agitating the minds of the present generation of biologists, and it seemed to me that a sketch of the theory in question, and its bearings upon the problem of the factors of organic evolution might be of considerable interest to those of your readers who have not the time or inclination for a thorough study of the question. I hope now to be able to carry out my original scheme and contribute the papers alluded to..

My immediate object, however, in the present instance, is to enter a strong protest against the very unfair and misleading way in which the question has been now attacked in your pages (SCIENCE-GOSSIP for February, pp. 25-30).

Mrs. Alice Bodington sets out by deploring that Mr. Wallace has been "hardly, if at all, influenced by the discoveries of the last quarter of a century," and concludes by stigmatising the Neo-Darwinians as an unprogressive school which arrogates to itself the right of claiming to be his (Darwin's) special disciples." Between these two startling statements we have a great deal of talk about "inherent" and "internal" forces, initiating variation" or rendering it possible,” and about many other equally curious notions of the phenomena of heredity and variation. There is hardly a line of argument in the article, only a series of vague denunciations of the supposed one-sided views of the Neo-Darwinians, founded on a series of the most astounding misconceptions of what those views are, and of the real questions at issue.

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It hardly appears worth while to go through the paper pointing out these misconceptions in detail, but it may be as well to notice a few. Mrs. Bodington'says we are gravely asked to believe that all these modifications are the result of a series of accidents occurring generation after generation with results more and more marked, yet all uninherited and accidental!" What does this mean? Nobody in his senses ever asked anyone to believe such an astounding travesty of the theory of natural selection.

Surely, it is at this period of time unnecessary to point out that the word "accidental " applied to congenital variations, merely means that the original occurrence of any particular variation has no reference to the purpose which it serves, and which enables it to be fixed by natural selection. Again the inheritance of such variations is an experimentally established fact-a fact, moreover, on which the whole theory of natural selection rests. What we do deny is the inheritance of a character acquired during the lifetime of the individual. Mrs. Bodington has entirely lost sight of the distinction between these two kinds of characters, which is the whole point of our position, with the absurd result that she talks about being asked to believe that "accidental" (congenital) variations are "uninherited," and about " prepossessions against heredity!"

Again, no one in his senses stated the "Law of the action of the environment upon irritable Protoplasm" to be "non-existent." All that is contended is that the effects of such action are not, among the metazoa, transmitted, as such, to the offspring.

Professor Weismann does not consider that he has proved his theory of heredity and variation at all, in his laboratory or elsewhere, nor did the wildest enthusiast ever contend that laboratory work will 'explain everything." That his theory is " contradicted by the evidence of palæontologists' " is impossible, since it is impossible that palæontological evidence can touch such a theory.

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Mrs. Bodington apparently refuses to believe in "a predisposition to point on the part of a germ," yet it is sufficiently obvious that such a predisposition' must exist in the germ, however it has got there, or else how is this character transmitted from parent to offspring?

Mrs. Bodington says of Professor Weismann's statement that "the inheritance of acquired characters has never been proved either by means of direct observation, or by experiment," that "such an assertion takes one's breath away ; " but she carefully refrains from stating a single instance in which such inheritance has been proved. It is no answer to inform us that Darwin believed in such inheritance, that his belief increased somewhat in later years, that Mr. Herbert Spencer believes this form of inheritance to have been still more important. We know these things, but we are still waiting for proof of such inheritance-proof such as we have in abundance as to the inheritance of congenital variations.

As to the right of those who deny that we can accept the inheritance of acquired characters as a factor in evolution to claim that they are advocating pure Darwinism, we can only say that they are laying still more stress on the factor which Darwin first pointed out, which he always believed to be far the most important one, and which is for ever connected with his name. A. G. TANSLEY.

every variety of wader. The lakes and rivers, teeming as they are with fish, invite to their rippling surface crowds of hungry water-birds. It would be safe to assert that we have quite a hundred and thirty different kinds of birds, which stay with or visit us during the course of the year.

The golden eagle can sometimes be seen, either hovering over some doomed hare, or circling round and round on the look out for a victim, to satisfy its appetite. A pair of these birds build every year on a

tree

near Invermoriston; but they are strictly preserved, or their eggs would soon fall into the hands of some naturalist. But these birds can only be seen among the hills, as they seldom venture near the more cultivated ground in the valleys. The bold peregrine is the largest of our falcons. I once saw a very interesting battle between a couple of these warriors and a golden eagle. It lasted for upwards of an hour, but, unfortunately, I was not able to see the end of the battle, as the combatants went over the neighbouring mountains. There are three nesting places of this bird known-one of them not more than a mile from the village of Fort Augustus. A pair of merlins used to live here, but they have recently been shot by some keeper. Sparrow-hawks and kestrels are also seen-the latter in great abundance, for there are no less than ten nests in the neighbourhood of the village. The pretty osprey, or fishing hawk, is among our many visitors in the spring. It formerly laid its eggs along the side of Loch Ness, on a tree jutting over a precipice, but even in this secure position its eggs were taken, so it was obliged to shift its quarters, and it is not known for certain where it builds at present.

Finches, buntings and other species of little birds are fairly numerous, chaffinches and yellow-hammers being about the commonest. The pretty little siskin has been shot here more than once, but it is considered a very rare bird. A great grey shrike was shot by one of the boys of our college in the act of eating a redpole. The nest and eggs of a red-backed shrike were found some years ago. We have very few birds belonging to the swallow family. The sand martin, certainly, cannot be called rare, but both the swallow and the house martin are very scarce. Swifts are also decidedly rare. House martins and swallows used frequently to be met with, building in great numbers under the eaves of the college tower, but of late they have quite deserted us. I have only seen one nightjar, and have not heard of the nest or eggs having been discovered. Crossbills come over in large flocks, during the month of July, and a few pairs are often seen about April or May, but they are usually shot down and not given a chance to breed. Thrushes, ring-ousels, dippers, wheatears, and others of this family are in great numbers during the spring and summer. The plantations are inhabited by flocks of tits and golden-crested wrens.

The Corvida family are exceedingly numerous,

especially the little jackdaw, which builds in the rabbit holes on a precipitous cliff, surmounted by an ancient vitrified fort. Hooded crows are by no means rare they live along the birch-covered hills, and a keeper once told me that he destroyed about forty nests belonging to this bird, during one season, in his own district. Rooks and crows are not so numerous as in other places. The bold raven, however, is a resident in the district. There are three nesting places, but they are all among the hills, as this bird is very shy and likes to make its home as far as possible from the haunts of men.

There are three different kinds of grouse here, namely the red and black grouse and the ptarmigan. The two first live on the extensive moors on the mountain sides, while the last can only be found on the tops of the highest hills. Corriearrick, on the road to Kingussie, about ten miles off, is the best place to see them, and their eggs have been discovered there. They can only be visited in the summer, as the place is inaccessible in winter, on account of the snow, so the birds are not seen in the best of their plumage.

The only kind of pigeon we possess is the wood pigeon, or ring-dove. These are found in countless numbers among the wooded glens, and thence they come in flocks to the cornfields, from which each carries away its cropful of corn.

The waders are most numerous in the seasons of spring and summer. During the month of March, our swamps are filled with plovers, snipe, and curlews, splashing about in the shallow waters and pushing their long beaks into the soft mud in search of food. Thence they make their way to their respective nesting places. The plovers select the marshy spots among the hills; the snipe fly to the rushes, which fringe the edges of the neighbouring lakes; while the curlews live on the open moors, whence their shrill whistle may constantly be heard. A very fair heronry exists on one of the islands in Loch Knockie, about eight miles from Fort Augustus. The large nests can be seen nearly half a mile off. While you are on the island, the herons fly distractedly overhead, supported on their mighty wings and looking rather awkward with their long necks and legs. The golden plover, and the red and greenshanks can be seen only on the high lakes, among the mountains, where they breed. Sandpipers are most plentiful along the banks of the lakes and rivers. The handsome sea-pie, or oyster-catcher, arrives here, with its other companions, in the spring. There is only one place where it is known to breed, and that is about a mile and a half up the canal, near Cullochy Locks. The pretty moor-hen, with its red and yellow beak and long green legs, stays with us the whole year round, sometimes having the swamps all to itself.

The water-birds are fairly numerous, owing to the quantity of rivers and lakes in the district. The black-throated diver is one of the largest of these.

It is known to lay on the islands in Loch Lundi and Loch Nan Criche. The pair at Loch Lundi, however, have been conjectured to be great northern divers, but as they are very shy birds, it is almost impossible to obtain a good look at them. The eggs found there were certainly much larger than those of a black-throated diver. Red-throated divers are much more plentiful; their nearest nesting-places are Loch Tarff and Loch Knockie. One was shot not long ago by one of our boys, a short distance from the entrance of the Caledonian Canal. Cormorants are in fair quantities; nearly every day one or two can be seen flying overhead to their feeding-grounds. A pair is supposed to build on the shores of Loch Ness, but no one has yet found the nest. Six kinds of ducks either breed or visit us during the summer, namely, the mallard, widgeon, golden-eye, tufted duck, shieldrake, and teal. Mallards are very plentiful; I have seen upwards of three hundred rise together in some of the bays down the lake. The tufted duck, widgeon, and shieldrake are rare, and only seen occasionally. A few pairs of golden-eyes inhabit the lakes, and the teal is nearly as common as the mallard. The greylag goose is occasionally encountered, and is supposed to build at Loch Nan Ean, near Invermoriston. Gulls of all kinds build on any of the lakes possessing islands. The common gull is the most plentiful, and lays on Lochs Tarff, Lundi and Nan Criche. Blackheaded gulls, on the other hand, are restricted to Loch Lundi, where they keep a little corner to themselves. A pair of lesser black-backed gulls breed on Loch Nan Criche. Kitiwakes, greater black-backed gulls, and herring gulls are often seen, but they, however, prefer the west coast to lay their eggs.

The above enumeration, which is by no means exhaustive, will give some idea of the number and variety of birds which frequent our neighbourhood. The cause of this is, doubtless, to be found in the diversified nature of the country, which is thus admirably adapted to afford sustenance to our feathered friends, and enable them to supply their widely different needs.

The Abbey School, Fort Augustus, N.B.

THE GEOLOGICAL HISTORY OF THE THAMES VALLEY.

Abstract (by the author) of a Lecture delivered before the Windsor and Eton Scientific Society, on February 19th, 1891, by the Rev. A. Irving, D.Sc., Senior Science Master in Wellington College, Berks.

INTRODUCTORY REMARKS.

HE geological history of 'Father Thames' has

dwellers upon his banks. But to the geological student this interest is greatly magnified by the fact that of the larger modern river-valleys of Britain that of the

Thames (in its wider sense) is certainly one of the most ancient. Its history from the geologic standpoint is almost co-extensive with Tertiary time and all that has followed since. We shall see, as we proceed, that the Upper or Oxford Basin is a comparatively recent addition to the line of the Thames drainage; the true geological history of the Thames is identified with the line of drainage marked approximately by the valley of the Kennet, and that of the Lower Thames (below Reading). This must be regarded as the lower course (Unterlauf) of a great river whose middle course (Mittellauf) and head-waters (Sammelgebiet) were found in the great mountain-system which made the mountains of Scandinavia continuous with the once higher mountains of Brittany, the worn-down stumps of those appearing in the paleozoic and archæan rocks of the more mountainous portions of the north and west of Britain. [Reasons were given for considering this a more likely gathering-ground of the headwaters of the great Eocene river, than a hypothetical vast stretch of continental land to the west.]

The duplicate basin of the modern Thames consists of the Oxford Basin, draining chiefly Jurassic rocks; and the Lower or London Basin, in which we have only to do with the rocks of Cretaceous and Tertiary age, and with Quaternary and recent deposits. This latter basin, briefly sketched, lies in a synclinal valley of the Chalk, the chalk hills rising to 975 feet at Inkpen, the culminating point of the Kingsclere axis, and to 850 feet in the Downs of the White Horse range, no important transverse incision being made by rivers. The Kennet rises near the Chalk escarpment to the west at not more than 500 feet; the valley of this river being probably the truncated valley of the chief arterial line of drainage of Southern Eocene England. As the Chalk escarpment is cut through on the northwest, at the Pangbourne and Goring gorge, so the Chalk escarpment of the North Downs is cut through by tributary streams, which rise on or near the axis of the Weald. We pass by the question of the relative claims of the 'Seven Wells' or the 'Head of Isis' to represent the true source of the Thames,† not only because the Windrush or the Cherwell may, for length and volume of water, establish a better claim than any of the streams which rise near the escarpment of the Cotswolds above Cricklade, but much more because, from the point of view of geological history, no part of the present drainage of the Oxford Basin has any claim whatever. The Kennet-Thames line of drainage served as the channel of a much. greater volume of water than in recent times, while the present area of the Oxford Basin was drained in other directions, mainly perhaps in the direction of the Ouse, towards the old North Sea.

The succession of the British rocks, the classifica

* See "Journal of the Geol. Soc.," vol. xliv., pp. 178, 179. +See Professor Phillips, "Geology of Oxford and the Valley of the Thames," chap. iii.

tion of the Tertiaries established by Lyell, and the grounds of that classification were then briefly touched upon; and some reference was made to Prestwich's Geological Map of Europe, and to Professor Zittel's sketch-maps of the distribution of land and water in middle and western Europe in Cretaceous and Eocene times.*

It was thus briefly pointed out how the great Cretaceous sea was broken up into a number of detached areas of deposition, one such area being the Eocene Anglo-Gallic Basin, which included the south-east of England, the north of France, and Belgium; and the data, on which our knowledge of this is based, were briefly touched upon. In this basin were deposited the Lower London Tertiaries; the Thanet Beds (marine) to the east; and the Woolwich and Reading Beds, with marine shells in

FIRST DELIMITATION OF THE TAMISIAN AREA. The initiation of the movements which have taken

place along the line of the Kingsclere-Hindhead axis was the first step towards the delimitation of the Eocene Tamisian area of drainage. This may have occurred in early Eocene time, since there seems to be no clear evidence to show that the London Clay and the Bagshot Beds of the London area were ever continuous with those of the Hampshire Basin, while the diminished thickness of the London Clay, where it lies against the flank of the great anticlinal, and underlies the Bagshot Beds * (as at Highclere), points to the end of the London Clay period as the forward limit (in time) for the movement referred to. On the other hand the maintenance of a pretty constant thickness by the Woolwich and Reading

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east Kent, with estuarine shells in West Kent and East Surrey, becoming unfossiliferous, except for an occasional flora (as at Reading), in Berks. The evidence which these facts furnish of the drainage in early Eocene time, having come from the west, was dwelt upon. The numerous outliers of the Woolwich and Reading Beds, and the wide distribution of the sarsens and conglomerates, which we can identify with them, upon the present dip-slopes of the two Chalk ranges, which bifurcate towards Norfolk and Dover respectively, and even beyond the present principal escarpment of the Chalk (as at Avebury), tell of the enormous extent of this ancient Eocene estuary, which Sir Andrew Ramsay has compared, in extent and importance, with the modern estuaries of the Ganges and of the Amazons. †

"Aus der Urzeit" (Oldenbourg, Munich), Tafn. iii. and iv. "Phys. Geol, of Great Britain" (5th ed.), p. 247.

Beds and their lithological similarity in Berks and Hants, seem to tell us that no important movement along the axial line occurred during the period of their deposition. The small areal range of outliers of London Clay on the Chalk Hills of Oxfordshire, Bucks and Herts to the north, and of Hants, Berks, Surrey and Kent to the south, affords another indication of the diminution of the area of deposition of the London Clay as compared with that of the formations which preceded it.

As is often seen to be the case, these initial movements on the southern line of elevation, and probably movements on a Mercian line of elevation also, had their counterpart in a corresponding depression of the intermediate synclinal, which was gradually filled with the sedimentary deposits, wbose accumulations have given us the London Clay.

• "Journal of the Geol. Soc.," loc. supra cit.

The causes of such differential movements of parts of the earth's lithosphere were briefly discussed, and referred to contraction of the crust as the prime factor. The Kingsclere-Hindhead axis of elevation, like the Wealden axis of elevation which was connected with it later on, was thus regarded as a slight wrinkle in the crust, or one of a series of slight wrinkles, determined by the slight circumferential approximation of the two great stable archæan and paleozoic masses of Central Europe and France on the one side, and of the north and west of Britain on the other; the weaker and newer strata of the intermediate area getting pinched up and slightly folded. This was shown to be strictly comparable with the effect of the later Tertiary movements of the Alpine chain upon the intervening Secondary and Tertiary strata, as indicated in the section across the Upper Po-Basin, which the author has recently received from Professor Sacco, of Turin.*

The estuarine character of the London Clay, and its gradual passage upwards from deposits having the character of those of a marine estuary to those of a more constricted river-mouth, were pointed out; and the evidence adduced from Foraminifera by Professor Rupert Jones, and from the fauna and flora in general by Professor Prestwich, as to the depths of the waters, in which the deposits were laid down, were briefly discussed. The significance of the distribution of septaria and a molluscan fauna chiefly in the lower 200 to 300 feet of the formation, as discussed by the lecturer several years ago,† was also pointed out, as well as the indications which the organic remains give of the prevalence of a tropical or sub-tropical climate in Eocene times. Ascertained thicknesses of the London Clay, beneath the overlying Bagshots (i) at Hampstead 300 feet, at Wokingham 270 feet, at Bearwood 250 feet, (ii) at Wellington College 330 feet, at Brookwood 370 feet (or more), at Chobham Place 400 feet, at Claremont 450 feet, and at Wimbledon 430 feet, were cited as indications that the line of greatest depression during the London Clay period was some miles further south than the present line of the Lower Thames. The areal extension of the London Clay, and its gradation of thicknesses from east to west, tell us that the area of depression was a synclinal with its axis inclined to the east; in other words, it took the form of a segment of a cone rather than of a cylinder, forming what Sacco has called a "cone of depression " ("cona di déjezione."). The elevation of the KingsclereHindhead axis subjected the Chalk strata first to the action of sea-waves, which manufactured from its flints the numerous pebbles found in the Reading beds, as well as the few which are scattered through the London Clay; and we should probably not be far

"La Geo-tectonique de la Haute Italie Occidentale," "Bull. de la Soc. Belge de Geologie, &c.," tome iv., 1890. † See "Geol. Mag.," 1886, No. 9, on "The Unconformity between the Bagshot Beds and the London Clay."

wrong if we considered the denudation of the Weald as having in places cut through the Upper Chalk by the close of the London Clay period; but we have no evidence to show that the Wealden elevation at this early stage was anything more than a part of a plateau-like region similar to that on the Mercian side of the Tamisian area. For all we know it may have been such, and have continued to rise, without much change in its contour-details through the whole of the Eocene, Oligocene, and Miocene periods, until the Wealden anticline proper began to take its shape in the Pliocene period. We shall return to this later on.

CONDITION OF THINGS IN LATER EOCENE TIME.

The established attenuation of the sands which are known as Lower Bagshot, which in many of the more central parts of the area seem to form an upward extension of the London Clay formation, and which Professor Prestwich has recently correlated on such grounds with the London Clay under the name of the "London Sands," tells us of the further accentuation in later Eocene time of the structural features already initiated, as we have seen, for the south of England; while the fact, that either these sands, or the overlapping Bagshot beds of higher horizons, rest upon the lower portions of the London Clay with molluscan remains and septaria along the northern flank of the area, affords indication of the progressive accentuation of the synclinalt during the portion of geologic time indicated by those deposits. Silting up proceeded; things seem to have become stationary for a period; deltaic clays and lagoondeposits were laid down, certainly from as far west as Newbury, to a long distance towards the east, as far, at least, as Essex, as indicated by the section through Brentwood Common, recently published by Professor Prestwich.

Wokingham, Bracknell, Warfield, § and possibly Windsor Park itself, were mentioned, as localities where this transgressive relation of the Bagshot strata to the London Clay seems to be indicated; while further east, at Hampstead || and Brentwood¶ a similar relation of things can be traced. On the south side of the Eocene formations of the Tamisian area the high dip of the strata has led to more extensive denudation, and so we cannot adduce such good evidence; nevertheless there are reasons for regarding certain outlying masses of Tertiary sands

Journal of the Geol. Soc.," February, 1888.

+ Such a progressive accentuation of a synclinal flexure has been well worked out in the case of the basin of the Po by Dr. Sacco of Turin. See his valuable paper, Classification des Terrains Tertiaires," "Bull. de la Soc. Belge de Geologie," &c., tome i., 1887. In that region the accentuation seems to have gone on intermittently all down through Tertiary time, while in the Thames area it appears to have been intercepted by elevation at the end of the Eocene.

Journal of the Geol. Soc.," vol. xlvi., Pl. vii., Fig. 5. See the author's papers, ibid., vols. xliii., xliv. "Mem. Geol. Survey," vol. iv., p. 309.

Prestwich," Journal Geol. Soc.," loc. cit.