between the different sections and individual papers, the unity of the whole would have been such as to make the four volumes of the Arbeiten an excellent special treatise on physical chemistry.

Although this would undoubtedly have increased the value of the work to outsiders, it is perhaps rather antagonistic to its raison d'être, since it is primarily the collected published papers from the physico-chemical laboratory of the University of Leipzig. As such it is not only a welcome souvenir to those who have worked in the old laboratory, but it should be in the hands of all who are interested in physical chemistry. JOHN SHIELDS.

To deal with the above-named publications in inverse order, it may be remarked that Dr. Wolfenden's treatise of fifteen quarto plates and six pages of letterpress is the outcome of the radiography, by means of a 10-inch spark-coil, of a collection of Echinodermata dredged in the Orkney Seas during 1896-97. The author claims that it has been his endeavour "to show that the new method of radiography may be made of considerable service in zoology, as an accessory to dissection and description." The plates are mostly inartistic and of no practical value to the zoologist-at best but poor examples of the radiographer's art. While they betoken a laudable desire on their originator's part to develop the new light of physical science, they partake of the nature of mere experimental memoranda such as are usually made a basis for fuller investigation and allowed to pass unpublished.

Of the Archives it may be noted that with the number under review the title is changed from that "of Skiagraphy" to that "of the Roentgen Ray." The seventeen pages before us are chiefly conspicuous as containing a full report of the inaugural meeting of the Röntgen Society of London, a combination of a conversazione, a trade exhibit, and a concert, set around a presidential address. The latter, reported in extenso, deals with the history, development, and application of the Röntgen discovery, to the invoking of Shakespeare. Special stress is laid upon the advantages likely to accrue to the medical profession by the employment of the X-ray tube; and since the members of that profession seem likely to profit both by its use and its user, they ought for the future to be among its foremost advocates. It is thus but appropriate that the body of the Archives should be devoted to a brief description of five plates mainly illustrative of the osteological phenomena of "acromegaly”—which we would remark is now more correctly known as megalacria. Beyond this there are a few desultory notes of a practical order, but we are unable to detect anything which might not have been communicated in the customary form to one or other of the established scientific societies. We fail to see the justification for the foundation of a new society, and shudder at the assertion that there are already "three journals established for the publication of observations and discoveries connected with the Roentgen rays," not to say at the suggestion of rivalry in the wording of the cover of the issue under review. Concerning the zoological departure, however, a good purpose will have been served, in the awakening of the mind of the physicist to the fact that animals exist and have a form and symmetry capable of scientific treatment.

Practical Electricity and Magnetism. By John Henderson, B.Sc. (Edin.), A.I.E.E. Pp. xv + 388. (London : Longmans, Green, and Co., 1898.)

THIS little volume, the second of a series of laboratory manuals at present being brought out by Mr. Henderson in conjunction with Mr. Joyce, has certainly many points about it which are not only original, but which should also render it of the greatest value in the physical laboratory.

It is designed "to provide a course of instruction for carrying out a progressive series of experiments in electricity and magnetism," and, though it is written, not for technical students, but for students of science, one is nevertheless struck with the author's extremely high ideal of laboratory experimental work. The student receives at the outset a preliminary admonition which cannot be described as other than most excellent and to the point. He is assumed to have plenty of time at his disposal, and not to be engaged in getting through a certain set of experiments in a given time: conditions which can hardly be expected of students preparing themselves for any practical examination, or even in every case of students engaged in original research. The writer's effort to inculcate an almost impossible ideal is none the less a most praiseworthy feature of the book.

The descriptions of recent experimental work are well up to date, though perhaps such work has received here and there an almost undue prominence. At the end of each section, a list of references to original papers bearing on the subject is given. These lists, which are carefully prepared, will recommend the book to all who are engaged in looking up in detail any particular branch of the subject.

The notation used is not always happily chosen, as, for example, the double meaning of the letter Ron p. 108-9; and the book is by no means entirely devoid of unfortunate mistakes, as in the table on p. 378, where the mechanical equivalent of heat is given as 42400 grms. per "C" instead of " 42400 grm-cms. per °C." Such faults will, however, no doubt disappear in a second edition.

Much practical and detailed advice on the carrying out of experiments is given, which it would be hard to find in so concise a form elsewhere; and, though the manual is for this very reason not exactly readable, yet this portion of the work, together with the tables of references to original papers already alluded to, and the concluding set of numerical tables and physical constants, combine to make up a most useful work for the physical laboratory. D. K. M.

La photographie et l'étude des nuages. Par Jacques Boyer. 8vo. Pp. vi + 80. Twenty-one illustrations. (Paris C. Mendel, 1898.)

AT the International Meteorological Conference at Munich, in 1891, a Committee was formed to consider the question of concerted observations on the direction of motion and the height of clouds, and subsequently various countries were invited to undertake special observations during a year commencing May 1, 1896, a period which was afterwards extended until August 1897. A Committee was also appointed to prepare a Cloud Atlas, based on the classification of Dr. Hildebrandsson and the late Mr. R. Abercromby, and instructions for observing and measuring the altitudes of the clouds by theodolites and photogrammeters were prepared by experts in this branch of meteorological science. The present handy little volume is the outcome of this action, and brings into a small compass a considerable amount of useful information which is spread over various publications, some of which are not easily accessible. It is divided into four parts: (1) the history of the subject from the middle of the eighteenth century; (2) classification according to the atlas above referred to, with a number of

illustrations; (3) description of the photographic apparatus employed, and (4) the method of measuring the pictures obtained. The two last chapters will be very valuable for any one proposing to undertake the difficult task of photographing the clouds, and of determining their heights and movements. In referring to the various attempts at cloud classification, we do not find any mention of "Cloudland,” by the late Rev. W. C. Ley. Proceedings of the London Mathematical Society. Vol. xxviii. Demy 8vo, pp. 594. (London: Francis Hodgson, 1897.)

THIS collection of thirty-four original papers on every branch of mathematics affords abundant evidence that English mathematicians are not behindhand in moving with the times. If proof be needed that the younger generation of mathematicians are quite following in the lines of those that have gone before them, it may be sufficient to mention that at least six of the papers are by men who have graduated at Cambridge since the year 1886. As might be expected, "Partitions" and "Groups" occupy a prominent place, seven of the papers being devoted to them. The former of these two subjects is ably introduced by Major MacMahon, F.R.S., in his address on "Combinatory Analysis," delivered on retiring from the office of president; and the publication of the outlines of seven lectures on the "Partitions of Numbers," delivered by the late Prof. Sylvester at King's College, London, in 1859, is another important feature. On the other hand, "hyper-Euclidian geometry" is conspicuous by its absence, and applied mathematics is represented by eight papers only.

During the past year the London Mathematical Society has lost two members in addition to the late Prof. Sylvester: the Rev. Alexander Freeman, who died on June 12, 1897, and Lieut.-Colonel John Robert Campbell, who died on June 23. Colonel Campbell, besides serving on the Council, was a benefactor to the Society, and we understand that had it not been for his munificence it would have been impossible for the Society to issue such large and interesting volumes of Proceedings as the one now before us.

First Year of Scientific Knowledge. By Paul Bert. Translated by Madame Paul Bert. Revised and partly re-written by Richard Wormell, D.Sc., M.A.; and Montagu Lubbock, M.D. Pp. vi + 417. (London: Relfe Brothers, Ltd. Paris: Armand Colin and Co.) THIS is a revised edition of a work which has had a very successful career, but is constructed upon a plan which has little to commend it. The revision has consisted in bringing the information into line with current scientific knowledge, the plan of the book remaining as in the original. The rudiments of zoology, botany, geology, physics, chemistry, animal physiology, and vegetable physiology are all described in the four hundred pages which constitute the text, so that the book is comprehensive in its scope, if nothing else. The chief fault we have to find is that far too many technical terms are defined and used, so that the unfortunate pupils who are introduced to natural history by this book will be given the idea that science consists chiefly of words of Greek origin, and an unpronounceable terminology.

Who's Who, 1898. Edited by Douglas Sladen. Pp. xviii+846. (London: A. and C. Black, 1898.) THIS is undoubtedly the handiest biographical dictionary and compendium of information, referring to prominent persons and their doings, in existence. It contains nearly seven thousand biographies-mostly autobiographies-of the leading men and women of the day, and a large amount of information in addition. Among the general contents of interest to men of science is a list of Royal, National and learned societies, showing

the addresses of the societies, secretaries' names, annual subscriptions and other conditions of membership. We notice also a table of university degrees, with the correct explanation of each, a list of chairs and professors in the great universities of the United Kingdom, arranged alphabetically by their chairs, and a list of Fellows of the Royal Society (most of whom appear among the biographies). The volume is one to be kept on the writing table for ready reference; and it possesses the merit of including in its pages biographical details of more men of science than usually figure in similar reference books, though even now some of the minor literary lights could be struck out with advantage to make room for wellknown scientific men who have been omitted.

LETTERS TO THE EDITOR

[The Editor does not hold himself responsible for opinions expressed by his correspondents. Neither can he undertake to return, or to correspond with the writers of, rejected manuscripts intended for this or any other part of NATURE No notice is taken of anonymous communications.]

Mechanism of Self-fertilisation in the Banana,

I PROPOSE to describe here the mechanism of fertilisation in the banana plant.

(1) Packing of the inflorescence.-The inflorescence in this plant is packed air-tight in the large red-coloured bracts, whose margins are secured in place by a sort of cement. If we remove one of these bracts and examine the buds within, we find that the reproductive organs are also packed air-tight in the perianth. A closer examination of this packing is necessary to understand its efficiency.

The perianth consists of an outer whorl and an inner whorl ; the outer one consists of three sepals, usually united into an united together, only two are united and one is free, which in elongated concave hood. (Sometimes, instead of the three being the bud is partially overlapped by the other. Very rarely the three are quite free. In about fifty examples I examined, I

got only one flower with all the three sepals distinct.) The margins of the hood are folded inwards, so that they overlap each other. There is no fixed rule as to which is the outer, and which the inner, sepal. Sometimes the right overlaps the left, or vice versâ. This overlapping is not complete throughout their length, and cannot possibly be so. For, to ensure the packing being air-tight, the pectinate inflorescence must necessarily be concavo-convex, i.e. convex without and concave within; and obviously any cylindrical tube bent concavoconvexly must necessarily leave a gap or a window at the bottom (see Figs. 1 and 2).

This window would be a very weak point in the packing, and hence most accessible to insects or other injurious agencies if the outer packing became loose by accident. This weak

point must, therefore, be guarded first; and we see that nature has done it by closing the window with one of the petals of the inner whorl. This petal is convex in front and concave behind, while the hood is convex behind and concave in front. This arrangement shuts off the window completely (Fig. 3). The petaloid shutter is secured in its place, on either side, by the margins of the hood to nearly an eighth of an inch. These margins are very much thinned out, and are also cemented together. The shutter, being on the concave side of the bud, comes in contact with the convex bract beneath, which thus helps to keep it in position. The top of the hood is closed similarly air-tight by its margins. The inner whorl-i.e. the corolla-is represented usually by the shutter alone. Some times, however, two petals are present, and very rarely all the three.

The male organs, thus tightly packed, can neither move from their place, nor can they be assailed by any foreign element from without.

(2) Arrangement of the stamens.-On removing the hood and the shutter we come to the androecium, which consists of four or five stamens. The filaments are petaloid and erect, thus embracing the pistil completely. The anthers are adnate or dorsifixed. They are also introrse, i.e. turned towards the stigma.

Let us now proceed to the pistil, and examine it in the different stages of its growth. In the early state-i.e. before it is ripe, and before the anthers are ripe also-the style and

If this state conthe stigma project beyond the androecium. tinued, self-fertilisation would be impossible. The stamens must either overtake the stigma, or the stigma must be at the mercy of insects or the wind for pollination. The stamens are not quick enough in growth to overtake the stigma; so what happens is this. By the time the anthers are ripe, the style shortens in length by bending nearly at right angles in two places (often marked by horizontal grooves in early stages), and thus brings the stigma in contact with the pollen (see Figs. 4 and 5). After pollination is completed, the style straightens again and projects, as before, beyond the androecium (see Fig. 6). Stages intermediate between Figs. 4 and 5, may be seen if we examine the flowers from without inwards. With the straightening of the style, the anthers become free and curve outwards. The bracts fall off; the shutter drops away; the hood withers, and the style dries gradually. Kolhapur, India, February 17.

GOPAL R. TAMBE.

Stereoscopic Projection of Lantern Slides. IN your report of the meeting of the Physical Society on February 26 (NATURE, p. 454), I notice an account of the exhibition, by Prof. T. C. Porter, of a somewhat complicated apparatus for exhibiting lantern slides in stereoscopic relief. An equally elaborate arrangement, depending on the use of polarised light, was exhibited at the British Association at Nottingham in 1893. It may possibly, therefore, be of interest to call attention to the much simpler means of accomplishing the same result, which suggested itself to me some time ago,

but I subsequently found that it had been invented previously by Lieut.-Colonel Moëssard under the name of monocular stereoscope (Cosmos, May 23, 1896).

In this stereoscope one eye views one of the pictures directly, while the other eye sees the other picture after reflection at two mirrors, the angle between whose planes can be adjusted so as to bring the image into apparent coincidence with the picture seen by the first eye. In viewing distant pictures, such as lantern slides, a projecting partition, with a flange whose breadth is nearly equal to the distance between the two eyes, is all that is necessary to prevent either eye from seeing the wrong picture.

For lantern work, either two pictures could be projected side by side with separate lanterns, or two small views could be photographed side by side on the same slide, and thus enable stereoscopic effects to be shown with a single ordinary lantern.

Moreover, by turning the arrangement of mirrors through 90° it can be made to displace the image seen by one eye vertically instead of horizontally. This would enable the two pictures of an oblong view to be projected one above the other, instead of side by side, and viewed with the same apparatus as before, but differently arranged. As regards the foreshortening of the upper picture, this would be to a great extent compensated for by the fact that the lantern itself projected the picture upwards. It is evident that two pairs of mirrors, one for each eye, could be used if desirable. G. H. BRYAN.

The Aurora of March 15.

I WAS fortunate enough to witness the display of the aurora on the night of the 15th, and think that some of the appearances may be of interest to those who did not see them, but who have recorded the accompanying magnetic disturbances.

The display began in the north-east about eight o'clock, by the appearance of a brilliant band of light, rising from behind a cloud 45° from the horizon, and extending about 30° in a southwesterly direction. This band might have been mistaken for a search-light, the edges were so sharp. The colour was the characteristic greenish hue of the aurora.

After persisting steadily for five minutes the band gradually broadened and shortened, and became a bright patch, which continued until the end. The display spread over the northern sky to the west, where another patch appeared. At nine o'clock the display was very fine, with two patches east and west, and right overhead seemed to be the apex of a parabola with beams of light streaming northwards. Looking southwards, occasional flashes of a yellowish pink colour could be seen. About ten o'clock the whole energy of the display seemed to become concentrated in the east and west patches, and great flashes of light connecting the two. After this the brightness seemed to gradually diminish.

So bright was the aurora at its height that the grey granite walls of the houses were illumined by the flashes. Aberdeen, March 25. A. GEO. SMITH

On Phosphorescent Sap in Superior Plants. IN answer to the question of Prof. Giglioli in NATURE of March 3 (p. 412), I beg to observe that in Meyen's "System der Pflanzen-Physiologie," which was certainly in its time a standard work, there is to be found in vol. ii. p. 203 (Berlin, 1838) a short but concise statement of the phosphorescence of the milk-juice in Euphorbia phosphorea, on the authority of v. Martius ("Reise in Brasilien," ii. pp. 726 and 746), as also a reference to a communication by Mornay (Philosophical Transactions, vol. vi. p. 279), on the phosphorescence of the milk-juice" in einem rankenden Gewächse, Cipo de Cunanam genannt, welches zwischen Monte Santo und dem Flusse Bendego wuchs und wahrscheinlich eine Asclepiadee oder ein Apocynee ist." M. W. BEIJERINCK.

Delft, Holland.

A Remarkable Case of Correlation.

A VERY interesting case of correlation is recorded in the Bulletin of the Botanical Department, Jamaica, for December 1897.

Particular attention has been paid lately to the selection of good Ripley pine-apples, and it is found that if there is a broad red stripe in the centre of the leaf the fruit will turn out good; in other cases the fruit goes into holes at the bottom, and is attacked by ants. S. N. C.

WH

MRS. BISHOP'S KOREA.1

WHEN, after returning from the perils and hardships of her adventures in the Bakhtiari country of Persia, Mrs. Bishop announced her intention of making an extensive journey in Eastern Asia, her friends knew that she would not return without having something of interest to tell regarding her travels in little-known regions. Although unfortunately ignorant of the languages of the countries in which she was to travel, and therefore dependent on others to a large extent, Mrs. Bishop had most carefully prepared herself for making all necessary observations and records. She is particularly to be con

FIG. 1.-A Canyon in the Diamond Mountains.

gratulated on her skill as a photographer. The points of view were very carefully chosen, and the exposures accurately calculated, while the practice of developing the plates at the time, allowed duplicates to be taken if the first negative proved defective. The result is one of the best collections of photographs which we have seen as the result of a travelling amateur. We must congratulate the publishers also on the manner of reproduction employed the more important views are printed as separate "Korea and her Neighbours. A narrative of travel, with an account of the recent vicissitudes and present position of the country." By Mrs. Bishop (Isabella L. Bird), F.R G.S. With a preface by Sir Walter C. Hillier, K.C M.G., late H B. M.'s Consul-General for Krea. With maps and illustrations. 2 vols. (London: John Murray, 1898)

plates by the half-tone process, the others are reproduced as line-and-stipple blocks in the text, allowing the book to be printed on unglazed paper, and giving the volumes a lightness which is as desirable as it is rare.

Mrs. Bishop deals here with only a portion of her recent travels. Her important tour through Sze-chuan, on which she read a paper to the Royal Geographical Society-the first paper ever read by a lady to that Society-is not referred to, and the journey through Manchuria is but lightly touched on. Korea is the central theme; and although the interests of the authoress were obviously with the social and political aspects of the country rather than with its physical and biological con

ditions, she succeeds in giving an excellent general account, all the more valuable because not a little rubbish has been written by chance visitors at the treaty-ports. We may be pardoned if we feel a little regretful that-for example-the character of the interesting rock in the foreground of the photograph we reproduce (Fig. 1) is not described; but doubtless, the pioneer work having been accomplished, scientific travellers will follow, who can tell us whether the stone is merely water-worn or bears the sign-manual of ice.

We have one definite fault to find, and that is with the spelling of Russian placenames. Wladivostok is an incorrect transliteration. A German would write Wladiwostok properly enough; but the Russian letter B can only be represented by in English, and the usual form of the name Vladivostok is the only correct one. There are some other slips-such as Richofen for Richthofen, and the terms flora and denudation are applied in a popular rather than a scientific sense.

Mrs. Bishop describes her landing at Chemulpo, and the journey to Seoul by land; one could hardly say by road, for "traffic has worn for itself a track, often indefinite, but usually straggling over and sterilising a width enough for three or four highways, and often making a new departure to avoid deep mud-holes." A residence in the insanitary and unsavoury Seoul followed, and then a journey by sampan up the south branch of the Han River, which was previously almost unknown to Europeans; then up the north branch of the river, and on ponies to the Diamond Mountains, and northward to Wönsun on the east coast. Returning to Chemulpo by sea, Mrs. Bishop was strongly advised by the British Consul to leave the country, and so crossed to China and made her way via Newchwang into Manchuria It was a journey full of interest and of danger from floods, and the undisciplined Chinese armies on their way to the Korean war. Then she went vid Nagasaki to Vladivostok, studied the Korean colonies in Siberia, and tried to enter Korea from the north; but the rivers were impassable, and another long sea-voyage was necessary. A second residence in Seoul led to a journey northward along the old road to China for 200 miles. A third and final visit to Seoul occupied the last few months of 1896. As Mrs. Bishop lived in the village inns when travelling, and was in constant communication with the diplomatic agents and missionaries while in the capital, her opportunities for seeing native life and learning the state of affairs in the country were exceptionally good.

Her special study was the people. In a note we learn

that the average size of 1060 men, measured at Seoul in January 1897, by Mr. A. B. Stripling, was height 5 ft. 11 in., chest-measurement 31 in., and circumference of head 21 in. The maximum figures were respectively 5 ft. 11 in., 394 in., and 23 in. The physique is generally good, and the people possess many amiable qualities. The total population is estimated at from 12,000,000 to 13,000,000. Most of the people are very poor, and have no inducements to thrift; any wealth they may gather is at the mercy of the official class, who are mainly, if not entirely, responsible for the miserable condition of the country. Under the just rule of the Russians in Eastern Siberia, Mrs. Bishop found the Korean emigrants happy and enterprising, making good profits from their farms and inhabiting comfortable houses. Given good government, people and resources being as they are would ensure prosperity to Korea. Into the tangled political history of the unhappy country we cannot enter here, nor can we refer to the many curious customs, ceremonials and beliefs, which are set forth at considerable length. These, perhaps, constitute the most valuable part of the book, for Mrs. Bishop caught Korea in an interesting transition period, when the old subjugation to China was being repudiated for ever, and reforms of many kinds were being introduced. The Altar

of the Spirits of the Land, at which the ceremony of repudiation was carried out, is shown in Fig. 2. Few contrasts are more striking than that presented by Seoul at her first and at her last visit; when the filthy chaos of huts surrounding the palace gave place to well-ordered streets of good houses. The problem of the fourfold influence of Russian, Chinese, Japanese and European interests is very well handled. Of the industries of Korea the most interesting is the cultivation of gin-seng, the description of the processes employed in the manufacture of the dried root being, we believe, the fullest yet published.

The future of Korea is still uncertain, but it is bound to play a prominent part in the politics of the Far East; and this book will hold a place as a valuable work of reference for many years to come. HUGH ROBERT MILL.

ASTRONOMICAL RESULTS FROM THE
CAPE OBSERVATORY.1

TH HESE three volumes, issued under the superintend

ence of Dr. Gill, form in some respects a very remarkable production. Not so much on account of the very numerous observations, whose discussion furnishes forth these weighty books, as by reason of the widespread assistance rendered by many astronomers, whose energies Dr. Gill has quickened, whose results he has collected, stamped with his own individuality, and incorporated in the "Annals of the Cape Observatory." There are very few instances in which the director of an observatory has been willing to take up a laborious piece of work at the suggestion of an astronomer, however eminent, go through the wearisome task of making the observations, and then be willing to hand over his results to an independent authority for final discussion or criticism. It is this quality of self-abnegation, which strikes us as so complete and worthy of imitation. We congratulate Dr. Gill on his tactful skill, by which he

1 "Annals of the Cape Observatory." Vol. iii. The Cape Photographic Durchmusterung. Vol. vi. Solar Parallax from Heliometer Observations

of Minor Planets. Vol. vii. Solar Parallax from Observations of Victoria and Sappho. (London: Published by order of the Lords Commissioners of the Admiralty, 1896.)

has emerged from his self-imposed task, without friction with his collaborators, and been able to present to the world, in a complete form, the result of a scheme which he carefully planned and carried to a successful issue. We think it an especial merit in Dr. Gill's work, that he has perceived the value of strengthening his heliometer observations by combining with them the results made with similar instruments elsewhere. It was quite within his power and instrumental means to have derived the solar parallax from observations of the asteroids made solely at the Cape Observatory. Other observers could have done the same work, but separate discussions, made at irregular intervals and under varying conditions, do not possess the proportionate authority that attaches to one discussion made with several instruments on a combined plan. Moreover, one feels that the last word has been said, for some years at least, on this subject of solar parallax, by means of heliometer observations.

FIG. 2.-Altar of the Spirits of the Land.

Every observer must feel that, singly, he cannot do more than has already been done collectively. There can be no temptation to repeat the work. Consequently the owners of this class of instruments are freed from this particular investigation, for which the heliometer seems especially well fitted, and are at liberty to pursue other inquiries with advantage. It might be worth while just to mention, that to get the full power of a heliometer a considerable number of meridian observations is necessary. In this case some thousands came under the discriminating examination of Prof. Auwers. To use this mass of observations on one series of measures would be extravagant, but when combined with all the heliometer observations in a final inquiry, this cost of time and labour is disregarded, since they contribute to the increased accuracy of so large a body of measures. It is a true economy which Dr. Gill has practised, and the success which has followed it will bear much fruit in the future.

In the inquiry from which the solar parallax is deduced, we notice that no less than six observatories have contributed heliometer measures. Besides that of the Cape, we have New Haven (Yale College), Leipzig, Göttingen, Bamberg, and the Oxford Radcliffe Observatory, all furnishing measures of some or all of the three planets, Iris, Victoria, and Sappho, from stars in a previously selected zone, through which the planets passed. Several have further assisted by making a careful triangulation of the selected stars. The position