WE learn from Science, that an endeavour is being made to establish a permanent scientific head for the U.S. Department of Agriculture. An amendment to the Agricultural Appropriation Bill has just been sent to Congress providing for a "Directorin-Chief of scientific bureaus and investigations, to serve during

good behaviour, to have authority to act as Assistant Secretary, and to perform such other duties as the Secretary may direct." This amendment is, we understand, the outgrowth of an effort

to secure a permanent non-political organisation and administration of the various bureaus and divisions engaged in the scientific work of the Government, and at the same time bring about a more intelligent and more effective cooperation than has been heretofore possible. The Department of Agriculture as at present organised comprises a large number of scientific and administrative divisions having for their object the discovery, exploration, and development of the agricultural and other natural resources of the country. The scientific divisions are engaged in researches requiring the highest technical skill, and some of them in the solutions of problems requiring long years of preparation and scientific training. Our contemporary adds that, should the amendment become a law, it is by no means improbable that other scientific bureaus of the Government will seek the protection and support provided thereby, and that in the near future the United States may boast of a National Department of Agriculture and Science.

THE Russian National Health Society is reported by the Lancet to be making strenuous efforts for the success of the Jenner centenary celebration to be held in May. Although the method in which the Society proposes to commemorate Jenner's great discovery has already been referred to in these columns, a statement of the first arrangements will be of interest. There are offered four prizes, the first equivalent to 100 guineas, and a gold medal, for the best work upon vaccination. English is one of the languages in which the work may be written, and the work must be sent in before March 12 (New Style). An exhibition of relics of Jenner, and of books, pamphlets, prints, tabular returns, instruments, and other objects relating to vaccination or to Jenner will be held. The Society is also publishing a history of the development of vaccination in Russia and other countries, and a full biography of Jenner, together with a portrait, and copies of his drawings. The price of this "centenary edition" which will be edited by Dr. Ladislas Hubert, the Secretary of the Society, will be three roubles (about 65.). All objects intended for the exhibition, as well as any other communication relating to the centenary, should be addressed either to Dr. Hubert, 15 Dmitrofski Pereoulok, St. Petersburg, or to Dr. F. Clemow, 69 Earl's Court Square, London, S. W., who is acting for the Society in England.

REUTER'S correspondent at St. Petersburg states that the subjoined telegram from Irkutsk was received there on Tuesday-The Governor of Irkutsk, in reply to inquiries, has received the following from Yakutsk : 'Peter Ivanovitch Kuchnareff, who trades at Ust Yansk, by a letter dated November 10, communicated the following to the merchant Kuchnareff at Yakutsk :-'We learn that Dr. Nansen's expedition has reached the North Pole, has discovered a hitherto unknown and, and has now returned." In order to verify the news and n case of necessity to render assistance to the expedition, the Governor of Yakutsk has instructed a member of the adminis tration in the Verkhoyansk district to proceed to Ust Yansk.

A BRIEF Summary of the facts concerning the Panama Canal, together with a few words as to the present status of the canal construction, are given in the February number of the National Geographic Magazine, by Mr. R. T. Hill. So many misstatements are made as to the condition of the works, that Mr. Hill's rticle, and the illustrations which accompany it, will do good ervice in refuting them. It appears that the plant of the Company is not undergoing the ruinous decay that has been represented, both in this country and America, but, on the contrary, it is kept in scrupulously good order, and will be available for the completion of the work, should the Commission which has to report upon the affairs of the late Company decide to carry out the scheme. That the Commission does not consider the route impracticable is attested by the fact that they have kept the work

progressing, about two thousand labourers having been employed upon the construction of the canal during last year. When, in February 1895, Mr. Hill took the photograph reproduced as an illustration to his article, he counted five locomotives at work carrying away the excavations from the Culebra summit. I: was reported recently that the money to finish the work on the present plan has all been furnished, and that two thousand more men from Jamaica and other West Indian islands are being collected, the intention being eventually to increase the force to six thousand men. It is expected that the work will be completed in six years.

WITH reference to excavations of the island of Philae. the Cairo correspondent of the Times writes, under date February 17:-" The work of clearing the island of debris S as to permit a thorough examination of the ancient monuments, which was entrusted by the Egyptian Government to Captain Lyons, R. E., will probably be completed next month. The satisfactory discovery has been made that the foundations of the main temple of Isis are laid upon the granite rock, being in some places over 21 feet in depth, and the temple has nearly as much masonry below ground as above. The south-eastern colonnade has also its foundations upon the granite, and, so far as excavated, they are curious if not unique in design. They consist of parallel cross walls some metres high, but varying according to the slope of the rock surface, with large stone slabs placed horizontally upon their tops, and the pillars forming the colonnade are erected upon the slabs. The nilometer is marked! in three characters-Demotic, Coptic, and another much older. probably Hieratic, of which a copy has been sent to Berlin for decipherment. A stela was found bearing a trilingual inscription in hieroglyph. No traces have been discovered of any buildings anterior to the Ptolemaic periods. M. de Morgar, Director-General of the Antiquities Department, is engaged upon repairing the great hall of columns at Karnak,”

66

AT the Royal Artillery Institution, Woolwich, on Thursday last, Dr. G. H. Bryan, F.R.S., lectured on Flight and Flyingg Machines." The lecturer pointed out that the power of flying hat been developed under more favourable conditions in small than in large animals, both because the risk to life and limb in the case

of a fall increased with the size of the animal, and also because, assuming De Lucy's law, large bodies required more power to sustain every pound of their weight in horizontal flight than small ones. These considerations applied equally to flying machines. As Lord Kelvin had said, Maxim's experiments ha-1 solved three of the five problems connected with artificial flight, and the two remaining ones were now solved by the soaring experiments of Lilienthal in Germany, and Pilcher in Britain. All that remained was to combine the advantages of Maxim's and Lilienthal's apparatus in a single machine, and in this Dr, Bryan prophesied that artificial flight would be accomplished at no distant date.

AT King's College, on Tuesday next, in continuation of the free lectures given to the public, in the theatre of the College, Prof. Bottomley will discourse on the "Romance of Plant Life."

Ar a meeting of the Royal Geographical Society, to be heli to-morrow afternoon, a plan for the geographical description of the British Islands on the basis of the Ordnance Survey will be submitted by Dr. H. R. Mill, and a discussion will take place upon it.

THE Council of the Society of Arts attended at Marlborough House on Wednesday, February 19, when H.R.H, the Prince of Wales, President of the Society, presented to Sir Lowthian Bell, Bart, F.R S., the Albert Medal, in recognition of the services he has rendered to arts, manufactures, and commerc

by his metallurgical researches and the resulting development of the iron and steel industries."

THE deaths are announced of Dr. G. Wagener, Professor of Anatomy in Warburg University; Dr. R. Benedikt, Professor of Technological and Analytical Chemistry in the Technische Hochschule at Vienna; Dr. Laennec, Director of the Nantes School of Medicine, and formerly Professor of Physiology; and Dr. Per Hedenius, Professor of Pathology, Hygiene, and History of Medicine in the University of Upsala; Dr. D. D. Slade, Lecturer on Comparative Osteology in Harvard University, and known for his contributions to osteology, zoology and botany.

·-

WE see from the Rendiconti of the Reale Istituto Lombardo, hat, at the recent annual meeting, one of the Cagnola prizes of 2500 lire and a gold medal of 500 lire was awarded to Prof. Ferdinando Sordelli for his treatise entitled "Flora fossilis Insubrie." The other Cagnola prizes were not awarded. Under the Brambilla bequest a sum of 300 lire and a gold medal was awarded to each of the following for having introduced useful industrial processes:-Messrs. Macchi and Izar, Augusto Stiegler, Anacleto Pastori, Fermo Coduri and Co., Casall Francesco and Sons, Carlo Galimberti and Co.; and 250 lire to Antonio Fusetti for his process of photo-engraving on copper. The Fossabi prize of 1000 lire for a work on arterio-sclerosis was awarded to a work sent in under the motto, Experientia street. The Ciani prize for the best Italian historical reading book was distributed among the following, who were awarded 500 lire each :-Prof. Francesco Bertolini, "Story of the Italian kevival"; Prof. G. De Castro, "The Mantua Processes and the 6th of February, 1853"; Prof. Pietro Orsi, "How Italy was made." Among the prizes proposed for 1897 are the following :An Institute's prize of 1200 lire for an experimental proof that an electrified dielectric is in a state of tension in the direction of the field and in a state of compression across it (last date, April 30, 1897). Cagnola prizes of 2500 lire each for works on the orographical conditions of the Alps and the Italian peninsula and islands; and the history of the methods and instruments for registering the phase of alternating currents (both April 30, 1896). Similar prizes for works on the comparative anatomy of the innervation of trophic organs, and on the role of pathogenic microbes in human pathology (April 30, 1897). Secco-Commeno prize of 864 lire for a work on the genesis, symptoms, effects, and cure of uremia (May 1, 1897). The Tommasoni prize of 500 lire will be given for the best work on the life and work of Leonardo da Vinci, with especial reference to his precepts on the experimental method, and to a project of a national publication of his entire works (May 1, 1896). The competitions enumerated are open to all nationalities, and the memoirs may be written in Italian, French, or Latin. The last-named may also be written in English or German. They must be sent to the Secretary of the Institute, at the Palazzo di Brera, Milan, before the dates named, under a motto or pseudonym, and a statement of the prize competed for.

In reference to the tenacity of life in insects, Mr. J. C. Warburg writes to the Entomologist. "When I was still new to collecting in South France, I discovered one day, to my great joy, a large female of Saturnia pyri hidden away in some bushes. The specimen was the first I had ever caught, and I decided, on account of its large body, to stuff it (a quite unnecessary operation; I have kept dozens since unstuffed). The moth was first apparently killed by being forced into a cyanide-bottle, where it was left about an hour. The abdomen was then emptied, and the cavity filled with cotton-wool soaked in a saturated solution of mercuric chloride. The insect, pinned and set, was discovered next day attempting to fly away from the setting-board."

THE effect of thunder, or the firing of cannon, on pheasants is very curious; either of these sounds start the cock birds crowing as if in defiance. Mr. G. T. Rope, writing to the Zoologist, says that at a place between five and six miles distant from the garrison town of Colchester, he has heard pheasants close to him echoing each report of the artillery practising there, and has on many occasions noticed the same thing elsewhere. The crowing sounds more like the answer to a challenge than the expression of fear. Mr. J. E. Harting points out that the observation is not new. Gilbert White remarked a century ago that the pheasants in his neighbourhood crowed when big guns were fired at Portsmouth, and the wind was blowing from that direction; and, says Mr. Harting, Charles Waterton also, in his Essays on Natural History" (first series, 1837), makes the following remarks on the subject :-"The pheasant crows at all seasons on retiring to roost. It repeats this call often during the night, and again at early dawn; and frequently in the day-time, on the appearance of an enemy, or at the report of a gun, or during a thunder-storm."

OUR American correspondent writes under date February 21:-" J. Frank Elline, of Baltimore, has demonstrated that ordinary calcium light will produce results similar to the rays from a Crookes' tube. By combining the calcium light with side X-rays, Mr Elline obtained a result directly the reverse of ordinary X-ray pictures, the shadows being darker than the background. Dr. Wellington Adams and Prof. Nipher, of Washington University, St. Louis, have demonstrated that the X-rays can be focussed. Edison is experimenting in the direction of taking pictures by snap-shots, and has already succeeded in reducing the time of exposure to seven seconds, getting clearly-defined images of strips of metal after the rays had penetrated a heavy piece of cardboard and a vulcanised plate. Trowbridge claims to have secured instantaneous results already. Edison reports that his eyes were sore after working for several hours with his fluorescent tubes; but he is not certain that this result is

specially attributable to the X-rays. Dr. Wm. J. Morton reports that he sees brilliant flashes of light after he has discontinued work, and, as he has worked with electrical light for many years without injury, he infers that the X-rays are injurious to the eye.

WITH reference to the statement in the foregoing note, as to the effect of Röntgen rays upon the eyes, Mr. Swinton informs us that though Mr. J. C. M. Stanton and himself have worked continuously with the Crookes' tubes for hours together, neither of them has experienced any ill-effects so far as their sight is concerned. In fact, so far as Mr. Swinton has observed, the X-rays do not, per se, in any way affect the eye, either at the time of the experiment or afterwards. With regard to Mr. Edison's experiments, a few seconds are found to be ample for taking pictures of pieces of metal. When it is a question of photographing a portion of the body, however, it is a different matter; but even then, with a good tube, thirty or forty seconds' exposure will give a very fair result.

DR. W. J. VAN BEBBER, of the Deutsche Seewarte, has sent us a separate copy of an interesting paper "On the climates of the earth and their influence on mankind," published in Globus (vol. Ixix. Nos. 6 and 7). After giving a general description of continental and ocean climates, and of the influence of mountains and forests, he discusses in some detail the peculiarities of climate of various zones, and traces their influence on diseases, especially on malarial fever and cholera in the tropics. He finds that the occurrence of the former is closely related to rainfall and temperature; the fevers begin with the rainy reason, usually reach their maximum by the time the rain abates, and decrease as cooler

weather sets in. The malady becomes acute when warm weather occurs after an inundation. During the present century there have been five great epidemics of cholera. In the origin and development of this disease the weather conditions are found to have different effects, according to the locality. In Bombay and Calcutta, for instance, it generally begins before the hot and rainy season, and decreases with increasing temperature and rainfall; while in other parts, cholera is most frequent towards autumn, and decreases with decreasing temperature. The occurrence of land and sea breezes (including monsoons) in various parts of the globe is discussed at some length.

THE relations of the weather to the spread of disease are still involved in obscurity. Prof. Cleveland Abbe defends the general atmosphere from calumny in this connection in the Monthly Weather Review (vol. xxiii. No. 8, 1895). History records that, in the fifteenth century, a plague epidemic broke out most violently in a Swiss town immediately after a cloud, coming from an infected but distant region, discharged its rain upon that town. But, as Prof. Abbe points out, without going back to the fifteenth century, there was an excellent opportunity to investigate the subject in 1889-90, when the influenza spread over the whole civilised word. Its progress was so regular that for a long time there was a general belief that the active germs of influenza were carried as dust in the air by the winds, or perhaps by the upper currents. This idea was dissipated by several memoirs that established the fact that the wind and weather were entirely subordinate factors, and that the spread of the disease followed the lines of travel, especially the principal steamboat and railroad routes, and that, therefore, the germs were carried by diseased individuals, or by articles that had been used by or had come in contact with them, and not by the winds. Of course the wind, in the narrow sense, may have carried the germs a few feet or rods from one individual to another, but not for distances of many miles. Several epidemics, such as the yellow fever, small-pox, and cholera, have been traced back to the direct importation of their contagia (whether animate or inanimate) by human agencies. Furthermore, experimental data show that few disease germs can maintain their vitality more than a few hours when freely exposed to the air and sunshine, as would probably be the case if they were carried in the atmosphere as minute particles of dust. Therefore Prof. Abbe thinks it probable that the winds and the rain must not be considered as the means by which diseases are spread between places that are any considerable distance apart.

PROF. SERGI (Centralblatt f. Anth. Eth., &c.) complains that the Indo-Germanic theory of the origin of European peoples has distracted attention from the Mediterranean peoples. For some time past these latter have been studied by him, of whom he recog nises four main branches-Lybian, Iberian, Ligurian, and Pelasgian. The Egyptian monuments state that the ancient Egyptians came from the land of "Punt," and anthropologists admit an African origin for that people. Sergi places Punt in Ethiopia, Somali-land, and part of South Arabia, and he finds the same head-forms amongst the ancient Egyptians and modern Somalis. This stock is known under the term "Hamitic," and it differs from the Semitic. Remains of prehistoric men from Spain, France, North Italy, &c., show a close resemblance with each other and with the early inhabitants of North Africa and the Canary Islands. Sergi asserts that the same people form to-day the bulk of the living populations of Spain, Italy, and Greece. He believes that the Hamites arose in East Africa; the first migration entered Egypt, then the stream diverged to the east to Syria and Asia Minor, and spread westwards as far as the Canary Islands; the Iberians, Ligurians, and Pelasgians (with the Etruscans) being branches of the main stem. These Mediterranean folk occupied South Russia, Switzerland, France, and

Great Britain. In Neolithic times they were exterminated in the valley of the Po and in Switzerland, were driven beyond the Loire in France, and to the south and west in Britain by the mighty Celts. He describes the physical features of this Mediterranean group as a whole, and declares it to be the most beautiful of all the varieties of man.

THE part of the Agricultural Gazette of New South Wales for December 1895, contains a number of papers on the cultivation of fruits, and other crops, and on the diseases which affect cultivated plants in the colony, showing the valuable results obtained by the establishment of a State Department of Agriculture.

IN the Irish Naturalist for February is a useful paper by one of Ireland, in which the island is parcelled out into forty districts. of the editors, Mr. R. L. Praeger, on the botanical subdivision served, and all the larger counties cut up into several divisions The geographical county boundaries are to a large extent preThe paper is accompanied by a map.

FROM the Skandinavisk Antiquariat, Copenhagen, has come to us a catalogue of a good collection of ancient and modern works on geography, ethnography, and travels, together with a number of rare maps and prints, offered for sale. A number of treasures to geographical bibliophiles will be found included in the catalogue.

THE 1896 Annuaire of the Observatoire Royal de Belgique has been issued without interruption since 1834), the contents has only just come to hand. As in former years (the publication are composed of ephemerides, containing the principal astronomical date for the current year; geographical, meteorological, and vital statistics; definitions of physical constants, and short articles, chiefly by M. Folie.

DR. G. EISEN reprints, from the Proceedings of the Californian Academy of Sciences, a paper entitled “Biological Studies of Figs, Caprifigs, and Caprification." He gives a history of the methods adopted from the earliest times for artificially pollinating the cultivated fig. While the ordinary edible figs grown both in Europe and in America, are independent of artificial pollination, the Smyrna fig will not mature without caprification, since the fig contains no male, but only female flowers.

WE have received a copy of a "Classificatory Chart of the Commoner British Orders of Flowering Plants," by Mr. W. P. Winter. That can hardly be regarded as an ideal selection of the more important orders, which excludes the Solanacex, Euphorbiacea, and Conifere, and admits the Chenopodiacer, Alismace.e, and Naiadeæ. But this is explained by the footnote that "the orders include those necessary for the Elementary Examination, South Kensington." The characters seem carefully drawn up, and the chart will be a useful one to students.

The

discovery of Rontgen, has afforded the photographic journals THE development of photography, brought about by the excellent opportunities for distinguishing themselves. special issue of the Photogram, brought out under the title of The New Light," has run into a fifth edition; and the Photographic Review for March, apparently aims at obtaining the same measure of success, for its pages are almost entirely devoted to and Dr. Hall Edwards with Rontgen rays. accounts and illustrations of work done by Mr. A. A. C. Swinton

WE again offer our congratulations to the Wellington College Natural History Society. The twenty-sixth annual report of the Society shows that during 1895 the knowledge of the men bers was improved by means of lectures, and the faculties of few ardent observers were developed. The Pender prize founded in 1879, for the best essay on some scientific subject

The term "anode rays" for the rays discovered with so much lat by Prof. Röntgen, whether they be the same as those previously discovered by Dr. Lenard or not, is suggested by remarks from Mr. A. W. Porter at a recent meeting of the Royal Society. They certainly do not start from the kathode, but from some opposed surface, a surface which may be an actual anode, and which always has some anodic properties. From each point of such a surface rays start in all directions; this is proved by the shadows they cast of slits, holes, and wires.

OLIVER J. LODGE.

I MAY state that in a lecture which I gave here on the evening of Tuesday last, the 25th ult., I showed to a large audience, by means of a sheet of barium platino-cyanide, rendered fluorescent by the Röntgen rays from a Crookes' tube, all the things referred to by Mr. Campbell Swinton in his letter in the last number of NATURE. The shadows of coins in a purse, and of a hand, were distinctly visible to the audience when placed behind screens perfectly opaque to ordinary light, and, though more dimly, even through a book of eight or nine hundred pages.

I must confess that I cannot see why, after Prof. Röntgen's account of his own work, the success of such experiments as those made by Mr. Swinton or myself should be regarded as surprising, or accounts of them received with incredulity. They seem to me to be merely a variation of Prof. Röntgen's own experiments, or at most to be a matter of the most obvious inference from these experiments.

The statements that have appeared to the effect that Signor Salvioni has devised a method of rendering the retina of the human eye sensitive to Röntgen rays, and that by his method objects are directly seen through planks of wood, sheets of aluminium, &c., are simply absurd. The fluorescent light produced is entirely distinct from the Röntgen rays, and affects the retina like ordinary light; and of course parts of the sheet which do not fluoresce, because they are shielded by the opaque objects behind from the Röntgen rays, appear dark. Seeing such shadows can no more be said to be seeing the objects themselves by means of the Röntgen rays, than a man can be said to see himself when he looks at his shadow thrown by an ordinary gas-lamp on the street.

1

Prof. Röntgen discovered the fluorescence of the barium platino-cyanide under the rays now called by his name, and the transparency of ordinarily opaque matter to these rays, and the discoveries of Signor Salvioni and others, so far, at any rate, as they have been described in NATURE and other journals I have seen, amount to nothing more. It is only just that in accounts of verifications of Röntgen's discoveries an attempt should be made to show clearly that such observations are only verifications, so as to prevent the credit of discovery which is Prof. Köntgen's due from any appearance, however unintentional, of indirect diminution.

Scientific accounts of verifications, as far as I have seen them in NATURE or elsewhere, are in themselves unexceptionable; but extra precaution seems necessary in order that the public should not be led by newspaper paragraphists, retailing such accounts at second-hand, to regard as extensions of Rontgen's work what are only direct and obvious consequences, perceived by himself, of the facts which he has observed. ANDREW GRAY.

University College of North Wales, Bangor, March 1.

In your last issue (p. 399), in the account of the work appearing in the Comptes rendus, you state that M. de Heen "proves Conclusively that the X-rays proceed from the anode and not the kathode." May I point out (as I did at the Royal Society, in the course of the discussion on Prof. J. J. Thomson's paper, February 13), that I have proved that this is undoubtedly true for the bulb that I have been using throughout my experiments on the X-radiation. The bulb is one in which the negative electrode is concave, and the negative stream is thereby focussed to a point on the anode, which is a platinum disc placed near the centre of the bulb. By measuring the positions of different parts of a radiograph of a series of concentric zones of tinfoil placed in a measured position, I have shown that the actinic rays diverge from the anode disc.

I am of opinion, however, that in this respect this bulb differs A translation of Prof. Salvioni's paper will be found in another part of this issue.-ED. NATURE.

from those which have been employed by others. In these latter, judging from the published accounts, the negative stream impinges directly on the glass; and for bulbs of this kind, it has been shown conclusively by Prof. J. J. Thomson that the seat of the origin of the rays is the glass itself. The proof is that a sensitive plate placed inside the bulb in the path of the negative stream is not acted upon. I venture to think that, in the case of my bulb, a sensitive plate placed inside would be acted upon provided it lay in the hemisphere of the bulb in which the kathode lies. I intend to test this conjecture experimentally. Should it prove true, the behaviour of both varieties of bulb will probably be capable of description by the following single state

ment:

The seat of the origin of the X-rays is where the negative stream first impinges against a solid, and gives up, or partially gives up, its negative charge. ALFRED W. PORTER.

University College, London, February 28.

IN

66 your Notes" of last week you refer to a communication of M. de Heen, stating that the X-rays proceed from the anode. Some experiments, which I made at the beginning of last month, bearing on this point, may be of interest to your readers. It is of course not the case that the X-rays proceed from the anode in general, but they may be made to do so by placing a small disc as anode facing the kathode. The kathode streams impinge on the former, and the X-rays being generated there radiate from it. The experiment was made by placing a lead plate (4 cm. by 10 cm.), with a rough circular hole in it, at a distance of 10 cm. above the photographic plate, and the tube (a small one with a curved kathode facing a small disc anode) 10'5 cm. above the lead. After development the negative was replaced exactly in its former position. Several interesting facts showed themselves, the most striking being that the image of the hole consisted of a well-defined circle showing even individual splinters on the edge, and in addition diffused elongation on two sides. On placing the eye so that the hole exactly covered its well-defined image, it was necessary to put it in the position occupied by the anode.

The diffused images in the same way were seen to be due to the fluorescent parts of the glass sides of the tube-a kind of pin-hole photograph, in fact.

The rays leave the anode as if they were the splash of a jet of water occupying the position of the kathode stream. In other words-supposing the plane of the anode vertical and the kathode to the right, then no rays appear to the left of the plane of the anode, whilst on the right the space is exceedingly rich, The negatives show, in every case tried, two well-defined regions, viz. nothing to the left of the intersection of the plane of the anode with the negative, and a dense deposit on the right, the richest part apparently being close to this line. It is difficult to account for this on the supposition that the rays are due to waves generated at the point of impact. We should expect in this case the action on the plate to increase with the visual angle of the anode disc as seen from points on the plate. On the other hand, certain further experiments seem to show that the action is not in all respects similar to the splash of a jet. Whether the effect is due to the fact that the place of impact of the kathode stream is an anode, or simply an internal obstacle, I have not yet determined, but experiments in progress will, I hope, settle this point.

For photographic purposes, the best kinds of tube are those with a curved kathode converging the streams on a small plane anode, remembering, of course, that the strong field is on the kathode side of the anode plane. This behaves very approxim ately as a radiating point. With this I have obtained, with comparatively short exposures, and a 24" to 3" spark length, strong negatives of remarkable definition, certainly finer than any I have yet seen.

Firth College, March 1.

W. M. HICKS.

I WAS interested to see in your last issue a letter from Mr. Swinton describing his reproduction of Prof. Salvioni's experiments with phosphorescent screens. Mr. Swinton uses a piece of blotting paper impregnated with platino-cyanide of barium. I have tried this method, but have obtained better results with a screen prepared with the same salt, as follows:

A piece of fairly stout black paper, free from pinholes, is coated with gum containing a little glycerine, and, as soon as it has