ture by reunion with the desiccating agent, and the communication of the heat evolved to pure water boiling at nearly the same temperature, but at a much higher pressure. But it is possible that, even without a duplication of this kind, advantage might arise from the use of a restraining agent. The steam, superheated in a regular manner, would be less liable to premature condensation in the cylinder, and the possibility of obtaining a good vacuum at a higher temperature than usual might be of service where the supply of water is short, or where it is desired to effect the condensation by air. RAYLEIGH. TWO AFRICAN EXPLORERS. WE regret to have to record the death of two of the best-known African explorers-Colonel J. A. Grant and Dr. Wilhelm Junker; the latter comparatively a young man, and the former by no means old. They belonged to two distinct types of African explorers: Grant was the true pioneer, who went out to force his way through an unknown region; Junker was the scientific student, content to spend years in one limited region in order to work out its geography, natural history, and ethnology. In The announcement of the death of Colonel James Grant, Speke's companion in the expedition for the discovery of the source of the Nile, has been received with widespread regret. The stalwart figure and genial, good-natured, boyish face of Colonel Grant has been familiar in London society and in geographical and scientific circles for more than twenty years. African exploration and in the younger generation of African explorers he took a keen interest to the last. He was a man of chivalrous loyalty to his friends. Speke's memory he almost worshipped, and it need scarcely be said that his feelings to Burton were of a very different stamp. Mr. Stanley had no more staunch supporter than Colonel Grant. Born in the parish manse of Nairn, in Scotland, in 1827, he was educated, like so many other Scots that have distinguished themselves in the service of the country, at the Grammar School of Aberdeen, and at Marischal College. At the age of nineteen he obtained a commission in the East India Company's service, and between that and the end of the Mutiny saw much active service, and won honours for bravery and devotion to duty. It is, however, as an African explorer that he claims notice in these pages. It will be remembered that in 1857 the only great lakes, of which we knew anything, in the map of Africa were Chad and Nyassa, the latter then quite recently plotted for certain by Livingstone. But rumours of other lakes had been filtering down to the coast for years. In 1857, Burton and Speke started from Zanzibar in search of "the Great Lake," as it was vaguely called; and, after a painful march of eight months, found Tanganyika, the first discovered of those great sheets of water which form so marked a feature of the centre of the continent. On the return journey, Speke took a run north, to find another great lake said to exist in that direction. He reached the southern shore of Lake Ukerewe, which has since become so well known as Victoria Nyanza. Though Speke only caught a glimpse of the southern waters of the lake, and had no adequate idea of its amplitude, he conjectured rightly that it must be the source of the Nile. Into the unhappy quarrel of Speke and Burton it is unnecessary to enter. But Speke, and not Burton, was selected by the Royal Geographical Society, in 1860, to lead an Expedition to the lake for the purpose of confirming his conjecture. This Expedition Government subsidized to the amount of £2500. Captain Grant, as he was then, was chosen to accompany Speke. The latter was, no doubt, the leader of the Expedition; but Grant, though he suffered much, and had to be carried a great part of the way, did much to render the expedition of scientific value. The unknown countries to the west and north-west of Victoria Nyanza were explored, though the contour of the lake was very inadequately laid down. Uganda was reached in 1862, and in July of that year the Nile was seen issuing fullborn from the lake, and dancing its way north-west over Ripon falls. The two travellers followed the river for 120 miles, but were compelled to quit it, and so missed the discovery of its connection with the Albert Nyanza. They came upon it again 70 miles further down, and reached Gondokoro in February 1863, where they were met and succoured by Samuel Baker. As might have been expected, the discoverers of the Nile sources received a great ovation on their arrival in England. Grant, like Speke, received the gold medal of the Royal Geographical Society, and was made a C.B. In 1864, under the title of A Walk across Africa," he published a narrative of the expedition. In 1872 he published "A Summary of the Speke and Grant Expedition" in the Journal of the Royal Geographical Society. Colonel Grant was a careful observer, and his "Walk across Africa" abounds in interesting facts and suggestions on country and people, especially on the latter. It was he who did the greater part of the scientific work on the Nile Expedition, and among other things he made a considerable collection of dried plants now in the Kew Herbarium. A rough list of these formed an appendix to Speke's "Journal of the Discovery of the Source of the Nile"; and most of the illustrations of this work were from drawings made by Grant. The publication of the first volume of Prof. D. Oliver's "Flora of Tropical Africa" fired Grant with the desire to have a special volume prepared on the flora and fauna of the Expedition. The result was that the whole of the twenty-ninth volume of the Transactions of the Linnean Society was devoted to the flora, and it is one of the most interesting of the series. The purely botanical part was contributed by Prof. Oliver and Mr. J. G. Baker; and the 136 plates (prepared at Colonel Grant's expense) illustrating the new or otherwise specially interesting plants, are some of the best work of the late W. H. Fitch. In 1871 Grant was elected a Fellow of the Linnean Society, and in 1873 of the Royal Society; and many other distinctions were conferred upon him, including a Companionship of the Star of India for his military services in India and Abyssinia. Dr. Johann Wilhelm Junker was a different type of explorer. He was born in Moscow, of German parents, on April 6, 1840. He spent his boyhood in Göttingen, attended the German Gymnasium at St. Petersburg, and studied medicine at Göttingen, Berlin, and Prague. After a visit to Iceland, Junker went to Tunis in 1874, and to Egypt in 1875. In that year he began those explorations which, with one or two interruptions, he carried on continuously for twelve years. He visited Lake Mareotis, the Natrön Lakes, and the Fayum. In 1876 he went from Suakin, through the Khor Baraka, to Kassala and Khartum; he explored the lower Sobat, and made successive journeys among the western tributaries of the Nile. In 1876 he proceeded as far westwards as Makaraka, and in 1877 crossed the Tangi River and visited the Wau, thus overlapping the route of Schweinfurth (1869–70). Indeed, Junker, during his many years' journeying, did a great deal to supplement the work of his distinguished predecessor. After a brief visit to Europe (1878), Junker was back in Africa in 1879, this time accompanied by a photographer (Bohndorff), who also lent a helping hand in preparing the numerous natural history collections. He accompanied several of the expeditions sent out by the Egyptian authorities from Khartum. But Junker often wandered almost alone, with very few native companions, and as a rule he was everywhere well received. To him we are indebted for much of our information on the Monbuttus and their country, the A-Sandeh and the various other tribes that inhabit the wide region watered by the Western Nile tributaries and some of the northern feeders of the Congo. Indeed, much of Junker's work lay in that extremely interesting country which forms the water-parting between the basin of the Nile and the Congo, and his hydrographical observations form some of the most important results of his many years' travels. To him may be said to be due the first steps in the solution of what was long known as the Wellé problem. The Wellé, which Schweinfurth came upon near its sources, was, even up to 1886, conjectured by many to be the upper course of the Sharé, which runs into Lake Chad. Junker struck the river at various places, one as far west as 22 40′ E.; but it was not until Grenfell and Van Gèle followed the Mobangi up from the Congo that the Wellé was proved to be one of the chief northern feeders of the Congo. But this is only one of many services rendered by Junker to the scientific geography of Africa. His investigations into the ethnology of the whole of this intensely interesting region are of the first importance, and his collections both in ethnology and in natural history now form some of the most prominent exhibits in the great Museum of St. Petersburg. Junker was an admirable specimen of the scientific explorer, and his twelve years' researches in the Soudan entitle him to be classed with Schweinfurth and Nachtigal, Wallace and Bates. Junker was in the heart of the Soudan when the Mahdist revolt reached a crisis. He had the greatest difficulty in escaping, and it was only after long detention that he reached Europe via Lake Victoria, Zanzibar, and Egypt. He made many friends in London when he came here to receive the gold medal of the Royal Geographical Society, which he well deserved. NOTES. MRS. ADAMS wishes us to say that she would be very grateful if former friends and scientific correspondents of the late Prof. J. C. Adams would be so kind as to send to her care any of his letters still in their possession. Their doing so would much assist in the preparation of a memoir. All letters so intrusted will be carefully returned. THE Electrical Committee of the Royal Commission for the Chicago Exhibition are anxious that the electrical department of the Exhibition should contain a good representation from this country. They have accordingly issued a circular letter on the subject, and it may be hoped that this will receive the careful attention of all who are in a position to facilitate the Committee's arrangements. The Committee especially desire that the Exhibition may display the very large share which English electricians have had in the development of electrical science and its practical applications. It is hoped that the fine collection of historical apparatus in the possession of the Post Office may be shown, and this will be supplemented by contributions which will be sought from many other sources. Although practical electric lighting has made greater progress in America than in this country, the Committee think there is much that England can show electricians on the other side of the Atlantic; and firms who devote special attention to the domestic uses of electricity and its artistic application are reminded that it may be to their interest to send to the Exhibition good specimens of their work. There will also be excellent opportunities for the manufacturers of electric railway signals, and for electrometallurgists. ON January 1, no fewer than 2082 applications for space at the Chicago Exhibition had been received from intending exhibitors in the United States alone. The number at the Philadelphia Centennial on the corresponding date was 864. Many applications have come from foreign countries, and it is expected that the exhibitors will be more numerous than at any previous "World's Fair." The allotment of space is to be made about June. The reception of exhibits will begin on November 1 next, and continue until April 10, 1893. WE regret to have to record the death of Mr. H. W. Bates, F.R.S. He was sixty-seven years of age. Of his well-known book, "The Naturalist on the River Amazons," Darwin said that it was "the best work of natural history travels ever published in England." His "Contributions to an Insect Fauna of the Amazons Valley," printed in the Transactions of the Linnean Society, were described by the same high authority 'one of the most remarkable and admirable papers he had ever read in his life." Mr. Bates is widely known as the discoverer of the principle of mimicry in the animal world. For twenty-seven years he was the acting secretary of the Royal Geographical Society. as WE have received an intimation of the death of Dr. Pieter Willem Korthals, at the advanced age of eighty-four years. He was for many years in the Dutch East Indian Service, and published a considerable number of papers on the botany of Sumatra, Borneo, and Java, the most noteworthy of which form a folio volume entitled "Verhandelingen over de Natuurlijke Geschiedenis der Nederlandsche overzeesche Bezittingen," edited by C. J. Temminck, 1839-42. This work contains seventy coloured plates of excellent execution. Dr. Korthals's first botanical paper appeared in 1830, and dealt with the genus Nepenthes; and his last, so far as we are aware, appeared in 1854. He was a Knight of the Dutch Order of the Lion. THE Council of the Royal Society of Edinburgh have awarded the Keith Prize for 1889-91 to Mr. R. T. Omond, for his contributions to meteorological science; and the Makdougall-Brisbane Prize for 1888-90 to Dr. Ludwig Becker, for his paper on The Solar Spectrum at Medium and Low Altitudes." THE Grand Gold Medal of the Paris Geographical Society has been awarded to M. Reclus. A gold medal has also been awarded to the Prince of Monaco for his researches on marine currents. SIR JOHN COODE, Past-President of the Institution of Civil Engineers, was last Friday elected by the Committee of the Athenæum Club a member, under Rule II., which provides for the annual introduction of a certain number of persons of distinguished eminence in science, literature, or the arts, or for public services. THE third Congress on anthropology in relation to crime will be held at Brussels from August 23 to September 3 next. ON Monday Lord Cowper called attention in the House of Lords to the subject of technical instruction, and to "the difficulties in which County Councils were placed by not knowing whether or not they could rely upon a permanent annual Government grant for its promotion." Lord Cranbrook, in the course of his reply, said he did not believe any Government would repeal the Act in accordance with which the Councils had received the money which was being devoted to technical education. So far as the present Government were concerned, they had not the smallest intention of repealing the Act or of taking the money for any other purpose. AT a Conference on technical education, held in Edinburgh on October 29, 1891, a general committee was appointed to consider the subject. This general committee in turn appointed a sub-committee to report on the amendments necessary in the laws relating to technical education in Scotland. The report of the sub-committee has now been issued; and appended to it is an official statement to the effect that the general committee, while approving of the suggestions made in the report, is of opinion that the Government ought to take an early opportunity of dealing with the question of technical and secondary education in a comprehensive measure, and that, for the efficient supervision of technical education, wider administration areas than the parish are required. A IN pursuance of his botanical expedition to Persia, Herr J. Bornmüller arrived at Batoum on December 24. Thence he intended proceeding to Teheran by way of Tiflis and Baku, and then, as rapidly as possible, to the south of Persia. The expedition is intended to extend over two years, and Herr Bornmüller does not intend to collect more than from fifteen to twenty sets of the plants obtained. Orders for sets should be sent to Herr R. Huter, Sterzing, Tirol. MR. JAMES BRITTEN AND MR. G. S. BOULGER intend to issue (to subscribers) in June next, their "Biographical Index of British and Irish Botanists," reprinted, with additions and corrections, from the Journal of Botany, and brought down to the end of 1891. As the promises of support at present received will not cover expenses, they will be glad to receive the names of additional subscribers, addressed to the care of the publishers of the Journal of Botany. ACCORDING to a telegram from New York, one of the finest displays of the aurora borealis ever known in that latitude was observed on the evening of February 13. The phenomenon stretched over a great belt of territory from Iowa to the Atlantic. A peculiar effect was produced on the telegraph system, and for intervals of three or four minutes at a time the wires New York and Albany it was possible to send messages without were so surcharged with atmospheric electricity that between the aid of the regular batteries. The current, however, was intermittent, and the effect unsatisfactory. For nearly two hours ordinary business could not be transacted with any degree of exactness. northern heavens, and was beautifully marked, the colouring The aurora seemed to occupy the whole of the being clear and distinct. People at first feared that a great fire was raging. DR. A. WOEIKOF, of St. Petersburg, who is engaged on an investigation into the cause of the famine in Russia, writes to the Meteorologische Zeitschrift that it is chiefly due to drought from August to October 1890, which injured the winter crops; to partial and insufficient snow, which melted early in the THE ceremonies in connection with the tercentenary celebration of Trinity College, Dublin, will begin on the morning of July 5, and conclude on the evening of July 8 next. Invitations were sent to most of the Universities and learned Societies in Europe, America, and the colonies, during last term; and replies have been received from many sending representatives, including Aberdeen, Athens, Bern, Cambridge, Christiania, Edinburgh, Erlangen, Giessen, Heidelberg, Johns Hopkins, Lausanne, Leyden, Madras, Naples, Smithsonian Institute, Sydney, Toronto, &c., and acceptances are daily arriving. large number of acceptances have also been received to the numerous personal invitations. Among the men of science who intend to be present are Sir F. Bramwell, Geo. Darwin, Thiselton Dyer, J. Evans, D. Ferrier, M. Foster, Sir A. Geikie, H. Hertz, J. W. Judd, Ray Lankester, Sir J. Lister, Sir J. Lubbock, Baron Nordenskiöld, Sir J. Paget, Lord Rayleigh, Sir G. Stokes, and Sir W. Turner. While the programme of the celebration has not yet been finally approved of, it ill probably include the following:-On the Tuesday morning there will be a reception by the Provost of Trinity College of all the invited guests; then a short full choral service in St. Patrick's Cathedral; in the afternoon a garden party; and in the evening a civic ball. On Wednesday morning there will be the presentation of addresses of congratulation from the various Universities, and in the evening a grand banquet, at which it is expected that over five hundred guests or members of the University will be present. On Thursday morning there will be a special Commencements for the conferring of a number of honorary degrees; after which there will be an adjournment from the Senate House to the College Park to witness the College races, held under the auspices of the College Athletic Club; in the evening there will be a special spring, and was followed by frost in April; and lastly to droughts amateur dramatic performance. On the Friday morning there will be a gathering of the students to hear short addresses from some of the distinguished visitors; in the afternoon, a concert given by the members of the University Choral Society; and in the evening, the students' ball. Numerous committees are daily engaged working out the multifarious details. these has been charged with the superintendence of the publication of an illustrated volume, which is to give the past and present history of the College, the publication of which volume has been undertaken by the firm of Messrs. Marcus Ward and Co. ON April 1, 1841, Sir William Hooker began his duties as Director of Kew. In the year 1891, therefore, the establishment might have celebrated its jubilee as a national institution, and it seemed to Mr. Thiselton Dyer that he might fitly mark the occasion by giving in the Kew Bulletin some account of the origin and development of the Royal Gardens as a place of botanical study. This intention he has now partly carried out, the December number of the Bulletin-which has just been issued-being entirely devoted to the subject. The narrative is one of great interest, and has evidently cost the author much hard work, as scarcely any authentic records exist of the period before 1840, when the Gardens were a purely private possession of the Crown. He has thus had "to fall back on local traditions, on local histories, the statements in which are often confusing and inaccurate, and on such scattered notices as could be gathered from contemporary literature." In the present instalment, the story is brought down to the year 1841. The history of the last half-century will be given in another number. NO. 1164, VOL. 45] One of and hot winds from May to July 1891. In the southern portion of the Government of Samara the prospects up to June 10 were excellent, but the harvest was destroyed by two days of hot provinces also, where the winter crops had greatly suffered, a winds, on June 14 and 15. And in the southern central moderate harvest was hoped for after the middle of July, but four hot days, from July 13 to 16, quite destroyed the crops. THE Journal of the Scottish Meteorological Society (third series, No. 8) contains a very interesting paper on silver thaw at Ben Nevis Observatory, by R. C. Mossman. The phenomenon is somewhat common at that Observatory, and occurs during an inversion of the ordinary temperature conditions, the temperature being considerably lower at the surface than at higher altitudes, causing the rain to congeal as it falls. In the six years 1885-90, 198 cases of silver thaw were observed, with a mean duration of 4 hours in each case, and they nearly all occurred between November and March, during times of perfectly developed cyclones and anticyclones. An examination of the weather charts of the Meteorological Office showed that for the 198 days on which the phenomenon was observed, the distribution of pressure was cyclonic on 137 days, and anticyclonic on 61 days. In anticyclonic conditions there was a cyclonic area central off the north-west coast of Norway, while the Isles. centre of the anticyclone was over the south of the British In cyclonic cases, an anticyclone lay to the south, over the Iberian Peninsula. The lowest temperature at which the phenomenon took place was 18°, and was rarely below 27°. Fully 90 per cent. of the cases occurred when the thermometer was between 28° and 31°9, so that the greater number of cases occurred just before a thaw. The most common type of cloud which preceded both cyclonic and anticyclonic cases of silver thaw was cirro-cumulus, frequently accompanied by cirrus and cirro-stratus; and the changes showed that the higher strata of the atmosphere came first under the influence of the moist current, which took from three to eight hours to descend to the height at which cumulo-stratus forms. An examination of a series of storm charts prepared by Dr. Buchan disclosed the somewhat remarkable fact that 73 per cent. of the cyclonic, and 63 per cent. of the anticyclonic cases of silver thaw on Ben Nevis were followed or preceded by gales on our northern and north-western coasts; and it would appear from the wind conditions that the barometric gradient at the height of Ben Nevis (4407 feet) must be totally different from what obtained at sea-level during the occurrence of silver thaw on the hill-top. Many of our readers will remember the remarkable case of silver thaw which occurred in London last Christmas Day. THERE has been much talk in Germany about Dr. Peters's discovery of saltpetre in the Kilima Njaro district. This discovery accords with statements which were already well known. Dr. Fischer, after an examination of the Donjongai volcano, reported that in the neighbourhood of the crater there were a series of curiously shaped veins of a white substance which he took to be either saltpetre or soda. In 1879, Herr Jarler asserted that large quantities of sulphur would probably be found in the crater. The Berlin correspondent of the Times, by whom these facts are noted, adds that not far from the volcano there lie great swamps from which soda is obtained. It is expected that an expedition for the exploration of the district will soon be sent out by the German East Africa Company. PROF. A. GIARD calls the attention of naturalists to a new case of mimicry between two very different insects (the one Hymenopterous, the other Dipterous)-Athalia annulata and Beris val lata. When both insects are quiet, the resemblance of colour and patterns is perfect, and as the Athalia, like most Tenthredinæ, is protected against birds and other foes by its unpleasant smell, it is probable that the resemblance is of considerable service to Beris. M. Giard also refers to the larva of Allantus tricinctus which is commonly found on the leaves of plants, vividly coloured, and quite conspicuous, but resembling in form and colour birds' droppings, as is the case with a spider described by H. O. Forbes. THE number of persons who approve of cremation seems to be steadily increasing. From the Report of the Cremation Society of England for 1891, we learn that in 1885, the first year the crematorium at Woking was used, only three bodies were sent there; in 1886 the number was 10; in 1887, 13; in 1888, 28; in 1889, 46; in 1890, 54; and during the past year, 99. Crematoria are being built in various parts of the country. At Manchester a crematorium is in course of erection, and will, it is thought, be completed and opened for use during the coming spring. A company has also been formed, and is making rapid progress, with the same object at Liverpool; and the City of London Commission of Sewers is taking steps to obtain powers to erect a crematorium at their cemetery at Ilford. The Cremation Society at Darlington, and other associations, are moving in the same direction. A SMALL axe of nephrite, found at Ohlau, in Silesia, and now in the Roman-German Museum at Mainz, has lately been carefully examined by Dr. O. Schoetensack, with a view to the discovery of the source from which the material must have been obtained. From a thorough determination of its specific gravity, microscopic structure, and chemical composition, Dr. Schoetensack concludes that the nephrite is exactly the same as a mineral which has been found by Dr. Traube near Jordansmühl, in Silesia. There is no reason, therefore, why the axe should not be pronounced to be of Silesian origin. This is the only prehistoric object of nephrite, found in Europe, the source of which has been definitely decided. PROBABLY few authorities responsible for the making and maintenance of roads are aware that one of the things against which they should be on their guard is the use of rotten flints for macadamising purposes. Mr. C. Carus-Wilson has been letter to a local journal, states the conclusions at which he has giving some attention to this subject at Bournemouth, and, in a arrived. He was led to consider the matter by the abnormal quantity of slush on the surface of Poole Road. This he attributes to the fact that the road has again and again been mended with rotten flints, by which he means flints that have become decomposed to such an extent that there is very little true flint left. These flints are surrounded by a thick zone of soft white material. This is rapidly removed from the flinty nucleus by the grinding and pressure to which it is subjected; while the true flinty nucleus, being thus denuded of its outer covering, becomes too small to bear much crushing weight, so that it quickly breaks up, and forms a fine flint sand. Mr. CarusWilson has found by repeated microscopic analysis that the Poole Road mud is formed principally of these two substances. THE Journal of the Society of Arts prints this week an interesting lecture on burning oils for lighthouses and lightships, by E. Price Edwards. It was delivered at a meeting of the Society on February 10. After the lecture Sir Lyon Play fair, who was in the chair, said it was quite clear that mineral oils must in time beat the vegetable oils, on account of their chemical composition, the ingredients in the latter not being all combustible, but consisting of fatty acids and glycerine. Mineral oils, on the other hand, were nearly of the same composition as olefiant gas, the illuminating constituent of coal gas, with the addition of a little more hydrogen. They were therefore sure to win in the end; it was merely a question of manufacturing them safely. Eastern AT the meeting of the Field Naturalists' Club of Victoria on December 14 last, Mr. A. J. Campbell read a paper on a nest and egg of a bird of paradise (Ptiloris victoria). Australia possesses a genus (three species) of these beautiful birds, but they are very seldom seen. The nest was found on November 19, by Mr. Dudley Le Souef and Mr. H. Barnard during a visit to the North Barnard Islands, about forty miles off the coast from Cardwell, Queensland. They watched the hen bird for some time, and saw her fly into the crown of a Pandanus tree growing close to the open beach. Although they could not distinguish the nest itself, they could see the head of the bird as she sat on it. The nest was about 10 feet from the ground, and the bird sat quietly, although they were camped about 5 feet away from the tree. There was a single egg, the incubation of which was probably about seven days old. The nest was somewhat loosely constructed of broad dead leaves and green branchlets of climbing plants and fibrous material. Inside were two large concave-shaped dead leaves underneath pieces of dry tendrils which formed a springy lining for the egg or young to rest upon. The following is the measurement in centimetres over all, 19 broad by 9 deep; egg cavity, 9 across the mouth by 4 deep. DOVE's observation that when a tuning-fork of proper pitch is held to each ear beats can be heard, where there is no possibility of interference of the sound-waves in the air, is confirmed by Dr. W. Scripture (Wundt's Philosophische Studien), who further gives experimental ground for rejecting the hypothesis of transference of the sound through the bones of the head of the Eustachian tubes. Difference-tones, on the other hand, If we may judge from the progress of the Photographic Society of India, photography is rapidly becoming more popular among Anglo-Indians. In January 1891, there were 277 members on the Society's books; now there are over 310. THE Oesterreichische Botanische Zeitschrift for February contains a very full account of the results of Porta and Rigo's visit to Spain in 1891, and of the species gathered by them on their journey. WE have received Parts 10 and II of the "Illustrations of the Flora of Japan," published at Tokyo. The drawings continue excellent; the diagnoses are unfortunately in Japanese. MESSRS. DULAU AND CO. have issued a catalogue of botanical works which they offer for sale. It contains the titles of about 3000 writings relating to geographical botany. burning jet can be obtained, the hydrogen in contact with the palladium being then subjected to a certain amount of compression. The palladium is now heated a little more strongly, just above bright redness, when it is no longer capable of occluding hydrogen, and then the lamp is withdrawn, and after a few strated in a most striking manner, for the stream of hydrogen seconds the stopcock closed. The occlusion is then demoncontinues to bubble through the sulphuric acid bottle and into the U-tube for several minutes with its original rapidity, although all exit is prevented by the closing of the stopcock. At length, however, the occlusion diminishes, and the stream of hydrogen gradually becomes slower and slower, until it entirely ceases, the palladium having regained the temperature of the room, and become saturated with hydrogen at this temperature. If now the stopcock is opened, and the metal again heated, upon applying a flame to the jet, the issuing hydrogen evolved from the palladium takes fire, and burns with a tall flame which remains constant for some minutes, then, as the hydrogen stored in the palladium becomes exhausted, diminishes in size, and finally disappears. The moment the flame is removed occlusion instantly commences again, and the experiment may THE "Electrical Trades Directory," issued by Mr. George be repeated any number of times with undiminished effect. Tucker on behalf of the Electrician, has made its tenth annual appearance; and no effort has been spared to bring it up to date. The biographical division of the work contains sketches of the careers of 260 men who are well known in the electrical world. These sketches have all been revised by the subjects of them. No fewer than 28 of these notices are accompanied by portraits, among which is a portrait of Prof. Ayrton from a specially engraved steel plate. THE Royal University of Ireland has issued its Calender for the year 1892. THE additions to the Zoological Society's Gardens during the past week include a Herring Gull (Larus argentatus), six Common Gulls (Larus canus), five Black-headed Gulls (Larus ridibundus), British, presented by Mr. T. A. Cotton, F.Z. S.; a Roseate Cockatoo (Cacatua roseicapilla) from Australia, a Grey Parrot (Psittacus erithacus) from West Africa, presented by Mrs. Hennah; a Red-winged Farrakeet (Aprosmictus erythropterus) from Australia, presented by Lieut.-Colonel R. J. H. Parker, R. E.; a Cape Dove (Ena capensis) from South Africa, presented by the Rev. George Smith. OUR ASTRONOMICAL COLUMN. PHOTOGRAPHIC MAGNITUDES OF STARS.-The AstronomerRoyal communicated a paper "On the Relation between Diameter of Image, Duration of Exposure, and Brightness of Objects in Photographs of Stars taken at the Royal Observatory, Greenwich,' to the Royal Astronomical Society in January. First, with regard to the relation between the diameter of the image of a star on the photographic plate and the time of exposure. Measures of a large number of stars have led to the development of the following empirical formula for the same star with different exposures √d=103 log + const., By where d = the diameter of a stellar image in seconds of arc, and the exposure in seconds of time, the magnitude, m, being expressed on Pogson's scale. This relation represents the observations through a range of eight magnitudes, with a mean apparent error of less than one-twentieth of a magnitude. using the measures from which the above formula was deduced, and photometric determinations of magnitude made at Bonn and Oxford, data were obtained for determining whether there was a constant relation between duration of exposure and brightness of star photographed, whether, in fact, for equal diameters of images AN experiment, illustrating the remarkable power possessed by palladium of occluding hydrogen, is described by Prof. Wilm, of St. Petersburg, in the current number of the Berichte of the German Chemical Society. The experiment is so simple, and requires so short a time to exhibit, that it would appear to be eminently suitable for lecture demonstration. The metallic palladium is employed in the finely divided state obtained by heating the easily prepared yellow crystals of the compound PdCl . 2NH3, first in the open air, and subsequently for a short time in an atmosphere of hydrogen. A small quantity, about four grams in weight, of the palladium so obtained is placed in a bulb blown at the bend of a U-shaped tube. The extremity of one limb of the U-tube is bent round at right angles, and connected with a wash-bottle containing sulphuric acid, which in its turn is connected with a Kipp's apparatus generating hydrogen from zinc and dilute sulphuric acid. The wash-bottle serves not only to dry the hydrogen, but also to indicate the speed of the current of gas. The extremity of the other limb of the U-tube is narrowed to a capillary, and terminates with a tightly-fitting stopcock and jet. In commencing the experiment, the hydrogen current is started, and then, first the metal, and afterwards the whole U-tube, is carefully heated with a Bunsen flame in order to remove the moisture formed by the action of the hydrogen, under the influence of the palladium, upon the oxygen of the air contained in the apparatus. When all the air and moisture are thus driven out of the apparatus, an attempt may be made to ignite the issuing hydrogen at the jet above the open stopcock. It will be found, however, that even while the metal is hot and the stream of hydrogen very rapid, a constantly burning flame cannot be maintained at the jet with the stopcock fully open; instead, a series of somewhat explosive ignitions and sudden extinctions occurs. It is only when the stopcock is turned so as to reduce the exit of the gas to a minimum that a constantly connecting magnitude, diameter of image, and time of exposure. Exposure x brightness = const. 0'4 x m = log const., in which 04 is the logarithm of the number expressing the magnitude-ratio. By combining the two relations developed, it follows that, for the same exposure Magnitude of star = const. 2:43 × diameter. And finally the three formulæ are expressed by the following :m = 2.5(logi – 0·97 d) + const., - |