A glance at the above tables will show that the kind of variability presented by these objects is a very special one, and is remarkable for its great range. The light may be stated in themost general terms to vary about six magnitudes, from the sixth to the twelfth. This I think is a fair average; the small number of cases with a smaller variation I shall refer to afterwards. A variation of six magnitudes means roughly that the variable at its maximum is somewhere about 250 times brighter than at its minimum.1

I have already indicated that, with regard to the various origins of the variability of stars which have been suggested, those which have been always most in vogue consider the maximum luminosity of the star as the normal one; and indeed with regard to the Algol type of stars of short periods, which obviously are not here in question, there can be no reasonable doubt, that the eclipse explanation is a valid one; but in cases such as we are now considering, when we may say that the ordinary period is a year, this, explanation is as much out of place on account of period, as are such suggested causes as stellar rotation and varying amount of spotted area on a stellar surface, on account of range.

We are driven, then, to consider a condition of things in which the minimum represents the constant condition, and the maximum a condition imposed by some cause which produces an excess of light; so far as I know the only explanation on such a basis as this that has been previously offered is the one we owe to Newton, who suggested such stellar variability as that we are now considering was due to conflagrations brought about at the maximum by the appulse of comets.

I obtained by the formula I = (2':12)”. Lm + n' For differences of 5, 6, 7 and 8 mag, we get

Lm

= 100'02. Lm+5

=251 24.

Lm+6

=631'11. Lm+7

=1585 35. Lm + 8

=

=

light of a star of magnitude m.

magnitudes fain:er

How the Difficulty of Regular Variability on Newton's View is got over in mine.

It will have been noticed that the suggestion put forward by myself is obviously very near akin to the one put forward by Newton, and no doubt his would have been more thoroughly considered than it has been hitherto, if for a moment the true nature of the special class of bodies we are now considering had been en évidence. We know that at their minimum they put on a special appearance of their own in that haziness to which I have before referred as having been observed by Mr. Hind. My researches show that they are probably nebulous, if indeed they are not all of them planetary nebulæ in a further stage of condensation, and such a disturbance as the one I have suggested would be certain to be competent to increase the luminous radiations of such a congeries to the extent indicated.

Some writers have objected to Newton's hypothesis on the ground that such a conflagration as he pictured could not occur periodically, but this objection I imagine chiefly depended upon the idea that the conflagration brought about by one impact of this kind would be quite sufficient to destroy one or both bodies, and thus put an end to any possibilities of rhythmically recurrent action. It was understood that the body conflagrated was solid like our earth. However valid this objection might be as urged against Newton's view, it cannot apply to mine, because in such a swarm as I have suggested, an increase of light to the extent required might easily be produced by the incandescence of a few hundred tons of meteorites.

I have already referred to the fact that the initial species of the stars we are now considering have spectra almost cometary, and this leads us to the view that we may have among them in some cases swarms with double nucleiincipient double stars, a smaller swarm revolving round the larger condensation, or rather round their common centre of gravity. In such a condition of things as this, it is obvious that, as before stated, in the swarms having a mean condensation this action is the more likely to take place, for the reason that the more the outliers of the major swarm are drawn in, the more likely is the orbit of the smaller one to pass clear. The tables show that this view is entirely consistent with the facts observed, for the greater number of instances of variability occur in the case of those stars in which, on other grounds, mean spacing seems probable.

The Cases of Small Range.

So far, to account for the greatest difference in luminosity at periastron passage, we have supposed the minor swarm to be only involved in the larger one during a part of its revolution, but we can easily conceive a condition of things in which its orbit is so nearly circular that it is almost entirely involved in the larger swarm. Under these conditions, collisions would occur in every part of the orbit, and they would only be more numerous at the periastron in the more condensed central part of the swarm, and it is to this that I ascribe the origin of the phenomena in those objects-a very small number-in which the variation of light is very far below the normal range, one or two magnitudes instead of six or seven. Of course, if we imagine two subsidiary swarms, the kind of variability displayed by such objects as B Lyræ is easily explained.

NATURAL SCIENCE IN JAPAN. WITH the close of our eventful Jubilee year there was completed the first volume of a new journal of science which is destined to play a very important part in the advance of knowledge. We refer to the Journal of the College of Science of the Imperial University of Japan, already noted in these pages.

This periodical is issued under the joint editorship of four professors in the College whence it originated. These gentlemen, one only of whom is an Englishman, constitute a publishing committee: they have adopted the wise plan of issuing all communications on all subjects recognized within the one cover, and under their supervision there have already appeared a series of original papers of considerable interest, so far at least as those biological are concerned. The work is being well done: authors,

editors, publishers, and craftsmen appear to be working harmoniously in the production of a journal which, while it reflects the utmost credit on all, leaves nothing to be desired. Twenty-one original monographs have been set up, three of them in German, the rest in English. Of these five are biological, while six are devoted to physics, four to chemistry, three to seismology, and two to geology proper. It is to the first-named that we wish now to refer. The first paper published deals with the life-history of a parasite (Ugimya sericaria) which works fearful havoc among the silkworms in Japan: this monograph is in itself interesting, apart from its intrinsic merit, as showing that our Eastern friends are fully alive to the so-called practical application of their work. This and other valuable papers which we might name testify most satisfactorily to the thoroughness of, at any rate, one side of the undertaking; others there are which show that

these investigators are fully prepared to face some of the most formidable problems now exercising the mind of the zoologist, and in dealing with such problems they display a diligent attention and cautious generalization, such as are occasionally looked for in vain in writings nearer home. If this excellent beginning is, in these respects, indicative of that which is to follow, only results of the greatest value can ensue.

Of the zoological communications two are exceptional-we refer to those contributed by Prof. K. Mitsukuri, of the Imperial University, Tokio. One of these, on the germinal layers in Chelonia (produced in conjunction with his assistant, Ishikawa), has previously appeared in our own Journal of Microscopical Science. The other is deserving of especial comment, for it brings tidings of the establishment of a marine biological station of the Imperial University, at Misaki.

Misaki is a fishing settlement to the west of the Bay of Tokio, easily accessible, we are told, from Tokio or Yokohama in a day. Its waters have a direct interest for Western zoologists, in the fact that they have given birth to most of those museum specimens of Hyalonema, with which the skilful Japanese so long duped the rest of the world. Geographically, the relations of Japan to Asia may be appropriately compared with those of Britain to Europe in their greater climatic variations, however, the Easterns have an advantage, if only by way of variety in the fauna and flora thereby induced. Again, Misaki, says Prof. Mitsukuri, has "long been a favourite collecting ground for naturalists; almost every group of animals is represented in this region in more or less abundance," and he gives it as his opinion that zoologists have by no means "become acquainted with even a small part of all the interesting animals to be found." When we reflect

upon this, mindful of the climatic features of the district, | and in view of the enumeration given of known inhabitants of its waters, great expectations are conjured up, and the importance of the enterprise upon which our friends have embarked becomes self-evident.

The station has been founded by the Department of Education and the authorities of the Imperial University, as a special adjunct to the biological laboratories of the latter. As it is fair to assume that the governmental body will, like all others, expect "something practical" for its money, we anticipate that attention will early be given to questions of economic importance. The Japanese have a fishing population of more than 1,500,000 active workers, while it is computed that 36,000,000 persons, in all, are more or less dependent upon fish as food. When, in view of the total area and population of our own islands as compared with those of Japan, it is remembered that our own fishing population numbers little over 540,000, it becomes needless to point out that the Japanese are par excellence a fishing folk. They moreover appear to possess an ancient but limited literature on the subject.

The establishment, by the Japanese, of this and other similar institutions has been necessitated by the adoption of the products of Western civilization, almost, it would seem, in return for that "devout and learned admiration " so long accorded them by the Western nations. Rapid indeed has been their progress under influences which are bringing their wares into open competition with Western markets, and who shall say but that we proud Europeans may not yet be, perforce, to no small extent dependent upon them for edible produce?

The founding of this marine station is, biologically, a sign of the times. More than this, however. It is a mo ement upon which, in the long run, the intellectual as well as the commercial prosperity of a large section of the community must depend; for in the spread of that true science which seeks to unravel the knowledge of causes, there now lies the only sound basis for national prosperity. Prof. Mitsukuri's association with the undertaking is, in itself, a guarantee that these interests will be upheld. His earlier work was executed under the guidance of, and in fellowship with, American subjects whose names will be for ever memorable in the history of marine zoology: his association with them and with the illustrious Balfour, and his acknowledged indebtedness to Dohrn, are, in themselves, auguries of success. We note with much satisfaction that "arrangements will be made by which students in the biological course of the University will be required to pass at least one term in the station": workers will be thus assured, and we tender them our sincere congratulations and hearty good wishes for a prosperous development of their enterprise. must not be forgotten that the Japanese waters have lately yielded us the interesting Chlamydoselache, and it would be a most interesting circumstance should the farfamed Hyalonema, to which Prof. Mitsukuri so frequently reverts in his article quoted, receive final consideration at the hands of his countrymen.

It

The following is a brief description of the station itself, extracted from the original article. "The building is of plain wood, and one story high, except in the middle part, which has a second floor. The main laboratory-room (A), which occupies the whole sea-front, is 48 feet long, 12 feet wide at the two ends, and 18 feet in the middle, and is able to accommodate about ten workers. A number of small aquaria for the use of investigators will be placed in this room. Of the rooms at the back of the main laboratory, one (B) has a cement floor and is for assorting and preserving specimens brought in from the sea. Another (E) is to be used as the library-room, and a third (C) as the store-room. The second floor over the central part of the building is able to give sleeping accommodation for a few persons. From a tank placed outside the

building, fresh sea-water is carried into the main labo:atory-room and the assorting-room, and is delivered out of many facets." G. B. H.

THE AURORA IN SPITZBERGEN1

THE best observations hitherto made on the aurora borealis are those made at Bossekop, by Bravais, during the expedition of the French corvette Le Recherche, 1838-40. Bossekop is also situated in the maximum zone of the auroras, on the coast of Northern Norway. Considering that Spitzbergen lies a little north of the same zone, and nearly on the same meridian as Bossekop, it was resolved that the observations of auroras should be made with the greatest possible care at the Swedish International Polar Station at Spitzbergen in 1882-83. This work was confided to Mr. Carlheim-Gyllenskiöld, and the auroral observations are the most complete that have been made by any of the international expeditions during that year.

The results are now printed, and form a large quarto volume of 409 pages, with a great number of tables, illustrations, and figures. The results confirm and enlarge those of Bravais, and of other observers of this brilliant phenomenon.

(1) The first question is the determination of the mean co-ordinates of the auroral arch. A mean of 371 measurements gave the azimuth of the culminating point or summit of the auroral arch in S. 24° 12′ E. As early as 1834, Argelander, in Åbo, Finland, found that the azimuth of the culminating point of the auroral arch differs about 10° from the magnetic meridian. At Bossekop the magnetic declination was N. 10° 8' W., and the declination of the culminating point of the auroral arch N. 22° 4′ W., the anomaly being, of course, about 11° W. The magnetic declination at Cape Thordsen was found to be N. 12° 45′ W., and of course the auroral anomaly from the magnetic meridian was 11° 27′ W.

(2) Eighty-seven measures on the position of the corona borealis were made, and the position of the centre of the corona was found nearly in the magnetic zenith, and not in the same vertical as the highest point of the arch. The means are :—

H Position of the magnetic zenith H Position of the culminating

H =

Az. = S. 24 12 E.

point of the arch This confirms the measurements made during the past century by Wilcke, Mairan, and others.

(3) The breadth of the auroral arches varies with their elevation above the horizon. The arches consist of rays running in the direction of the breadth of the arch, and converging towards the magnetic zenith. Thus they form pended, like a curtain, from east to west, but with a small a long fringe of rays parallel to the dipping-needle, sus

extent of breadth from north to south. If this curtain of rays moves from the horizon to the zenith, the breadth gives the greatest breadth at a height of 45°. In the varies according to the laws of perspective. The formula neighbourhood of the zenith the arches are very narrow, stretching as a luminous band across the heavens.

(4) Besides the arches and rays, the auroral light somesurface, thus floating in space as a horizontal layer of light, times formed a true spherical zone parallel with the earth's often crossed by several arches. This form is seldom to be seen in lower latitudes. These auroral zones were apparently much broader in the zenith than at their extremities nearer to the horizon. When such an auroral zone was lying wholly over the heavens, with the excep

1 "Observations faites au Cap Thordsen, Spitzberg, par l'Expédition Suédoise." Tome II. (1) Aurores boréales. Par Carlheim-Gyllenskiöld.

tion of a low segment near the horizon, a dark segment was produced by contrast. Sometimes the luminous zone was broken, and then dark spots or irregular spaces were produced in the same way. These dark spaces were frequently seen tinted with a faint rosy light.

(5) The movement of the arches is ordinarily reported to be from north to south, at places situated to the south of the maximum zone, and, from the opposite direction, at places within the maximum zone. Thus, at different stations between the latitude of Rome and the latitude of Bossekop, 69.6 per cent. of the auroral arches have moved from the north; at Mossel Bay, Franz-Josef Land, and Discovery Bay, on the contrary, 62:5 per cent. have moved from the south. At Cape Thordsen it was of course expected that the most part of the auroral arches would move from the south. Yet this was not the case. On the contrary, 57'6 per cent. moved from the north. The movements were, of course, almost the same in both directions.

(6) The anomalous forms of arches were very frequent, and were made a matter of accurate investigation. Sometimes an auroral arch presents the form of a sinuous band, or resembles a brilliant curtain with deep folds. At other times the arches appeared as regular spirals. Seen from the outside of the earth, or from above, the spirals were almost all contorted in a direction contrary to the motion of the hands of a watch, and the undulations folded as an S. The motion was, in 80 per cent., from west to east. The folds of the auroral draperies had very different dimensions on different occasions. Sometimes a regular arch showed only a slight undulation; at other times, only a part of an immense auroral drapery was seen above the horizon, as a pseudo-arch.

(7) Often, waves of light are running along the arches, and then the rays or beams are apparently in vivid motion. This appearance of the aurora is known in England as "the merry dancers." In 103 cases the waves were running from west to east, and in 101 cases from east to west. The mean angular velocity per second was 386. For a mean vertical height of the aurora of 100 kilometres above the earth's surface, or 222 kilometres from the observer's eye, this gives the immense velocity of about 25 kilometres per second. The light of the aurora was often suddenly changing as to the distribution and intensity of light, but the geometrical form of the whole phenomenon was only slowly varying. The rays were sometimes observed to have a slow proper motion from west to east, or vice versâ.

(8) As to the classification of the auroral forms, the author rejects that of Weyprecht. The different forms of the aurora in the classification of Weyprecht are, in fact, only different views or projections, as, for instance, the forms III. = beams or rays, and IV. = corona. The corona results, according to the rules of perspective, when a large number of separate beams parallel to each other and to the direction of the dipping-needle seem to converge to one point, viz. the magnetic zenith. A regular and fully-developed arch consists, as we have said before, of a long fringe of rays, and so on. The author considers only two different forms of auroral light, viz. zones, or horizontal layers of light; and arches, composed more or less of distinct rays parallel to the dipping-needle. The arches present themselves in four different conditions: (1) arch, or a regular band; (2) band, or drapery; (3) spiral; and (4) pseudo-arch.

(9) The light of the aurora is, according to the author, of two kinds: (1) the yellow light, entirely monochromatic, and showing in the spectroscope the well-known yellow line of Angström; (2) the crimson or violet light, resolved in the spectroscope into several rays and bands, spread over all parts of the spectrum. In the following table we give (I.) the lines observed by the author, (II.) the lines observed by several authors before the year 1884, and (III.) the spectrum of lightning, according to the observations of Herschel, Vogel, Schuster, and the

There were twelve other extremely faint auroral rays to be seen occasionally, but their position could not be exactly observed.

As to the further discussion of the different auroral spectra and their supposed connection with different auroral forms, we must refer to the original paper.

(10) No sound was ever heard from the auroral light. The feeble rustling noise sometimes heard was observed to come from the loose agile surface-layer of snow driven to and fro by the lightest wind over the underlying layers. Nor was a smell of sulphur " observed.

(11) As to the height of the aurora, it may first be mentioned that the aurora was never seen to descend below the mountains or the lower clouds. Only two or three times it is possible that the light was seen below the upper clouds. Yet sometimes the auroral light was seen to be reflected from the surface of the snow. Direct measures of the parallax from the end of a short base (573 metres), by means of auroral theodolites of Mohn's construction, gave an average height of 551 kilometres; from observations of the corresponding amplitudes and heights of the arches, according to Bravais' method, 57'7 kilometres; and by several other observations and calculations, about 60 kilometres was found to be the probable mean height of the aurora.

(12) As to the annual and diurnal periods of the aurora, no annual variation in the frequency could be proved. The apparent daily period gave a maximum at 8h. 50m. Göttingen time, or 9h. 13m. local time, in the evening; and a minimum at exactly the same hour in the morning. This apparent period must be corrected for the influence of the quantity of clouds and for the influence of the twilight. If F represents the apparent frequency of the aurora, and Q the quantity of clouds in tenth parts of the whole sky, there was found F = I 0'0730 Q, in taking for unity the apparent frequency when the heavens were totally clear.

Further, the apparent frequency when the sun was 10° 47' below the horizon was the half of the true frequency, and the influence of the sun's light was sensible as far as to a depth of the sun of 17° 45' below the horiOnce only the aurora was seen when the sun was not more than 5° 25′ below the horizon.

zon.

Taking into account these sources of error, the true daily range has a maximum at 3h. 3m. p.m., and a minimum at 8h. 3m. a.m. local time.

Finally, there was also a well-marked daily range in the form of the aurora. The most brilliant phase of the phenomenon occurred at 4h. p.m.; the aurora then apOn the other hand, peared as a complete regular arch. the minimum brilliancy took place at 9h. a.m.; the arches then were resolved into whirling fragments. Upsala, April. H. HILDEBRANDSSON.

NOTES.

THE general arrangements for the Bath meeting of the British Association have now been made. The first meeting will be held on Wednesday, September 5, at 8 p.m. precisely, when

Sir H. E. Roscoe will resign the chair, and Sir F. J. Bramwell, President-elect, will assume the Presidency, and deliver an address. On Thursday evening, September 6, at 8 p.m., there will be a soirée; on Friday evening, September 7, at 8.30 p.m., a discourse on "The Electrical Transmission of Power," by Prof. W. E. Ayrton; on Monday evening, September 10, at 8.30 p.m., a discourse on "The Foundation Stones of the Earth's Crust," by Prof. T. G. Bonney; on Tuesday evening, September 11, at 8 p.m., a soirée. On Wednesday evening, September 12, the concluding general meeting will be held at 2.30 p.m. Excursions to places of interest in the neighbourhood of Bath will be made on the afternoon of Saturday, September 8, and on Thursday, September 13.

THE fourth session of the International Geological Congress will be opened on Monday evening, September 17, and will last during the whole of the week. The meetings will be held in the rooms of the University of London, Burlington Gardens. The Honorary President of the Congress will be Prof. Huxley; the President, Prof. Prestwich; the Vice-Presidents, the Director-General of the Geological Survey, the President of the Geological Society, and Prof. McK. Hughes; Treasurer, Mr. F. W. Rudler; and General Secretaries, Mr. J. W. Hulke and Mr. W. Topley. Up to the present date 395 geologists have signified their intention of being present. Of these 210 are British, and 185 foreign. The number of countries represented

is 22.

THE Linnean Society holds its centenary celebration to-day. The following is the programme of the proceedings :- At 2.30 p.m. the President will receive the visitors. At 3 p.m. the President will take the chair. After introductory remarks by the President, and the formal business of the anniversary meeting, the Treasurer will lay before the meeting an account of the financial condition of the Society during the last century; the Secretaries will lay before the meeting a history of the Linnean books, herbarium, and other collections; the President will deliver the annual address. The following Eulogia will be pronounced: On Linnæus, by Prof. Thöre Fries, the present occupant of the Chair of Botany at Upsala; on Robert Brown, by Sir Joseph Hooker; on Charles Darwin, by Prof. Flower; on George Bentham, by Mr. W. T. Thiselton Dyer. The Linnean Gold Medal, instituted by the Society on the occasion of its centenary, will be presented to Sir Joseph Hooker (botanist), and Sir Richard Owen (zoologist). (In subsequent years the presentation will be alternately to a botanist and zoologist.) At 6.30 p.m. the annual dinner will be held at the Hotel Victoria, Northumberland Avenue, the President in the chair. morrow (May 25th), at 8.30 p.m., the President and Officers will hold a reception of the members and visitors in the Rooms of the Society, when the Linnean collections and relics will be exhibited.

To

THE late Mr. Cooper Foster, of Grosvenor Street, for many years senior surgeon to Guy's Hospital, was famous among horticulturists as a collector and grower of Hymenophyllums, Trichomanes, and Todias, popularly known as Filmy Ferns. With very few exceptions, the whole of these plants are extremely difficult to cultivate. The conditions under which they grow naturally are not easily imitated. Mr. Foster, however, contrived to keep a very rich collection of species, many of them unknown in gardens except at Kew, where the collection of Filmy Ferns is perhaps unique; and even Kew did not possess several kinds which Mr. Foster possessed. When it is remembered that these extremely delicate plants were cultivated in one or two small greenhouses at the back of a house in Grosvenor Street, Mr. Foster's success appears still more remarkable. After his death the Filmy Ferns were removed to his son's residence at Binfield, Berks. Recently, however, Mrs. Foster offered the whole

collection to Kew, and it has lately been transferred to these Gardens, special accommodation having been provided for it in the house (No. 3) where the bulk of the Kew collection is grown. Among the most noteworthy of the plants comprised in the Cooper Foster collection are Trichomanes reniforme, a magnificent specimen a yard across, bearing hundreds of fine healthy leaves; T. parvulum, which has a compact cushion-like mass of tiny palmate leaves; T. alabamense, Hymenophyllum aruginosum, H. chiloense, H. eruentum, H. flexuosum, H. Fosterianum, H. pectinatum, H. pulcherrimum, and some grand masses of H. demissum. This magnificent gift to the national gardens at Kew will no doubt receive the appreciation from the public which its intrinsic beauty, scientific interest, and actual pecuniary value deserve.

MRS. EMMA W. HAYDEN has given to the Academy of Natural Sciences of Philadelphia in trust the sum of $2500.00, to be known as the Hayden Memorial Geological Fund, in commemoration of her husband, the late Prof. Ferdinand V. Hayden. According to the terms of the trust, a bronze medal and the balance of the interest arising from the fund are to be awarded annually for the best publication, exploration, discovery, or research in the sciences of geology and palæontology, or in such particular branches thereof as may be designated. The award and all matters connected therewith are to be determined by a Committee, to be selected in an appropriate manner by the Academy. The recognition is not to be confined to American naturalists.

ACCORDING to the Colonies and India, the appointment of Superintendent of the Botanical Gardens, Singapore, has become vacant owing to the death of Mr. Cautley in Tasmania.

M. HERVÉ MANGON, Member of the Paris Academy of Sciences, and President of the French Meteorological Councils died on the 16th inst., at the age of sixty-seven. He was Minister of Agriculture in the Brisson Cabinet, and was a high authority on drainage and agricultural improvements.

THE Pilot Chart of the North Atlantic Ocean for May show, that, generally, fine weather prevailed over that ocean during April. Storms accompanied by electric phenomena occurred about once a week north of the 40th parallel. A cyclonic storm of great strength was generated on April 15 in about 35° N. and 60° W., moving across the Banks from the 16th to the 18th, in which the wind reached force 11. There was also a gale of considerable strength to the north-eastward of the Azores during the second week of April, and a "norther" was felt in the western part of the Gulf of Mexico on the 13th. Considerable fog was met with off the Grand Banks, and southwards. The amount of ice encountered was unusually small, and was confined for the most part to the south-east coast of Newfoundland. Although it has been delayed in its southward movement by the unusual prevalence of south-easterly winds, it is now liable to appear in quantity, and to constitute a source of danger for several months. Careful observations of the Gulf Stream and the equatorial current are now being made at certain points by the United States steamer Blake.

A SODIUM salt of zincic acid has at last been obtained in the crystalline state by Messrs. Comey and Loring Jackson, of Harvard University (Berichte, 1888, 1589). Every analyst is aware that zinc hydrate is soluble in potash or soda, and although it has been presumed that zincates of the alkalies or compounds of the alkaline oxides with zinc oxide are formed under these circumstances by replacement of the hydrogen of the hydrate by potassium or sodium, no such compounds have hitherto been isolated. Messrs. Comey and Jackson, however, find that when a concentrated solution of zinc or zinc oxide in soda is shaken with alcohol the mixture separates on standing into two layers