrgoeystis. It is proposed in this and the following Study to deal particularly with the Edrioasterid organization, first considering what the known facts of skeletal structure imply as to the general anatomy and mode of life, secondly comparing the structure with that of other echinoderms, especially the Asteroidea. Although it may be necessary to refer to various facts that fall to be dealt with in future Studies, still the present seems a convenient opportunity for this general discussion, because of the recent publication by Mr. W. K. Spencer of the introduction to “A Monograph of the British Palaeozoic Asterozoa” (Feb., 1914, Palæontogr. Soc. vol. for 1913), by Dr. J. F. Gemmill of his highly important memoirs on the starfishes Solaster endeca (1911, Proc. R. Phys. Soc. Edinburgh, vol. 18, pp. 174-91 ; and Feb., 1912, Trans. Zool. Soc. London, vol. 20, pp. 1-71, pis. i-v) and Asterias rubens (Oct., 1914, Phil. Trans., ser. B., vol. 205, pp. 213-94, pis. xviii-xxiv, and March, 1915, Proc. Zool. Soc. London, pp. 1-19, pis. i-iii), and by Dr. A. F. Foerste of some suggestive “ Notes on Agelacrinidæ” (Sept., 1914, Bull. Sci. Lab. Denison Univ., vol. 17, pp. 399-486, pis. i-vi).

In this zone the phenomenon of départ or leaching is carried to a finish, and though of little significance in the case of the gibbsitic laterites of the diabases, gabbros, and syenites, since these from the beginning of alteration in the zone of leaching have been deprived of the greater part of the elements to be removed, yet in the case of the mica-schists it is of great importance. But in every case there is an accentuation of a phenomenon already evident in the preceding zone, namely the emigration of iron towards the surface, where it becomes concentrated. At the same time concretionary phenomena, often resulting in the separation of the hydrates of iron and aluminium one from the other, become increasingly important and reach their maximum development quite close to the surface, where they lead to the formation of a resistant crust (cuirasse), in which hydroxide of iron acts as cement; this hydroxide may even become sufficiently abundant to constitute an ore of iron, particularly in the case of certain diabases, and above all of peridotites.

In the preceding paper I dealt with the five principal and zonal sub-Alpine lake basins in relation to their age and origin, while the object of the present one is to group and consider the more prominent of the smaller Swiss lakes which I have had repeatedly occasion to visit and examine. Omitting the high altitude lakes, such as the Merjelen and the Engadine Lakes, which I described in previous papers, as also the hundreds of lakelets disseminated throughout Switzerland, I shall confine myself to those lake basins from whose glacial or hydrographic features definite conclusions may be drawn. The illustrations (Sheets Nos. 1–4, Figs. I–X), having to cover the large area of Central and Northern Switzerland, are necessarily drawn to a small scale, but all particulars may be gleaned from the Swiss 1 : 25,000 contour map, to which the metric altitudes and dimensions in this paper correspond.

Another type, which is found in both quarries and which under the microscope has the aspect of a monchiquite or limburgite,. probably represents the actual marginal rock of the intrusion. It consists of small microphenocrysts of augite and olivine in a dark matrix, which can be resolved into granular augite and magnetite in a nearly isotropic base. The latter, which sometimes contains felspar microlites, seems to be mainly analcite with some nephelite, as it can be readily gelatinized and stained, while the refractive index is very low. The felspar microlites are small and sometimes have a rough trachytic structure resembling that of the mugearites. Following Harker's suggestion that augite-olivine rocks with an isotropic base should be classed as limburgites when the base is glass and as monchiquites when it is analcite, this rock can be included in the latter, group. The parts which are richer in felspar may be termed analcite-basalts.

In two papers read before the Geological Society in 1904 I showed that the five principal lake basins of sub-Alpine Switzerland lie in a zone which is parallel to the Alps, and that this zone lies almost entirely in the Molasse formation. The conclusions which I drew from these facts as to the age and origin of these basins having, since then, been confirmed by further evidence, it will not be without interest to return to the subject.

Although the calcium oxide and magnesia of sedimentary limestone and dolomite must all be derived from pre-existing igneous rocks, it is not so easy to trace the origin of the necessary carbon dioxide. The solidified igneous rocks contain mere traces of free carbon dioxide and of calcite. During their weathering carbon dioxide is taken up from the atmosphere, replacing the silica of calcium silicate and magnesium silicate minerals, and forming the carbonates. Now, however, the quantity of carbon dioxide retained in the atmosphere is exceedingly small. It is difficult to credit, for instance that a layer of coal, 1½ millimetres thick, covering the surface of the globe, on being burnt would yield as much carbon dioxide as the entire atmosphere now contains. A similar layer of limestone containing an equivalent amount of carbon dioxide would have a thickness of 5 millimetres. This is out of all proportion compared with the mighty beds of limestone and dolomite now forming part of the earth's crust. Nor would the carbon dioxide of the sea avail anything. It exceeds in quantity that of the air, but is still at the most equivalent to 7 centimetres of limestone covering the earth's surface. Now the existence of animal life throughout the sedimentary era implies that from the earliest times, the composition of the earth's atmosphere cannot have differed very materially from the present one.

While no doubts have existed among geologists that the rocks of this district are of Permo-Triassic age, that they are surrounded by older formations of the Carboniferous Series, and capped by a small Lias outlier, unanimity as to the relations of the local Perrao-Triassic rocks to each other has never yet prevailed. Hence when the Geological Survey Memoir, by the present writer, on this district was published in 1899, Sir Archibald Geikie stated in the preface tliatthe delay in its appearance was due to the hope that additional deep borings might have settled certain questions as to the relations to each other of the rocks above the St. Bees Sandstone, etc. On this account, my own views (as those of the worker on the Geological Survey in this district) were allowed to be given by me in a paper read at the Geological Society in 1881, on “The Permian, Triassic, and Liassic Rocks of the Carlisle Basin” (Q.J.G.S., vol. xxxvii, May, 1881).

This paper gives the results of investigations made during the early part of the present year with the object of elucidating the relation of the Coal-measures to the Lower Carboniferous rocks in the Clapton and Clevedon districts of Somersetshire.

An important factor in the formation of this drainage area as above outlined is the movement of the rocks after they had been reduced to a surface comparable with a peneplain. These movements are now reviewed to see if any assumptions have been made which are probably incorrect from stratigraphical evidence.

In the very interesting paper by Mr. Arthur Holmes on “Rradio-activity and the Earth's Thermal History”, in the Geological Magazine for February and March, it is assumed that in Archæan times there was “a widespread molten condition at no very great depth” below the earth's surface, and in the final conclusions the statement is made that “geological and other evidence points favourably to the traditional view that the earth's crust was initially in a molten state”. The results of recent work on the Archæan of Canada do not bear out this traditional view of the conditions of the earth's earliest known geological period, and it may not be amiss to suggest some points that decidedly conflict with it.

A short while ago I received from Professor A. Lacroix a copy of a recently published memoir on the laterites of French Guinea, accompanied by the request that I should, if possible, give an account of this work in the Geological Magazine, “puisque c'est là qu'ont paru les articles les plus importants sur cette question.” I have undertaken this task with the greater pleasure because Professor Lacroix was so good as to show me, when I was passing through Paris recently, both his hand-specimens and his microscopic preparations of these rocks, and because the memoir in question seems to me to be one of the most important and thorough pieces of work on laterite published since Max Bauer's account of the laterite of the Seychelles. Although Professor Lacroix' memoir deals professedly with French Guinea only, yet it is probable that many of the conclusions will be found to apply to other regions, and on this account, and because the series in which the memoir appears will probably not be readily accessible to all, I have thought it desirable to expound it at some length.

On approaching the problem of the origin of laterite, the first thought that strikes one is that there is an apparently fundamental difference between the modes of decomposition of aluminous silicates in temperate and in tropical regions. For in temperate regions the end product is a clay, in which the original aluminous silicates are represented by hydrated aluminium silicates approximating in composition to kaolinite, whilst in the tropics the end product is laterite, in which the original aluminous silicate is represented by a mixture of hydrated aluminium oxides. The two processes may be expressed by the following chemical equations:—

Perhaps one of the most unexpected facts concerning the geology of the Polar regions is the almost entire absence of pre-Quaternaryrocks composed of glacial detritus, and the presence there mainly ofsediments containing floras and faunas indicating warm climaticconditions. This is true of the rocks composing the AntarcticContinent as well as of the land masses in the neighbourhood of theArctic Sea. Indeed, it is not until rocks of late Tertiary or Quaternarytimes are reached that we get any signs of continuous frigid conditionsat the Poles.