pendulums, and at every disturbance the movement of one will predominate. From this Rossi argues that the character of the microseismical motions is not constant.

Bertelli observed that the direction of oscillation of the pendulums is different at different places, but each place will have its particular direction dependent upon the direction of valleys and chains of mountains in the neighbourhood. Rossi shows that the directions of movement are perpendicular to the direction of lines of faults, the lips of these fractures rising and falling, and producing two sets of waves, one set parallel to the line of fracture and the other perpendicular to such a direction. These movements, according to Bertelli, have no connection with the wind, rain, change of temperature, and atmospheric electricity.

The disturbances, as recorded at different towns, are not always strictly synchronous, but succeed each other at short intervals. If, however, we take monthly curves of the disturbances as recorded at different towns in Italy, we see that these are similar in character. The maximum disturbances occur about the winter solstice and the minimum about the summer solstice, and in this respect they show a perfect accordance with the curves drawn by Mallet to show the periodicity of earthquakes.

At Florence before a period of earthquakes there is an increase in the amplitude and frequency of vertical movements. The vertical movements do not appear to come in with the horizontal barometrical disturbances, but they appear to be connected with the seismic disturbances. They are usually accompanied with noises in the telephone, but as the microphone is so constructed as to be more sensitive to vertical motion than to horizontal motion, this is to be expected. This vertical motion would appear to be a local action, inasmuch as the accompanying motions of an earthquake which originates at a distance are horizontal. Storms of microseismical motions appear to travel from point to point. Sometimes a local earthquake is not noticed on the tromometer, whilst one which occurs at a distance, although it may be small, is distinctly observed. To explain this, Beitelli suggests the existence of points of interference and the existence of nodes.

Similar results were arrived at by Rossi when experimenting at different points on the sides of Vesuvius. Galli noticed an augmentation in microseismic activity when the sun and moon are near the meridian. Grablovitz found from Bertelli's observations a maximum two or

three days before the syzigies, and minimum three days after these periods. He also found that the principal large disturbances occurred in the middle of periods separating the quadrature from the syzigies, the apogee from perigee, and the solstice period from the nodes, whilst the smallest disturbances happened in the middle of periods opposed to these.

P. C. Melzi says that the curves of microseismical motions, earthquakes, lunar and solar motions, show a concordance with each other. With the microphone Rossi hears sounds which he describes as roarings, explosions, occurring isolated or in volleys, metallic and bell-like sounds, ticking, &c., which he says revealed natural telluric phenomena. These are sometimes intolerably loud. At Vesuvius the vertical shocks corresponded with a sound like volleys of musketry, whilst the undulating shocks gave the roaring. Some of these sounds could be imitated artificially by rubbing together the conducting-wires in the same manner in which the rocks must rub against each other at the time of an earthquake, or by placing the microphone on a vessel of boiling water, or by putting it on a marble slab and scratching and tapping the under side of it.

These then are some of the more important results which have been arrived at by the study of microseismic motions. One point which seems worthy of attention is

that they appear to be more law-abiding than their violent relations, the earthquakes, and as phenomena in which natural laws are to be traced they are certainly deserving of our attention. As to whether they will ever become the means of forewarning us against earthquakes is yet problematical. Their systematic study, however, will enable us to trace the progress of a microseismic storm from point to point, and it is not impossible that we may yet be enabled to foretell where the storm may reach its climax as an earthquake. This, I believe, is a view held by Prof. de Rossi.

Before the earthquake of San Remo, on December 6, 1874, Rossi's tromometer was in a state of agitation, and similar disturbances were observed at Livorno, Florence, and Bologna. Since February, 1883, I have observed a tromometer in Japan, and such results as have been obtained accord with results obtained in Italy.

The increase in microseismical activity with a fall of the barometer is very marked. The style of the pendulum does not always oscillate about the same point-there is a deflection in the vertical. In Manila Father Faura also makes observations with a tromometer, which I am told gives him by movements very decided indications of approaching typhoons.

As to the cause of tromometric movements we have a field for speculation. Possibly they may be due to slight vibratory motions produced in the soil by the bending and crackling of rocks produced by their rise upon the relief of atmospheric pressure. If this were so, we should expect similar movements to be produced at the time of an increase of pressure.

Rossi suggests that they may be the result of an increased escape of vapour from molten materials beneath the crust of the earth consequent upon a relief of external pressure. The similarity of some of the sounds which are heard with the microphone to those produced by boiling water are suggestive of this, and Rossi quotes instances when underground noises like those which we should expect to hear from a boiling fluid have been heard before earthquakes without the aid of microphones. One instance was that of Viduare, a prisoner in Lima, who, two days before the shock, 1824, repeatedly predicted the same in consequence of the noises he heard

A possible cause of disturbances of this order may be the sudden fluctuations in barometric pressure which are visible during a storm.

In addition to the observations which have been especially made for the purpose of recording earth tremors, there are numerous observations which have been made upon these disturbances when they have appeared as intruders in investigations on other subjects. Amongst these may be mentioned the endeavours to measure changes in the vertical, as for instance those which might be produced by the attractive influence of the moon.

Prof. Zöllner, who invented the horizontal pendulum, found that the readings of his instrument were always changing.

M. d'Abbadie, who for several years observed a reflected image in a pool of mercury contained in a basin of solid rock, found it a rare occurrence that the surface of the mercury was tranquil. Sometimes it appeared to be in violent motion.

George and Horace Darwin, in their experiments at Cambridge to determine the disturbing influence of gravity by lunar attraction, found that the irregular and persistent tremors in the ground, as indicated by the instruments, were sufficient to mask whatever effects may have been due to the influence of the moon.

A full account of these latter observations is to be found in Messrs. G. and H. Darwin's Report for 1882 to the British Association.

The general conclusion, then, is that from observations in England, France, Germany, Italy, the Philippines,

Japan, and, I may add, the West Indies, it would appear that the crust of the globe is practically in a constant state of tremor. The variations in these movements are more law-abiding than the large earth movements, and they show a direct relationship to barometric fluctuation.

Their relationship to many other telluric and atmospheric phenomena, together with their cause, has yet to be discovered. As every one has the opportunity to observe these phenomena, they call for attention. Just as a turbulent sea outraces a coming typhoon and gives mariners warning of approaching danger, it is possible that these microscopic disturbances of the soil may hold connection with subsequent phenomena, and lead us by their study to the better understanding of the complexity of phenomena with which we are surrounded.

THE MECHANICAL THEORY OF MAGNETISM IF Prof. Hughes were as great a master of writing English as he is of experimenting, his views on magnetism would receive speedier acceptation, for they would then probably be understood without that close study which his involved sentences and heterogeneous paragraphs now demand. It is very remarkable that such an ardent worker, such a deep thinker, and such a clear and simple experimenter should have such difficulty in expounding his views on paper. His experimental demonstrations are always clear and convincing, his recent lecture at the Royal Institution appealed to every degree of intelligence present, but his papers at the Royal Society want some strong external directing influence to render their meaning evident.

What is magnetism, according to this expert philosopher? It is an inherent quality of the molecules of matter, as determined and constant as that of their gravity, affinity, or cohesion, and like these qualities it differs in degree with every kind of matter. He does not attempt at present to define it closer than this. We cannot tell what gravity is, neither need we say what magnetism is. All Prof. Hughes says is that every molecule in nature is a little magnet imbued with a certain polarity varying in degree but constant for each substance, in virtue of which it has a north and a south pole along the same axis, and that the only change that takes place is a change in the direction of this polar axis. When these molecules are symmetrically arranged by some external directing influence, so that all their poles lie in the same direction, we have evident magnetism. Iron becomes a magnet in virtue of the fact that its molecules are free to move under the influence of external magnetic action, while copper is not a magnet because its molecules are immovable and irresponsive to the same cause. Steel becomes permanently magnetised because its molecules are rigid, and retain the axial direction impressed upon them. Soft iron is readily demagnetised because its molecules have great freedom of motion. Coercive force is therefore

simply absence of freedom of molecular motion-it is, indeed, molecular rigidity. The extent to which the axis of polarity can be deflected from its normal direction is its point of saturation.

Evident magnetism is the symmetrical arrangement of the polarised molecules along one line; neutrality is symmetrical arrangement of the same molecules in closed curves. In both cases the sum of the magnetic influence of all the molecules is the same; but in evident magnetism it is directed outwards, in neutrality it is directed inwards. Remaining magnetism is partial neutrality. The experimental way in which Prof. Hughes demonstrated these conclusions is the most beautiful investigation he has yet made. He proves the existence of the same polarity in the atmosphere and in the ether, and he attributes diamagnetic effects to the higher magnetic capacity of the ether than of the substances suspended in it. It is therefore a differen

tial action. Molecules, moreover, have inertia-they resist being put in motion; and when in motion they resist stoppage-they possess momentum. The direction of the axis of polarity can be displaced by the physical forces, such as mechanical stress, heat, or electricity. He shows that mechanical motion, heat, and electricity are of similar kind-they are vibratory, or some mode of motion. Magnetism, however, he considers not to be a mode of motion, and therefore it is not a physical force. It is simply an arrangement of the molecules of matter in symmetry or dissymmetry under the influence of some physical force. He seems to imply, though he does not directly say so, that the influence of electric currents upon magnets is not due to any direct action between them, but to the fact that the currents have polarised the ether in which both are suspended.

he

His views are very broad and highly suggestive, but there are some points that are not clear and that demand further elucidation. Why, for instance, does mechanical elongation and contraction take place when bars of iron are magnetised and demagnetised ? How can heat and strong sonorous vibrations be produced unless there be a considerable expenditure of energy? How does account for the attractive and repulsive properties of magnets, and for magnetic induction? He has certainly wrested magnetism from the realms of hypothesis and brought it within the domain of theory. The days of Coulomb.and Poisson's fluids and Ampère's elementary currents of electricity are over; the molecular character of magnetism is experimentally established; but what is a molecule, and how becomes it polarised unless it be in rotation? How does the external directing influence act? We are also inclined to ask, Has Prof. Hughes sufficiently grasped Ampère's theory? It was purely mathematical, based on the assumption of the circulation of currents around each molecule. He goes no further than Ampère did, for he has not answered the question, What is polarity? In fact his polarised molecules are all little magnets, and no theory of magnetism will be complete until it explains these little magnets. Thus the difference between Ampère and Hughes is the difference between a current and a magnet.

However, on the assumption that a molecule is a magnet, Prof. Hughes has built up a very complete theory, which he has demonstrated experimentally in a way that places him in the very front rank of experimental philosophers.

NOTES

THE number of candidates up this session for the Fellowship of the Royal Society is sixty-seven.

WE understand that Sir Joseph Hooker has been nominated one of the vice-presidents for the Montreal meeting of the British Association. Instead of Mr. Crookes, Prof. W. G. Adams will give one of the public lectures. For the reduction of the fares of members the sum of 14,000 dollars has been allotted, only tho e elected at or before the Southampton meeting being entitled to share in the subsidy. This is in addition to the liberal reductions that will be made by the steamship and railway companies. All the American railways will reduce their fares by one-half. The American Association, which meets at Philadelphia on September 3, has given a cordial invitation to the Montreal vis'tors to take part in its meetings and excursions. Those wishing to share in the subsidy of 14,000 dollars must apply before September 25. For the Aberdeen meeting in 1885, Sir Lyon Playfair will be proposed as president. A well-attended meeting of the Organising Committee of the Chemical Section has been held under the presidency of Prof. Roscoe. Promises of papers were received from several well-known chemists, and a small executive committee was formed to draw up a list of papers and to communicate with Canadian and American

chemists. Section G has been particularly active. The Conmittee has prepared a list of subjects for papers which it is thought would be interesting to English visitors if treated by engineers and mechanicians in Canada; a good supply of papers is expected both from this country and America. We regret to learn that Prof. Williamson, the General Treasurer, will be unable to be present, and the Council have decided to engage the services, pro hac vice, of Mr. Hamy Brown, Assistant Secretary and Accountant of University College, as "Financial Officer," while Prof. Burdon Sanderson has virtually consented to act as deputy for the Treasurer at Montreal.

M. CARO, for the French Academy, and MM. Pasteur and d'Abbadie, for the Academy of Sciences, will attend as delegates the fêtes at Edinburgh in commemoration of the tercentenary of the foundation of the University of Edinburgh.

DR. KOCH and his colleagues of the German Cholera Com. mission will proceed shortly to Goalpara and Darjeeling to prosecute further inquiries. After passing a few days there, they will return to Germany, but they hope to be back in India next winter to carry on their very important and useful labours.

DR. GEORGE ENGELMANN of St. Louis-the oldest United States botanist (excepting the venerable Lesquereux), as well as an eminent physician, for a time a fellow-student with Agassiz in Germany-died on February 11, at the age of seventy-five.

COMMODORE SAMUEL R. FRANKLIN, U.S.N., has been de tached from duty on the United States Naval Examining Board, and ordered as superintendent of the naval observatory, to succeed Rear-Admiral R. W. Shufeldt, who was placed upon the retired list on February 21.

AT the sitting of the Academy of Sciences of March 10 M. Faye presented drawings which have been executed at Algiers by M. Trépied, Director of the Observatory, and which repre sent Pons' comet as seen on the very days on which have been noticed the changes that have excited such surprise amongst certain astronomers. M. Faye took advantage of this communication to give an explanation of these wonderful observations, which are more frequent than has been supposed in the history of astronomy. M. Faye does not suppose that they may be attributed to any collision with cosmical matter, but to a rapid change in the point of view of the comet itself, as observed from the earth. This theory will be illustrated by a woodcut published in the next number of the Comptes Rendus.

CONSIDERABLE progre s has now been made in the carrying out of the works connected with the marine station which some time ago the Scottish Meteorological Society resolved to establish at Granton; and it is anticipated that the oper tions of the station will be properly commenced towards the close of the present month.

As the first instalment of the work to be done, it is hoped that a tolerably complete description of the Firth of Forth, in its biological, meteorological, physical, and chemical relations, may be prepared in the course of the next few years; and when this has been carried out, the result will have an exceptional, and indeed unique value, as a piece of work of the greatest scientific and national importance, produced by cooperation amongst scientific men. The Council of the Scottish Meteorological Society, it may be mentioned, recently asked Her Majesty's Government for a subscription of 1000l. for the purpose of building permanent laboratories in connection with the station-undertaking at the same time to raise an additional 1000l. by public subscription. The Government, however, have not seen their way to assist this school of research, notwithstanding that the grant was warmly recommended by Prof. Huxley, President of the Royal Society. The Council of the Meteorological Society have, however, every confidence that the scheme will be liberally supported by the general public.

DR. CASEY, F.R.S., has just written a new work on Analytic Geometry, which covers about two-thirds of the ground occupied by Salmon's Conics; in the author's opinion it will contain more new matter than any work on the subject since Salmon's book was written.

AN interesting experiment is to be made by Dr. Zintgraff, who, in company with Dr. Chavanne, is about to visit the Congo and the interior of Africa. He takes with him a phonograph, wherewith to fix the speech and melodies of hitherto unknowu tribes, which, thus received by the instrument, will be forwarded to scientific men in Germany. The apparatus (which will be used for such a purpose for the first time) has been made by Mr. Fuhrmann, of Berlin, and exactly corresponds with one he has in that city, so that the plates used in Africa can be sent to Berlin to be unrolled by that machine, and caused to re-emit the sounds received.

A REMARKABLE occurrence is reported from Bona (Algeria). An isolated mountain, Jebel Naiba, Soo m. in height, is rapidly decreasing in altitude, and round its base a considerable cavity is being formed. The whole mass of the mountain is evidently sinking. The neighbourhood of Bona must, however, have already been the scene of a similar phenomenon. Lake Fezzara, which measures over 12,000 hectares in extent, did not exist during the time of the Romans. Its depth in the centre is only 260 m. Investigations which were made in 1870 showed that the remains of a Roman town now lie in the lake; this town has therefore probably sunk in the same manner as the mountain.

A PREHISTORIC burial-ground has been discovered on the socalled Hasenburg, near Buhla (Kreis Nordhausen, Germany). Two complete human skeletons, numerous bronze rings, and several rings made of amber were found. The Hasenburg is an isolated rock on which stood formerly a castle of the Emperor Henry IV.; but the numerous prehistoric remains found in the neighbourhood point to its having been an ancient place of worship. The objects recently found have been deposited in the Museum of Nordhausen.

THE appointment by the Swedish Government of an entomologist to assist farmers has been found of so much value that it has been decided to continue the same. Dr. A. Holmgren has been appointed agricultural entomologist for this year.

THE city of Hamburg offers various prizes for the plans of a new Natural History Museum. The total cost of construction of the building must not exceed 45,000l. Five prizes of 50%. each will be awarded for the five best plans; further prizes of 2007, will be distributed amongst the victors for further work in connection with the scheme.

AT a recent meeting of the Straits Branch of the Royal Asiatic Society at Singapore, it was decided to prepare and publish a school geography of the Malay peninsula and the adjoining regions, as well as a skeleton map of the peninsula, on a scale of a quarter of an inch to a mile, to be gradually filled in as may be determined by subsequent survey and research.

DR. BENJAMIN SHARP has been appointed Professor of Lower Invertebrata by the Council of the Academy of Natural Sciences of Philadelphia. Dr. Sharp is a graduate of the University of Pennsylvania, from which he received the degrees of Doctor of Medicine and Doctor of Philosophy in 1881. He afterwards studied under Leuckart in Leipzig, and under Semper in the University of Wurzburg. Dr. Sharp was granted the privilege of studying at the Bavarian table in the Zoological Station at Naples, an honour rarely granted a foreigner. Dr. Sharp proposes delivering lectures, during the coming spring, on the lower forms of life.

March 13, 1884]

PROF. KARPINSKY points out, in the Memoirs of the St. Petersburg Society of Naturalists (vol. xiii.), the following interesting The unmetafeature of the geological structure of Russia. morphosed rocks in Russia appear mostly quite, or nearly quite, undisturbed and horizontal. There is, however, besides the Crimea, a region where some dislocation and disturbance of these deposits are apparent. This disturbed region runs from northwest to south-east, through the Sandomir ridge in Poland to Kaneff in Kiev, Isakchi in Poltava, the coal-basin of the Don, the Bogdo Mountains of the Astrakhan Steppe, and finally to the Kara-tan and Ak-tan Mountains to the east of the Caspian. Beyond this region even the older deposits (Silurian and Devonian) remain undisturbed, while within it the older gneisses and crystalline schists are disturbed, not only by the Silurian upheaval which has had a direction from north-east to south-west, but also by the more recent one just referred to, which has a direction perpendicular to it. It is worthy of notice that this line of upheaval would join that line of ridges which runs in Western Europe through the mountains of the Weser and the Teutoburger Wald, while in Asia it would join the Sheikh-jeli and Uiz-Dagh Mountains.

WE notice in the same serial some very valuable observations of Prof. Beketoff about Dr. Sachs' theory as to the relations between the increase and segmentation of cells in the embryonal parts of plants. While he warns one against the application of geometrical theories to botany, he points out how some of the conclusions arrived at by Dr. Sachs could be more easily explained by the principles established by Wilhelm Hofneister. Prof. Borodin's researches into the anatomy of the leaves of Chrysosplenium were made on very rich material collected by Prof. C. Maximowicz for his "Adumbratio Generis Chrysosplenii," and Prof. Borodin was enabled not only to thoroughly study the subject, but also to arrive at some most valuable conclusions as to the relations between the anatomical features of different species of this genus and the features on which the classification of these species has been made.

TRACES of glaciation in Siberia, so boldly denied a few years ago, have been discovered in different parts of the country. While failing to detect them on the outer parts of the Altai Mountains, M. Sokoloff has found unmistakable traces of an incomparably wider extension of glaciers in the central parts of the ridge, and especially in the Katun Mountains. traces have also been found, pointing to a greater extension of lakes during the post-Glacial period, and to the gradual drying up of the existing ones.

Numerous

As the

MR. E. L. LAYARD writes to us from Noumea, New Caledonia, under date Jan. 6, that the sunsets there have been quite as extraordinary as elsewhere. "As soon," he says, "as the sun's disk has disappeared, a glow comes up from the west like that of white-hot steel, reddening somewhat as it mounts to the zenith, but changing the while to blue. From the zenith it passes into the most exquisite green, deepening as it loses itself in the east. sun sinks lower and lower, the red tints overpower the whitehot steel tints, and the blue of the zenith those of the green. At 7 p.m., or a little after, nearly the entire western half of the horizon has changed to a fiery crimson; as time goes on, the northern and southern areas lose their glory, and the grays of night contract, from the northern end first, most rapidly; the east is of the normal gray. The south now closes in, and presently, about 8 p.m., there is only a glare in the sky, just over the sun's path as of a distant conflagration, 'till the fire in the west fades out.' I have been attempting to describe one of our cloudless evenings, of which we have had only too many, having just come through a fearful drought that has lasted all this while; but who shall paint the glory of the heavens when flecked with clouds! Burnished gold, copper, brass, silversuch as Turner in his wildest dreams never saw! and of such

fantastic forms! The wonderful light from above was reflected on every tree and flower; our scarlet and crimson geraniums, fuchsias, &c., blazed in the light as I never saw them before, and the general effect was most extraordinary."

THE Cremation Society of Berlin now numbers 365 members, no less than 146 having joined the Society during 1883. The cremation movement is also progressing favourably at Hamburg, At Gotha Königsberg, Dresden, Breslau, and Wiesbaden. forty-six bodies were cremated during 1883, which is about double the number of those burnt in any of the four preceding years.

THE additions to the Zoological Society's Gardens during the past week include a Bonnet Monkey (Macacus sinicus ?) from India, a Pig-tailed Monkey (Macacus nemestrinus ? ) from Java, presented by Mr. G. H. Lee; two Herring Gulls (Larus argentatus), European, presented by Madam Fridaich ; a Kagu (Rhino

seen issuing from the summit of the volcano; and in the daytime vast volumes of smoke roll from it. Upon nearer approach from English Harbour it was found that the mountain had been split in two from peak to base by a great rupture extending across it from east to west, and that the northern slope of the mountain had sunk away to the level of the northern cliff.1 This is corroborated by the statement of the hunting-party in Kamishak Bay. Smoke issued from the peak at a very short distance to the southward of the rupture.

The party of natives on Kamishak did not approach the islet, though they gave clear and distinct accounts of its eruption and subsequent appearance; but Capt. C. T. Sands, who was at English Harbour, gave the Alaska Company a full description; and Capt Cullie, of the Kodiak, states that, if there were plenty of water in the line of rupture, it would be possible for a vessel to sail through. At the time of Capt. Sands' observations the low ground of the island was visible, and seemed to be a vast crater, from which smoke and flames were issuing.

But beyond all these phenomena, apart from the volcanic eruption and the rupture of the island, we have the report of Capt. Cullie, of the schooner Kodiak (from whom we also obtain a statement in regard to the rupture), who approached the island from English Harbour on November 10, and found that a new island about a mile and a half long and seventy-five feet high, had been upheaved in the ten-fathom passage between Augustin and the mainland to the westward. This passage is from six to eight miles wide, and was sailed through by Puget in Vancouver's voyages of discovery.

This new island (also reported by the hunting-party in Kamishak) would appear to have arisen during the late volcanic activity. It lies to the north-westward of Chernaboura Island (Augustin), and was distinctly seen from the Kodiak, as that vessel lay ten miles to the north-eastward, and had clear weather.

To show the violence of the volcanic convulsions at this time, two extinct volcanoes on the Alaska peninsula, which are reported to be about west (true) from the active volcano Iliam na (twelve thousand feet high), had burst into activity; and during the day volumes of smoke were distinctly seen, and columns of flame at night. Usually, at that season, Augustin and the peak are covered with deep snow. On November 10, however, when Capt. Cullie app reached the island, while there was a depth of four feet of snow at Port Graham (English Harl our), Mount St. Augustin was bare and black.

GEORGE DAVIDSON,

Assistant U.S. Coast and Geodetic Survey

THE ORIGIN OF THE SCENERY OF THE BRITISH ISLANDS 2

TH

HE Plains of Britain, like those elsewhere, must be regarded as local base-levels of denudation, that is, areas where, on the whole, denudation has ceased, or at least has become much less than deposit. Probably in all cases the areas they occupy have been levelled by denudation. Usually a greater or less depth of detrital material has been spread over them, and it is the level surface of these superficial accumulations that forms the plain. But in some instances, such as the flats of the Weald Clay and the Chalk of Salisbury Plain, there is hardly any such cover of detritus, the denuded surface of underlying rock forming the actual surface of the plain. Our plains, if classed according to the circumstances of their origin, may be conveniently regarded as (1) river plains-strips of meadow-land bordering the streams, and not infrequently rising in a succession of terraces to a considerable height above the present level of the water; (2) lake plains-tracts of arable ground occupying the sites of former lakes, and of which the number is ever on the increase; (3) marine plains-mostly flat selvages of alluvial ground, formed of materials originally laid down as a littoral marine deposit when the land lay below its present level: in the northern estuaries these up-raised sea-beds spread out as broad carse-lands, such as those of the Tay, Forth, and Clyde; (4) glacial drift plains-tracts over which the clays, sands, and gravels of the Ice Age form the existing surface; (5) submarine plains-the present floor of the North Sea and of

the Irish Sea, which must be regarded as essentially part of the terrestrial area of Europe.

When plains remain stationary in level, they may continue for an indefinite period with no material change of surface. But, should they be upraised, the elevation, by increasing the slope of the streams, augments their erosive power, and enables them once more to deepen their channels. Hence, plains like that of the New Forest, which have been deeply trenched by the watercourses that traverse them, may with probability be assigned to a time when the land stood at a lower level than it occupies at present. In this connection the successive river-terraces of the country deserve attention. They may be due not to the mere unaided work of the rivers, but to the cooperation of successive uplifts. It would be an interesting inquiry to correlate the various river-terraces throughout the country, for the purpose of discovering whether they throw any light on the conditions under which the most recent uprise of the country took place. That the elevation proceeded intermittently, with long pauses between the movements, is shown by the succession of raised beaches. It may be possible to establish a somewhat similar proof among our river-terraces.

The submarine plains are by far the most extensive within the British area. In the case of the North Sea the tendency of tidal scour and depcsit must mcdify the form of the bottom. This great basin of water is obviously being slowly filled up by the deposit of sediment over its floor. A vast amount of mud and silt is borne into it by the rivers of Western Europe, as well as by those that drain the eastern and larger part of Britain, and the sea itself is cutting away the land on both sides and swallowing up the waste. We have only to contrast the colour of the Atlantic on the west of Ireland or Scotland with that of the North Sea to be assured of the wide diffusion of fine mud in the water of the latter. There is practically no outlet for the detritus that is thus poured into the basin of the North Sea. From the north a vast body of tidal water enters between Scotland and Norway, and travelling southward, aided by the strong northerly winds, sweeps the detritus in the ame direction. On the other hand, another narrower and shallower tidal stream enters from the Strait of Dover, and, aided by the south-west winds, drives the sediment northward. Yet, making every allowance for the banks and shoals which this accumulating deposit has already formed, we can still, without much difficulty, recognise the broader features of the old land-surface that now lies submerged beneath the North Sea. It presents two plains, of which the southern has an average level of perhaps a little more than 100 feet below the surface of the water. This upper plain ends northward in a shelving bank, probably the prolongation of the Jurassic escorp ment of Yorkshire, and is succeeded by the far wider northern plain, which lies from ICO to 150 feet lower, and gradually slopes northward. As mentioned in a previous lecture, the drainage lines of the united Rhine, Thames, &c, cn the one side, and the Elbe, Weser, &c., on the other, can still be partially traced on the sea-floor. The Irish Sea was probably, in its later history, a plain dotted with lakes. It appears to have been submerged before the whole of the present fauna and flora had

reached Ireland.

:

Some of the most characteristic and charming scenery of the British Islands is to be found along their varied sea-board. Coast-scenery appears to dep end for its distinctive features upon (1) the form of the ground at the time when by emergence or submergence the present level was established; (2) the compo ition and structure of the shore-rocks; (3) the direction of the prevalent winds, and the relative potency of subaerial and marine denudation. The British coast-line presents three dis tinct phases in many places it is retreating; in others it is advancing; while in a few it may be regarded as practically stationary. As examples of retreat, the shores of a large part of the east of Englard may be cited. In Holderness, for instance, a strip of land more than a mile broad has been carried away during the last eight centuries. Even since the Ordnance Survey maps were published, thirty-three years ago, somewhere about 500 feet have in some places been removed, the rate of demolition being here and there as much as five yards in a year. The advance of the coast takes place chiefly in sheltered hays, or behind or in front of projecting headlands and piers, and is due in large measure to the deposit of material which has been removed by the sea from adjoining shores. The amount of land thus added does not compensate for the quantity carried away, so that the total result is a perceptible annual loss. The best examples of a stationary coast-line where there is no appre