In the March and April Numbers of the Geological Magazine, Mr. J. J. Harris Teall describes some beautiful rocks from the Cheviots, containing a rhombic pyroxene with well-marked pleochroism, and as there seems little doubt that this mineral, which we must consider hypersthene, has been hitherto overlooked in a good many rocks, another note of its occurrence may perhaps possess some interest.

The series of fossil plants from the Tertiary strata of New South Wales and Tasmania, to which these remarks relate, were sent to Mr. R. Etheridge, jun., at the British Museum, for examination partly by Prof. Liversidge, of Sydney University, and by Mr. C. S. Wilkinson, F.G.S., Government Geologist for New South Wales, whilst the remainder already formed a portion of the National Collection.

In the volume of the Palæontographical Society for 1883, I conclude the series of supplements to my work on British fossil Brachiopoda. Additional supplements will, no doubt, be called for every now and then. As our rocks continue to be searched, new forms will turn up, and specimens will be procured that will enable palæontologists to complete the history and illustration of a certain number of those I have been compelled to leave insufficiently made out, described and illustrated.

The Cheviot district is largely composed of those quartzless porphyritic rocks to which the term porphyrite has been applied both by English and Continental petrologists. The Cheviot porphyrites are characterized by a compact felsitic ground-mass, throughout which are scattered numerous crystals of felspar, mostly belonging to triclinic species. The ground-mass varies in colour; the two principal shades being dark purple and red. These porphyrites are evidently more or less altered rocks and sometimes the alteration has been carried so far as to make it almost, if not quite impossible to recognize their original nature by macroscopic examination. Amygdaloidal varieties are not uncommon, and in these agates are frequently found. In addition to the ordinary porphyrites, there occur masses of volcanic ash and breccia, and also a remarkable rock which has been called pitchstone-porphyrite. This is dark almost black in colour, with a well-marked resinous lustre and a specific gravity lying between 2·53 and 2·62. It is porphyritic in texture; the large crystals consisting of a fresh glassy-looking triclinic felspar. Red veins usually traverse the rock in different directions. The boulders lying in the streams are covered with a thin light-coloured crust due to weathering, but at a distance of a quarter of an inch from the surface, or even less, the fresh unaltered rock is always found.

Of the various theories that have been advanced from time to time to account for the origin of jointed structure in rocks, the one that seems to find greatest favour amongst geologists of the present day is that put forth in M. Daubrée’s Etudes Synthétiques de Géologie Expérimental, vol. i. p. 300, et seq., wherein their formation is ascribed to the effects produced by torsion. No one can read the account of M. Daubrée’s experiments without feeling convinced that the deductions he has drawn will enable us to account for the origin of many forms of joints in a manner that leaves little or nothing to be desired. The mere fact that some of the foremost leaders of geological science at the present day hold views on this subject practically identical with his, will, doubtless, be generally regarded as a sufficient reason for accepting M. Daubrée’s theory as one that has supplied a definite and satisfactory answer to the much-vexed question of the origin of joints in general.

It is not every controversialist who has the good fortune to persuade two such distinguished warriors as Baron Richthofen and Dr. Nehring to buckle on their armour and do battle with him; and if there were room for vanity in the shifting panorama of Science, I might at least claim to have stated my case with sufficient point and clearness to make it necessary for more than one elaborate reply. There is no room for vanity however. It matters not who wins, so far as I am concerned, if we only get our difficult problem more sifted and get closer to the truth. If there be no room for vanity, there is less for irony; and I am not surprised that Dr. Nehring should feel hurt if he thinks I have openly or covertly had the indecency to sneer at himself or his work. In referring to Cuvier, it was not to minimize what Dr. Nehring has done, but to do justice to an old philosopher, whose memory I reverence, and whose claims had been overlooked by Baron Richthofen. It was he, I must emphatically repeat, if it needs repetition before such an audience as that reached by the Geological Magazine, who first proved the fauna of the European Loess and its correlated deposits in its broad features to be identical with that found under the Siberian tundras. Cuvier was followed by a great crowd of diligent and close students of this subject, especially in France and America, without naming England.

Brockenhurst fossils were found as long ago as 1858 by Mr. Keeping on Cutwalk Hill, Lyndhurst. He had been lately excavating in the railway cutting near Brockenhurst, at the time that the line was being converted to a double one, and he was anxious to prove the presence of this bed, which just then was attracting much attention at Lyndhurst.

Another series of beds, comprising those which are raised a considerable height above the sea, contain a congeries of mixed shells, often broken, and clearly, as we shall show presently, not in sitû; sometimes the shells are imbedded in sand and sometimes in clay. They contain generally a larger proportion of species, and belong to a more temperate condition of things. The fact that Arctic shells are found in these higher beds is undoubted; but, as I contend, the meaning of this is very different to what is often supposed,—the proportion of purely Arctic shells being by no means large, and under any circumstances the mollusca clearly pointing to a condition of things very different indeed to that which must have existed when the great boulder heaps of Smaland and Finland, which I have travelled across for scores of miles with amazement, were being fashioned,—when our azoic Boulder-clays were being manufactured, and when the mollusca which prevail in high latitudes were driven far to the south, to the Mediterranean and elsewhere, where a few of their descendants are still found in very deep water and sporadically.

Two masses of meteoric iron were discovered in Victoria in 1854, and they were first reported upon by the late W. Haidinger in the Sitzungsberichte A kad. Wiss. in 1861. The smaller block became the property of Mr. Abel, the engineer; the larger one was purchased by Mr. A. Bruce, now of Chislehurst. It appears that Mr. Bruce had seen a piece of iron, which had the appearance of being meteoric iron, in the fireplace of a squatter there, and he asked the man if any more of that kind was to be met with in that neighbourhood. He was conducted to a spot in the adjoining parish of Sherwood, where an irregular spur of iron projected from the surface, and he there and then purchased it with the intention of presenting it to the British Museum. Later on, when they proceeded to dig round it and uncover its sides, they were astonished at its large size. Various sums of money were offered Mr. Bruce for the splendid block, but his one answer to all such offers was, “No; I have bought it for a sovereign; and I am going to give it to the British Museum.” As has been stated, a point only of the iron was above the surface. A photograph was taken on the spot by my late friend, Mr. R. Daintree, the Agent-General for Queensland, after the tertiary sandstone inclosing it had been removed. It is the same sandstone which crops out at Broughton, with basalt from 12–15 feet below, as on the coast at Western Port. Bruce states that the lower bed is Silurian, and that the block of iron penetrated a foot or more into it.

In the September Number of this Magazine, Mr. H. Keeping impugns the accuracy of my father’s view as to the shell-bed at Meadend, which it seems has now disappeared; and says that it was a slipped mass from a bed which, by digging, he found in situ higher up the cliff slope, “close under the gravel with all the Lower Headon Freshwater beds below it”; adding “that he wishes to be distinctly understood to maintain that it is the marine Middle Headon of the Geological Survey, and equivalent to the Middle Headon of Colwell bay, Headon hill, Whitecliff bay, and Brockenhurst in the New Forest.” As I am the only survivor of those who in 1843 worked at this bed, and upon whose discoveries in it my father’s description of it was based, I wish to put on record the facrs at that time, and vindicate my father’s accuracy.

Hitherto I have been in the habit of referring the Gyracanthus spines commonly occurring in the Borough Lee Ironstone to G. formosus or tuberculatus of Agassiz, being disposed to believe in the specific identity of those two forms, as has already been suggested by Messrs. Hancock and Atthey, and hinted at by Agassiz himself. In fact, the salient point of difference between the two is the greater extent of the tuberculation of the ridges in the latter, while in the former it is principally seen on the proximal parts of the ridges, which, as they converge towards the anterior middle line of the spine, become first simply undulated and then smooth. The original figured specimen of G. tuberculatus is from the Coal-measures of Sunderland; that of G. formosus is from the same formation at Dudley; but though Agassiz refers to it as occurring also at Burdiehouse, in Midlothian, and Burntisland in Fifeshire, it seems to me very doubtful if these Calciferous Sandstone specimens are really the same. And certainly the study of a large quantity of additional material from Borough Lee has convinced me that the species of Gyracanthus characteristic of this Ironstone of Carboniferous Limestone age is specifically different from both formosus and tuberculatus.

In concluding an article on “The Climate Controversy” in the Geol. Mag. for September and October, 1876, I observed (p.451) that it had long appeared to me that the “Glacial period proper” was due neither to a change in the earth’s axis, nor to any variation in the eccentricity of the earth’s orbit, nor to any changes in the distribution of land and water, but to a diminution in the heat-emitting power of the sun. In a memoir on the Newer Pliocene period in England, published in the Quarterly Journal of the Geological Society for Nov. 1880, and Nov. 1882, wherein I have endeavoured to trace in detail the succession of events in this country from the commencement of the Red Crag down to the close of the Minor Glaciation, I have reiterated that view, as being the only one that is reconcileable with the succession thus traced; for with the exception of the single interval of warmer climate in which the beds termed by me the “Cyrena fluminalis formation” accumulated, and which was succeeded bythe renewed refrigeration that I have termed the “Minor Glaciation,” and regarded as coincident with the second advance of the Alpine glaciers long ago detected by Continental geologists, I have not been able to discover any indication of those alternations of warm and cold climate, which form an indispensable part of the eccentricity theories of Adhemar, Croll, Murphy and others.

The determination, by means of the chemist's balance, of the specific gravity of rocks and minerals, now more than ever an important element in their classification, is an operation of some difficulty. Various instruments of different kinds have been devised to obtain the same results more easily and expeditiously, and as amongst these there is one I had constructed some time ago and of which I have lately had very favourable reports from practical workers, perhaps an account of it may interest some of the readers of the Geological Magazine.

It is somewhat remarkable that, just as physicists are assuring geologists that the latter will have to quicken their forces, so as to bring the geological history of the globe within the definite limits assigned by the physicists themselves, the geologists reply by adding several thousand feet more rock in various parts of the world to the already thick column of sediment, and many would assure us that these ‘Archœan’ rocks were produced in a manner similar to the fossiliferous rocks, from which they differ in such important particulars.

The gravel mounds and ridges known as Eskers or Kames are, though conspicuous where they do occur from the variability of their outlines, very irregularly distributed in the districts in which they are found. Having been familiar with eskers in Cumberland, I was asked by Mr. H. B. Woodward to visit him at Fakenham this spring for the purpose of seeing whether certain ridges and mounds in the neighbourhood of Glandford and Blakeney were such as are called eskers in the north. And I found that Mr. Whitaker had also met with ridges of doubtful character a little west of Great Massingham. Having just had, accordingly, the advantage of visiting both the localities mentioned, in the company of Messrs. W. Whitaker, H. B. Woodward, and J. H. Blake, this seemed a good opportunity of introducing the subject of eskers to the Norwich Geological Society. The extreme irregularity of their distribution is well illustrated by the fact that not one of the gentlemen named had hitherto met with any esker-like ridges in East Anglia. As eskers are far more numerous and varied in Cumberland than in Norfolk, I will first give some description of those of Cumberland and afterwards refer to the ridges of Norfolk.

The Carboniferous Limestone of the north-west of England was formed in a bay separated from another marine area farther south by a narrow isthmus and promontory never submerged, extending, as Professor Jukes pointed out, in “a band of country running east and west across England from Leicestershire, through Warwickshire, South Staffordshire, North Shropshire into Montgomeryshire,” and to the mountainous district of North Wales.

Within the last few months a good deal has been written upon the question of upheavals and depressions in the crust of the earth both in the Geological Magazine and in “Nature.” By far the majority of these writers have maintained with some show of reason that depressions are the result of the deposition of material of some sort on a part of the earth where it was not previously, in consequence of which the newly loaded part sinks down, just as a weight placed upon an air cushion causes the part on which the weight rests to be depressed. This novel view has been supported by pointing to the fact that numerous instances are met with in which vast thicknesses of rocks have been superimposed one upon another, while throughout their whole depth traces of shallow or comparatively shallow water are found, it being inferred that the sedimentary deposit being the cause of the depression, the bottom sinks exactly in proportion to the amount of the deposit. The Carboniferous system has been advanced as a conspicuous instance of this state of matters; the same holds true of the lower Old Red Sandstone, which appears to have been deposited in lakes.

We may pass next to the Sam Meylltern district, to examine the patch which Dr. Hicks on his sketch-map [Q.J.G.S. vol. xxxv. p. 297] has indicated as Dimetian with a strip of Arvonian along the north side. We read [l.c. p. 300], “Eastward (sic) of this, and as we approach the so-called altered Cambrian, rocks of a more felsitic character come in abruptly, and it is probable that these are of Arvonian age.” At the north end of the patch, by the Cromlech and Amwlch Lodge, the rock is however of the type which Dr. Hicks has termed Dimetian, and as it varies much in character at different parts of its course, I think we must ask for further proof that there is a second bed of rock of different age, in this area.

No fact in Physical Geology is more frequently recorded than a simultaneous occurrence of subsidence of the earth’s crust where deposition of sedimentary strata has been in progress. Reference is often made to the fact that the basement beds of different sedimentary formations were deposited in shallow water, and to the indications presented by subsequent deposits that they were accumulated in a sea of moderate depth. On them immense accumulations may have been deposited in successive strata, amounting even to miles in thickness; showing that with the deposition there has been a corresponding depression of the original surface. Though these phenomena are so inseparable in their occurrence and so well known, English geologists, until the last few months, have made little, it may even be said no endeavour, to determine whether they should be associated as cause and effect. This has not been the case with American geologists.

With the increase of population and the simultaneous pollution of rivers in this country, the question of water-supply for the purposes of human life becomes every year a more serious one. Among the many schemes which have been advanced for the supply of London with water, it has been proposed by a high authority to bring the Bagshot Sands of the London Basin under requisition. These strata, covering, as they do, a considerable area at no great distance from the metropolis, and being for the most part of a porous character, would appear to form a convenient reservoir of water, since they contain stored up within them a large portion of the rain-water which falls on portions of Berkshire, Surrey, and Hants. The water obtained from these sands, either from surfacesprings or deep wells, is free from calcareous hardness, but is highly charged with salts certain of iron, which, by oxidation on exposure to the air, yield an ochreous red precipitate, the nature of which seems generally to be but imperfectly understood. The inconvenience, however, which results, in the turbidity of the water after no great exposure to the air, and the rapid corrosion of iron pipes in which it is conveyed, are facts with which all inhabitants of the Bagshot country are only too familiar. The fact that this property of water drawn from the Bagshot Sands varies greatly according to the portions of those strata which furnish it, does not however appear to be so generally known. Recent difficulties in connection with the water-supply of our own particular district have forced the matter upon my attention; and as I have been able to arrive at some pretty definite results from the investigations in which I have been engaged for several months past, it has occurred to me that, as forming a subsidiary subject to geological science, they may be of interest to readers of the Geological Magazine.