ZÖPPRITZ ON OCEAN currentS

I SEND you a translation by a friend of an important contribution to the theory of ocean currents by Prof. Zöppritz, of Giessen, which has recently appeared in the Annalen der Hydrographie und Maritimen Meteorologie. The mathematical part of the subject has been published in the Annalen der Physik for April last, a translation of which will be found in the Philosophical Magazine for September.

One of the main objections urged against the theory that ocean currents are due to the impulse of the winds is that the winds can, it is alleged, produce only a surface drift, whereas many of the currents extend to great depths. I have always maintained that this objection is totally erroneous; that if the surface of the ocean be impelled forward with a constant velocity by the wind or by any other cause whatever, the layer immediately below will be dragged along with a constant velocity somewhat less. The layer underneath this second layer will in turn be also dragged along with a velocity less than the one above it. The same will take place in regard to each successive layer, the velocity of each being somewhat less than the one immediately above it, and greater than the one below it. In this manner the surface velocity may be transmitted downwards to any depth. This conclusion has now been demonstrated by Prof. Zöppritz, in the following paper, to be perfectly correct. JAMES CROLL

Though for a long time the majority of seamen and geographers have firmly held the opinion that the great equatorial ocean currents derived their origin from the trade winds, yet, so far as I know, no attempt has yet been made to treat the physical problem of the propagation of surface-velocities downwards through a very thick stratum of water, with the means presented by the theory of the friction of fluids, as elaborated within the last thirty years. Such an attempt is all the more demanded as many authors have lately denied that surface-forces could set the sea in motion to any considerable depth. At the same time the most groundless assumptions have been set forth as to the depth of such drift-currents.

The essential principle of the theory of the internal friction of fluids is that when a plane stratum of water is moved forward, by any cause, in its own plane with a given velocity, the adjoining stratum cannot remain at rest, but, in consequence of its molecular cohesion experiences an impulse to move in the same direction. And if the velocity of the former stratum be continuous the latter assumes a velocity which tends to approximate con. stantly to the given velocity. This second stratum now exerts the same influence on a third adjoining stratum that it had to suffer from the first, and sets it in motion in the same direction. The third stratum draws with it in a similar manner a fourth, fourth, a fourth a fifth, and so on. The propagation of the velocity is only bounded by the limits of the fluid itself. If these limits consist of a solid plane parallel to the strata, then the propagation of the velocity will cease only at this point, i.e., between the last liquid stratum and the first solid stratum.

The law according to which two neighbouring strata of velocities mutually influence one another has already been demonstrated by Newton, and the accelerating force exerted by the friction has been assumed as inde. pendent of the pressure and proportional to the difference of velocity. The later thecry of the friction of fluids carries out this fundamental hypothesis as to the propagation of velocity between strata of the same medium which lie at an indefinitely small distance & from one another, and have accordingly only an indefinitely small difference of velocity A, inasmuch as it makes the acceleration produced by the friction, at the plane in which the strata meet, proportional to the quotient A : ξ. The factor k, by which this quotient must be multiplied

in order to give the acceleration, is called the Coefficient of Internal Friction.

The Newtonian hypothesis can be applied likewise to those parts of the bounding-surfaces of the fluid (where it is in contact with other bodies) which may possess independent motion. Here the acceleration produced by the limiting medium (which may be solid, fluid, or gaseous) is proportional to the difference of velocity which may in this case be finite. The factor of the proportion is called the Coefficient of External Friction. If the bounding body is a solid or even a fluid, then the fluid may wet it, that is, the stratum of fluid touching the limiting body may cling so fast to that body as to assume the same velocity. The coefficient of external friction is in this case infinitely great. This is the case between wood and water, glass and water; and, on the other hand, not so between glass and quicksilver.

The theory founded on this simple hypothesis has been subjected to the most varied experimental tests, and has, on the whole, been found to agree with the facts, so that the hypothesis may be regarded as proved.

In order to apply this theory to ocean currents, the simplifying presupposition has been made that the ocean is a mass of fluid contained between two horizontal planes at the distance h from one another, but in other respects unbounded. On the surface of this mass of fluid a wind of uniform strength and direction is acting at all times, while the under-surface wets a solid plane, the seabottom, and is therefore always at rest.

We must not, however, look on the action of the moving air on the surface stratum of the water as proceeding according to the Newtonian hypothesis; it will act in this way only so long as the surface remains level.

But the wind produces waves and acts on them according to quite different laws. One fact of experience is available here, viz., that the surface-stratum of the ocean under the influence of a uniform wind, moves in the direction of the wind with a constant velocity dependent on the strength of the wind. If, therefore, we place on the velocity of the water at the surface the condition that it has a value wo at all times given, everywhere uniform, and of uniform direction, then the problem of the determination of the internal velocity becomes soluble.

But the simplifying presuppositions here assumed are almost realised in the central equatorial regions of the great ocean; the solution of the problem becomes, therefore, of deep interest.

The following are the chief results of the solution :If for an infinitely long time the surface-stratum has been kept at an unchanging velocity, then the whole mass of water is in a steady state of motion, i.e., a state which no longer varies according to the time. The velocity wis then dependent only on the depth x beneath the surface, and diminishes in proportion as the depth increases, till at the bottom it reaches zero. This relation is expressed by the formula

w = w

h-x h

state of motion that prevails after an infinitely long time the distribution of the velocity is the same in a thin fluid like water and in a thick fluid like syrup. In the fixed state of motion the influence of friction is shown by the participation of all the strata in the motion which is imparted from without to the surface alone. Dependence on the coefficient of friction takes place only on the consideration of motions that vary with the time, and affords a measure for the depth of penetration of a surfaceimpulse within a given tim

The formula which gives the velocity at the depth x of

A maximum and the following minimum of the annual oscillation always exist at the same time at a vertical distance of 11.9 metres.

To give a conception of the time that a constant surface-velocity which begins at the time t = o requires, in order to bring the interior of an ocean 4,000 metres deep, which was previously at rest, to the state of steady motion, the following numbers will serve : -After 10,000 years there prevails at the half-depth, i.e., at x = 2,000 metres, just the velocity 0.037w. Since, according to the already-stated formula, in the steady state the velocity

the surface has been kept at a constant velocity wo, has naturally a less simple form than the formula which was found for steady motions. (The formula is the same as that which determines the propagation of heat in a solid wall whose one side is kept at a temperature wo, whilst the other remains at oo.) From this formula results the simple law that any velocity whatever between o and wo prevails at different times at depths which are related to one another as the square roots of the times. I have used the formula to compute the time that a point at the depth of 100 metres requires to attain half the surface velocity, i.e., & Wo. The coefficient of friction of the water was assumed according to O. E. Meyer's determination, at 00144, in which centimetres and seconds are the units of calculation. The result was that 239 years are required for the layer of water 100 metres deep to assume the half of the surface velocity. If it be asked what length of time is required for one-tenth of the surface velocity to penetrate to that depth, the answer is 41 years. Accordingly, the same velocities will be attained at a depth of 10 metres after 2.39 and 0'41 years respectively. In a more viscous fluid the resulting numbers would be

smaller.

These numbers are well calculated to give an idea of the slow rate at which changes of motion are propagated downwards. For the numbers computed for the propagation of a given surface motion, hold likewise for the penetration of a change of the motion from the surface downwards, whose influence is simply added to the already existing motion. A steady current, therefore, whose velocity diminishes linearly according to the depth, will sustain only an extremely slight alteration (except in the strata nearest the surface) from passing changes of motion that affect the surface, e.g. from contrary winds or storms. There will prevail, rather, at every deeplying point of this current, a mean velocity that changes only very slightly according to the time, and which is determined by the mean velocity at the surface. This latter velocity has the direction of the prevailing wind, according to whose strength it varies by a law that cannot be more accurately settled.

If the surface velocity varies periodically according to the time, as is the case with all winds that depend on seasons and the hours of the day, then, after this periodic state has lasted an infinitely long time, the velocity at all depths is a periodic function of the time of similar period, but such that the amount of variation decreases rapidly according to the depth and that the occurrence of the maxima and minima is delayed proportionally to the depth. At a depth of 10 metres the amount of the yearly oscillation is already diminished to less than 13th; at a depth of 100 metres it is beyond observation; at this depth the velocity is that corresponding to the steady state when the mean annual velocity is given to the surface. When the depths decrease in arithmetical proportion, the amounts of the oscillation decrease in geometrical proportion such that at four depths X1, X2, X3, X which stand in the relation

X4X312-1;

the amounts D1, D2, D3, D1 stand in relation D1: DD: D1.

the ocean is still removed after 10,000 years from the steady state. After 100,000 years the velocity at the depth stated is already 0 461w, therefore very near the definitive value. After 200,000 years it differs only by two units in the third decimal place.

Among the results we have found, particular emphasis is to be laid on two, which seem more or less to contradict the views which have prevailed up to this time. In the first place, the steady motion arising in the interior of an unlimited stratum of water from an unvarying surface velocity makes itself felt with linearly decreasing velocity down to the bottom. Hitherto the view frequently expressed was, that the influence of surface currents, e.g., the drift caused in the tropical ocean by the trade winds, reached only to very moderate depths. Secondly, it was found that all variations according to time, whether periodic or aperiodic, of the forces acting on the surface, propagate themselves downwards with extraordinary slowness, the periodic in very quickly decreasing amount. Taking both statements together, it follows that the movement of the chief part of a stratum of water exposed to periodically varying surface forces is determined by the mean velocity of the surface, and that the periodic variations are observable only in a comparatively thin surface stratum. From this it is obvious that hitherto the influence of the friction was undervalued in one direction, in so far, namely, as it was believed that its influence need not be considered as penetrating so deep, but in another direction it was overvalued, as too great an influence was wont to be ascribed to friction in respect of the propagation of varying current motions Its effect was also very much overvalued in another point, viz., in respect of the action of a bank on a stream flowing along it. If, I repeat, the whole surface is kept at a constant velocity, then also in the current bounded at the side the distribution of velocity in the steady state is independent of the co-efficient of friction. Beyond that, the influence of the banks on the distribution of velocity is exceedingly slight.

A further result is that two steady currents flowing parallel to one another, but in opposite directions, in a fluid-stratum of constant depth, may very well graze one another without mutual disturbance. Their surface of division is then a vertical plane parallel to their direction in which the velocity o prevails, and which, therefore, stands to each current in the relation of a solid bank.

We have already shown numerically how extraordinarily slow the velocity existing at the surface is propagated downwards when the interior was previously at rest. Hence it may be concluded, vice versa, that when every point of the whole mass of fluid has at a given moment a given velocity varying according to the depth, and when from the same moment onwards the surface remains at rest, the effect of this initial state vanishes equally slowly, i.e., the ocean passes into the state of rest with the same slowness with which in the first case the surface-velocity was propagated into the interior. In fact the formulæ show that the times for the increase and decrease of the same fraction of the given velocity are expressed by the same number.

If from some cause or other strong currents had been generated in the ocean, say 10,000 years ago, these. currents would certainly not have as yet disappeared, but would still be the chief agents in determining the movement of the ocean at great depths, supposing that the earth were completely covered by an ocean of the uniform depth of 4,000 metres.

The interruption by continents and islands of irregular form will contribute to weaken the effect of these former states of motion, not so much through the increased friction on the ocean-bed as through the reflex currents, which arise everywhere, crossing and impeding one another. But it must be observed after the above numerical proof of the extremely slow spread of local alterations of motion over the interior mass, that the difficulties of an exact computation must not be shirked, on account of the traditional expression: "Friction quickly uses up all these velocities."

It would be possible to determine by observations whether effects of former movements are still present in the ocean. There would be required for this purpose only comparative (current-observations at the most varied depths, to be applied in the central parts of the great equatorial currents and of the region of calms. Yet, however, we dare not hope to be able to detect small remnants of interior motion with the same certainty with which the effect of the former high temperature of the earth, which disappears according to the same law, could be detected by subterranean observation of temperature, were one able to penetrate deep enough with the thermometer into the earth's crust.

The above computations give us also an idea how distant must be the time of the initial state. What a long time, for example, must we imagine the trade winds to have been blowing with their present extent and strength in order to be justified in assuming that the present state of motion of the equatorial currents is steady. For that about 100,000 years are needed, supposing we postulate a mean depth of 4,000 metres and do not take into account the deadening influence of continents and islands which must somewhat diminish that number. Every initial state, whatever it may have been, vanishes finally, and gives way to a steady state, only the time varies which is required to diminish the originally arising velocity to any required degree of smallness.

OUR ASTRONOMICAL COLUMN

THE MELBOURNE OBSERVATORY. -The thirteenth official Report of the Board of Visitors of the Melbourne Observatory, with the annual statement of the Government Astronomer, is before us. Mr. Ellery reports that the new building to contain the magnetical and meteorological instruments registering continuously by photography is completed. The staff of the Observatory now consists of the director, with a chief assistant (Mr. White) and three junior assistants. The transit-circle is found to be inadequate for modern requirements, and the Board of Visitors lay stress upon the necessity of providing an instrument of greater pretensions, to enable Melbourne to co-operate effectively with European and American observers; the Sydney Observatory being already in possession of a very superior meridian-instrument, and one having been ordered, it is understood, for the observatory under the direction of Mr. Todd at Adelaide, it is hoped that a new transit-circle may soon be provided for Melbourne, and it is suggested that the necessary appropriation, about 1,200/., might be made in two annual votes, as two years will be required for the completion of the instrument.

The great reflector, though reported to be working satisfactorily, the mirrors retaining an excellent polish, and no marked signs of deterioration being visible, is occasionally subject to trifling derangements of its mechanism. Unfortunately the publication of the work

with this instrument, the drawings of nebulæ, has been

delayed by the loss of the gentleman who copied the drawings on stone. The drawings, however, now only require printing, and their publication is not likely to be long retarded. Mr. Ellery refers to the miscellaneous observations made during the year to which his report relates (to June 30, 1877), including observations of D'Arrest's comet of short period, determination of positions of stars used by Mr. Gill during his expedition to Ascension, measures of southern double stars and of the polar and equatorial diameters of Mars, and of Saturn's ring. With regard to the use of the great reflector it is mentioned, "Out of 326 available nights 150 were unfitted for observation from unfavourable weather, bright moonlight interfered on 32, while 49 were occupied with visitors, which, together with about 20 nights during which the telescope was under repair, or which were unavailable from other causes, left only 75 nights upon which observations could be made." From the observations made during the year upon 77 of the smaller nebulæ in Sir John Herschel's "General Catalogue," it is gathered that while the actual aspect of many conforms precisely with Herschel's description, others are so considerably changed as to be only recognisable by their position. The only change detected in the great nebula about η Argûs, since the drawing in March, 1875, has been " a break or separation in one of the branches on the preceding side."

Observations of the satellites of Uranus were made on sixteen nights, and on the same number of nights the satellites of Mars (the announcement of the discovery of which had been telegraphed to Mr. Ellery by Sir George Airy) were unsuccessfully sought for; the failure to find these objects with certainty and ease Mr. Ellery considers "somewhat unaccountable," but the reader will hardly need to be reminded that there are other cases where the large reflectors have not proved so adequate for work as the large refractors: sooner or later, at Melbourne or elsewhere, we hope to see a large instrument of the latter class applied to the survey of the southern heavens: the real astronomical work in the northern hemisphere, the more precise micrometrical measures and more delicate observations falling to the task of the practical astronomer, have been, as yet, pre-eminently due to the use of the refractor.

BIELA'S AND HALLEY'S COMETS.-There are near approximations between the orbits of these bodies not far from points which were first roughly indicated by Littröw, in a communication to the Vienna Academy in 1854, entitled "Bahnnähen zwischen den periodischen Gestirnen des Sonnensystemes." In heliocentric longitude 39° 25′ (equinox of 1836) the distance between the two orbits is o'032 (the earth's mean distance from the sun = 1), and in 200° 51', the distance is as small as 0011. At the former point the true anomaly of Halley's comet is - 94° 9', with the elements of 1836, and that of Biela's - 71° 17'; at 200° 51' the true anomaly of Halley's is + 104° 59′, and of Biela's + 90° 2'; we see then that on the last return of Halley's comet to these parts of space, though its orbit approached so near to that of Biela's, there was no near approximation of the two bodies. It will be remembered that Biela's comet also passes very near to the orbit of Tempel's comet 1866 I., and consequently to the track of the November meteor

stream.

GEOGRAPHICAL NOTES

AMONG the geographical notes in the January number of the new periodical issued by the Royal Geographical Society we find some interesting information regarding the work to be done by Mr. Keith Johnston's East African Expedition. He is instructed to gather data for constructing as complete a map as possible of the route, and to make all practicable observations in meteorology, geology, natural history, and ethnology, with the view of rendering as exact as possible the information obtained regarding the region, its inhabitants, and products. As special subjects of investigation he is to observe and note the routes best adapted for future more extensive communication, and to spare no efforts in examining the range of mountains seen by Mr. E. D. Young and by Capt. Elton and his party, at the north-east end of Lake Nyassa, ascertaining their extent and elevation, and the condition of the routes or passes over them. The practicability of constructing a line of telegraph from north to south through the region is also to be inquired into. If Mr. Johnston should succeed in reaching Lake Tanganyika he is directed to pay special attention to facts bearing upon the extraordinary rise in its level in very recent times, as stated by Mr. Stanley. Besides making accurate measurements, Mr. Johnston is recommended to institute inquiries as to whether the rise may not be periodical, or the result of a succession of years of excessive rainfall; but in the event of its proving continuous he is to investigate with care the causes and results of so remarkable a phenomenon. This note is followed by a summary of the survey arrangements of the Afghanistan Expedition, which promise to add much to our knowledge of the unknown tracts of country on our north-west frontier. The information contained in the remaining notes has already been placed before our readers in our own columns. The maps in the present number are those of the Fly River, New Guinea, from Signor D'Albertis' survey, of the Sulimani Mountains, on our Afghan frontier, illustrating an article by Mr. C. R. Markham, and of the routes of the Swedish and Dutch Arctic Expeditions.

THE International African Association at Brussels have recently received intelligence that MM. Wautier and Dutrieux, with 360 porters, had left Mpwapwa on October 15 to rejoin M. Cambier. On October 27 they were at Mvumi, in Ugogo, where a letter from M. Cambier reached them, announcing his arrival at Kasisi, which is two days' march from Urambo, the capital of King Mirambo, of Unyamwesi. They are now travelling in company with M. Broyon, Mirambo's son-in-law, who is said to be taking up a large convoy to Ujiji for the English missionaries, and under his able guidance and advice it may be hoped that they will escape similar misfortunes to those which they have experienced in the past.

INTELLIGENCE has been received at St. Petersburg that Prof. Nordenskjöld's steamer Vega is ice-bound on the Siberian coast.

In the last number of the Tour du Monde, M. Alfred Marche, the former companion of M. Savorgnan de Brazza, in his explorations of Western Africa, concludes his admirably illustrated chapters, entitled "Voyage au Gabon et sur le Fleuve Ogooué."

PROF. KIEPERT, the eminent geographer, has recently expressed his opinion regarding the alleged return of the Amu Darya (or Oxus) into its ancient bed, and consequently becoming a tributary to the Caspian instead of the Aral Sea. The Professor remarks that all statements made hitherto, even as far back as those of the old Roman writers, are simple speculations, proving nothing else but merely the existence of a dry river-bed in the direction indicated. He thinks it a matter of course that, in the event of unusual accumulation of water in the Oxus, this bed may be filled with water for many miles' distance, and, during the few centuries for which we possess reliable data this event has happened so often, that the present recurrence need not in any way have given rise to so much talk and discussion.

MR. E. F. IM THURN, of the British Guiana Museum, paid a visit, in October and November last, to the Kaieteur Fall of the Potaro River, for the purpose of testing whether it was rightly described by its discoverer,

Mr. Barrington Brown, as "one of the grandest falls in the world," as well as to prove the truth of his (Mr. im Thurn's) idea that such a place ought to be a rich treasure-ground for a collecting naturalist. He professes to be disappointed with the fall because it is neither so high as the Yosemité Fall nor so broad as Niagara. But he visited it when the water was at its lowest volume, and yet, when looking at it from above, he confesses that the fall is one of "splendid and awful splendid beauty." Altogether we infer that Mr. Brown's description is essentially correct, especially when the river is at its fullest. The country on the road to and about the fall is described as of matchless beauty, and evidently it is a splendid field for a naturalist. The fall can be reached with comparative ease in a few days from Bartica Grove.

AT the November meeting of the Russian Geographical Society, Admiral Krusenstern described the results of his journey to Siberia in 1876 to investigate the possibility of connecting the basin of the Petchora with that of the Ob, and thus open a continuous water-way from Europe to Siberia. He reports favourably on the practicability of the scheme. The scientific results of the journey are topographical surveys, levellings of the principal parts of the route, a whole series of astronomical determinations, and a large addition to our knowledge of a region still little known.

THE last number of the Zeitschrift of the Berlin Geographical Society contains an elaborate paper by Herr G. Hartung on the formation of valleys and lakes. There is also a valuable paper by the late Saharan explorer, Erwin von Bary, on the character of the vegetation of Aïr; besides a large map of the African river Quanga, the result of the exploration of Herr Otto Schütt. The last two numbers of the Verhandlungen of the same Society contain some important papers. Prof. Karsten gives some data on the problem of ocean currents, and Dr. Tietze describes the results of his exploration of the volcanic Mount Demavend, to which we referred in a previous number. Dr. Hartmann has some interesting observations on the distribution of deep-sea animals. It will thus be seen that this Society regards geography as embracing a very wide field of research, and in this respect is a model that might with advantage be followed by other geographical societies.

A COMMITTEE has been formed at Berlin with the object of founding a "Central Union for Commercial Geography and the Furtherance of German Interests in Foreign Countries." The Society hopes to enter into friendly relations with all German and foreign geographical societies.

"BOSNIEN in Bild und Wort," is the title of an interesting work by Amand von Schweiger Lerchenfeld, just published by Hartleben, of Vienna. The geographical publications of this firm are of particular excellence, and the present work is a fair case in point. It contains some twenty charming drawings from the artistic pen of J. J. Kirchner, illustrating the most interesting parts of the province which has played so prominent a part in the past year's history. The text is carefully written, clear, and to the point. Altogether the work is an acceptable addition to geographical literature.

THE MARQUESS OF TWEEDDALE, P.Z.S. T is with extreme regret that we have to chronicle the three days' attack of bronchitis, on the morning of December 29, of Arthur Hay, ninth Marquess of Tweeddale, F.R.S., and President of the Zoological Society of London. Born in 1824, the second son of Field-Marshal the late Lord Tweeddale, K.T., a veteran of the Peninsula and other campaigns of "the Great War," Lord Arthur Hay at an early age entered the army, as befitted the godchild of the grand English

captain, and obtained a commission in the Grenadier Guards. But the ordinary guardsman's life in times of peace was inadequate to his aspirations, and reaching the rank of captain, he was soon after appointed aide-de-camp to Sir Henry (afterwards Lord) Hardinge, then GovernorGeneral of India, and in that capacity accompanied his chief through the ever-memorable campaign of the Sutlej. After the English arms had triumphed in the conquest of the Punjab, Lord Arthur was attached to a mission, the details of which, we believe, have never been made public, to some of the tribes bordering upon our northern frontier, and in discharge of that duty reached places unvisited by any European traveller since the days of Moorcroft. Lord Arthur's services in India and the adjacent countries lasted over several years, in the course of which time his attention was attracted by their rich and little-known fauna, and he not only formed the acquaintance, but assiduously cultivated the friendship of two of the greatest Indian zoologists of the time-Jerdon and Blyth-of whom he became an apt pupil, fishes and birds being particularly the objects of his pursuit. Returning home at length he resumed his regimental duties, and on the outbreak of the Russian war, in 1854, he accompanied the expeditionary force first to Turkey and thence to the Crimea, taking part in the operations which ended in the fall of Sebastopol. Soon after the conclusion of peace he left the army, and his old zoological tastes, which had been growing slack, returned to him more strongly than ever. On the death of his eldest brother, Lord Gifford, he became heir to his father's honours and estates, and assumed the courtesy title of Lord Walden, by which, perhaps, he will be most generally recognised, for under that designation he published the greater part of his contributions to zoology, and under it he succeeded the late Sir George Clerk as President of the Zoological Society, performing the duties of that office with a singular amount of dignity and urbanity. For several years he continued to live in a cottage he had built for himself at Chislehurst, and there he began to form an ornithological library and collection on a scale almost unattempted hitherto in this country, though the collection was supposed to be limited to Indian, or at least Asiatic, specimens. On the death of his father, at a very advanced age, in 1876, Lord Walden inherited the Scottish peerage and estates, and thenceforth his home was mainly the old ancestral seat of Yester, near Haddington, where he entered, with the energy natural to his character, upon the life of an agriculturist; in this respect following the example of his father, who had long since turned his sword into a ploughshare, and had earned the reputation of being one of the most scientific farmers in that part of North Britain, which is the headquarters of scientific farming.

The late Lord Tweeddale was a frequent and, when occasion required, a powerful writer. Most of his acknowledged communications are to be found in the Journal of the Asiatic Society of Bengal, the Ibis, and the Proceedings and Transactions of the Zoological Society, but it is believed that his anonymous contributions to the public press were still more numerous, though these were seldom on scientific topics. married twice: first, the daughter of the late Count Kielmansegge, for many years the popular Minister of Hanover at this Court, who died in 1871, and secondly, a daughter of Mr. Mackenzie of Seaforth, who survives him.

He

NOTES

We are happy to state that at the end of the last legislative session the French Central Bureau of Meteorology obtained from the National Exchequer a sum of 120,000 francs, required for the organisation of the services which were decreed in the month of June. A semi-monthly paper will be issued by the Bureau summarising the results of observations during that period. The work of normal schools, which had been suspended during two or three years, will be resumed and published

as in former times.

THE French Minister of Public Works has prepared a most important decree, which was signed on December 20 last. For the execution of the great works which have been voted by the French Parliament, an auxiliary corps of Ponts-et-Chaussées engineers has been created. The members of this newly created body will enjoy the same privileges as the government engineers who have been trained at the Polytechnic School. The consequence is that the privileges of that celebrated establishment are practically at an end, and the principle that office should be given to the fittest irrespective of their origin has a fair chance of becoming an axiom of the French administration.

THE first part of a posthumous work by Prof. Poggendorf on the History of Physics has been sent us by Messrs. Williams and Norgate. It will be completed in three parts and will contain much interesting matter collected by the late eminent physicist during his long career as lecturer at the Berlin University. We have also received the first part of the "Publications of the Astrophysical Observatory of Potsdam," containing observations of sun-spots from October, 1871, to December, 1873, by Dr. Spörer.

FROM Science Neros we learn that Mr. Alex. Agassiz left Cambridge (U.S.) on December I for a second dredging-trip in the West Indies on the Coast Survey steamer Blake. The specimens sccured by him are divided among scientific men in Europe and America, who work them up, while many of them go into his own Cambridge collection. This year he will cruise between the Windward Islands and the coast of South America, having spent last winter in the Gulf of Mexico.

THE prominence given to science is a noteworthy feature in the annual summaries for the past year which appear in most of our newspapers.

We have much pleasure in drawing our readers' attention to the following circular concerning a Society for the Collection of South African Folk Lore. The circular explains itself, and we trust that those of our readers who are interested in the subject will subscribe to the periodical which it is desired to start :"The existence, among the aboriginal nations of South Africa, of a very extensive traditionary literature, is a well-known fact. Not a few stories forming part of this literature have been written down; and as in some of them terms occur which no longer appear to be used in colloquial language, and the meanings of which are, in many instances, not fully understood, there is no doubt that we meet in them with literary productions of great antiquity, handed down to the present generation in a somewhat similar manner to that in which the Homeric poems reached the age of Pisistratus. But European civilisation is gaining ground among the natives, and within a few years the opportunities for collecting South African folk-lore will be, if not altogether lost, at least far less frequent than they are now. This would be a great loss to 'the science of man,' particularly as there is much which is exceptionally primitive in the languages and ideas of the South African aboriginal races. There are not a few missionaries and other Europeans in South Africa who have ample opportunities for collecting South African folk-lore. Some of