time, in a new and forcible way, important questions of electrical theory, and the physiological effects of rapidly alternating currents. That he should have been able unharmed to place himself in the space between two tinfoil plates connected to the terminals of his rapidly alternating machine, was to the ordinary observer in itself sufficiently startling; but that he should have been able to present a piece of iron to one of the poles of the machine, drawing a spark of several inches in length with impunity, and thereby to interpose his body as a connecting link between the machine and a long vacuum tube which glowed like a flaming sword, must have appeared to many of those most conversant with electrical phenomena truly astonishing.

Hitherto, alternating machines of great frequency and high potential have been deemed peculiarly dangerous, and not without reason. But it did not follow, of course, that with a sufficient increase of the frequency of alternation, the danger might not completely disappear. It will be of great importance to inquire in what way the immunity of the experimenter from injury is brought about. Are impulses of 20,000 reversals per second and upwards without serious effect on the nervous system of the human body, so that conduction takes place through it without any disagreeable consequences? or is the conduction effected without the nervous system being concerned at all?

The delicate network of nerves in the eye is sensitive to a certain range of frequency of electrical vibrations, and perfectly insensitive to vibrations which lie outside that range in frequency. In the same way the insensitiveness of the general nerve-system of the human body interposed between a glowing vacuum tube and the terminal of a rapidly alternating machine or transformer may begin and end at much lower limits. There is also, of course, the interesting question of the distribution of these rapidly alternating currents in the somewhat complicated conductor formed by the human body, which may have a great deal to do with the result.

It ought to be recalled here that Prof. J. J. Thomson has been working in the same field, and has obtained somewhat similar results. These were made the subject of a very interesting demonstration to the members of the Physical Society on the occasion of their visit to Cambridge in May of last year. For a long time Prof. Thomson has investigated this subject both theoretically and experimentally, and his researches have thrown much light on the rationale of the very striking results obtained by Mr. Tesla and himself in their closely allied but independently carried out series of experiments.

The admirable experiments of Mr. Tesla are only another instance of the way in which practical applications of science promote its progress, by enabling apparatus to be constructed on an engineering scale, and with all the security for effective action which the constructive art of the engineer furnishes so well. His simple alternating machine, running with very little clearance at a speed of about 2000 revolutions per minute, is itself a triumph of skill in design and construction, and well illustrates how desirable and even necessary it is to take advantage of all the aids to exactness, and they are many, which can be obtained from the refined machine tools and truth of design which characterize the engineering workshop of to-day. The ordinary optician of twenty years ago, with his imperfect lathes, and general utter want of power-driven appliances, his continual handfitting and shaping, and the absolute non-interchangeability of the parts of his instruments, has almost passed away; and even the physical laboratory has become in great measure an engineering workshop, in which are to be found Whitworth lathes and end-measuring machines adapted for the most exact work.

One point in this connection is worthy of notice. Mr. Tesla insists strongly on the essentially electrostatic

nature of the phenomena illustrated by his lectures; while, on the other hand, one object aimed at in Prof. Thomson's experiments was to show that in a tube without electrodes luminosity could be produced by electrodynamic action alone-that is to say, in a field of electric force which is not electrostatic in the sense of admitting of the derivation of its intensity at each point from a potential function.

The changes produced in the distribution of electricity on neighbouring conductors will cause glow in a vacuum tube when a Holtz machine or Leyden jar is discharged; and this will in general be more or less operative. But it is not in general possible to separate the electromotive forces due to this cause from those due to electromagnetic action. Prof. Thomson has succeeded in some cases in screening off these electrostatic effects, and in producing a glow discharge in which electrostatic action could have little or no share.

The glow or flame discharges from the terminals of his induction coils, the glow discharge from the long wires stretched from the induction coil towards the roof of the hall, the glowing vacuous bulbs and phosphorescent tubes placed in the field between the parallel tin-foil plates attached to the transformer terminals are all phenomena of the highest importance; though, of course, they are only exceedingly striking and effective illustrations of experimental results already arrived at by the lecturer himself and others, and communicated in a more or less complete manner to the electrical world. The application of these, which Mr. Tesla suggests as a possible one in the future, would bring about an ideal form of electric lighting, which would transcend in luxury and convenience our present system of electric lighting by incandescent lamps as far as the latter transcends the oil lamps and tallow dips used by our near ancestors. Every drawing-room would become an electric field in a continual state of rapidly alternating stress, in which the occupants would live, experiencing no unpleasant effects whatever, while vacuous bulbs or phosphorescent globes and tubes, without care or attention, would shed a soft diffused light, of colour and intensity arranged to suit the most luxurious fancy. It would be interesting also to know whether, after all, habitual dwelling in a region of electric stress rapidly changed from one extreme of high intensity to the opposite, produced very slow physiological effects which could be traced in the improved health and longevity of the persons so dwelling, or the reverse. If such applications are made (and there does not seem to be any sufficient reason why they should not come to pass), the magnificent researches of Mr Crookes, as well as those of other investigators to whom the lecturer justly and generously acknowledged his indebtedness, will bear some practical fruit in an almost totally unexpected manner, by becoming at once available in connection with a new and beautiful development of what is at present the most progressive of the physical sciences. It does seem that we are on the point of farther great advance into the undiscovered domain of electrical science, and it is significant that it is likely to lie along one of the routes made clearer to us by the discovery and verification of the great theory of electrical radiation. Who knows what further discoveries may be obtained before the present century has come to an end? We are advancing so rapidly that no one can declare that the record of discovery of the nineteenth century has nearly closed. One important means of further investigating electrical radiation will be that which Prof. Fitzgerald made an attempt to find-a means of maintaining for any required length of time electrical vibrations of sufficiently high frequency. Mr. Tesla's results seem to promise that this problem may perhaps be solved before very long, and many outstanding questions of the electromagnetic theory of light thereby set at rest. In many other ways his researches are certain to promote scientific

cluded its general adoption for class purposes. It struck me that it ought to be possible to draw a series of eccentric circles upon a disk in such a way that, when rotated, the motion of the intercepted lines, as seen through a narrow radial slit, should correctly represent this motion. This, of course, is done for progressive waves by Crova's disk. After spending some thought upon the matter I succeeded in producing such a disk, a copy of which I inclose. It has given such satisfaction that I have been advised by several scientific friends to send a description of the method to you for publication, for the benefit of teachers and students generally.

In the following description I have given the dimensions which I myself employ in describing these disks, but they can of course be varied at will:

A piece of stout cardboard should be taken about a

points 1, 2, 3 ... 13, 12, 11, 10, 9, 8, 7 successively as centres, a series of circles should then be drawn beginning with a radius of 1 inch, and increasing it each time by inch. The last circle therefore, described with the point 7 as centre, has a radius of 4 inch. The two circles described with the point 7 as centre, since they represent nodes, should be drawn rather thicker than the others to distinguish them.

The disk is now complete. It should be cut circular in shape and mounted to rotate upon a pin struck through the point 7. If it now be examined by means of a narrow radial slit extending across the marked portion of the disk, the short lines intercepted will, by their pendulum-like motions, represent the motion of the air particles in a closed organ pipe giving its first overtone. When the slit is shortened so as to show only the portion of the

disk between the two nodal lines, the vibration of a rod clamped at both ends will be represented; whilst the outer half of the latter length of slit will represent similarly a closed organ pipe giving its fundamental note. In this way by restricting the slit to various parts of the disk, various vibrating rods of metal and organ-pipes can be represented.

The disks thus produced I have had very satisfactorily lithographed for students' use.

Should any of your readers be desirous of obtaining further information I shall be happy to oblige them. F. CHESHIRE.

P.S.-In the drawing of the disk given the centre has been filled up by broken circles. As thus drawn the inner circle may with advantage be blackened over.

THE SCIENCE MUSEUM AND GALLERY OF BRITISH ART AT SOUTH KENSINGTON.

MOST people were under the impression that they had heard the last of the absurd proposal that the site in South Kensington, which had already been set apart for scientific purposes, should be appropriated for the British Art Gallery. After all, however, the scheme has not, it seems, been definitely abandoned. Mr. Tate is said to have decided that if this particular piece of land is not granted he will withdraw the offer of his pictures and of the money he is willing to give for the erection of a suitable building. Men of science, like other people, would be sorry if the nation lost the advantages which Mr. Tate wishes to confer upon it; but they are bound to protest strenuously against the notion that it is either right or expedient to try to promote the interests of art at the expense of those of science. The South Kensington site is urgently wanted for the purposes for which it has been promised. Careful investigation has shown that every foot of the land will be needed for an adequate Science Museum and for laboratories; and if Mr. Tate's idea is acted upon, irreparable injury will be done, not only to the Royal College of Science, but to the entire system of scientific training in England. It has been asserted that the land" was bought for science and art," and that, consequently, science has "no monopoly in it." The land was not bought for "science and art." It was bought for "science and the arts," by which were meant the industrial arts, the development of which directly depends on science. The whole difficulty is due to the haphazard way in which all that relates to science is treated by public authorities in this country. If England had possessed a Minister of Education, with powers corresponding to those which belong to the French or the Prussian Minister of Education, he would never have permitted this question to be even opened; and Mr. Tate would probably have obtained long ago a proper site elsewhere. Of course nothing that can be done to prevent an act of utter folly and injustice will be left undone in Parliament by the scientific members.

The following letter on the subject appeared in the Pall Mall Gazette on Wednesday, February 10:—

SIR, Before Parliament and the public agree to the somewhat exacting terms which Mr. Tate appears to make a condition of his munificent donation, I would beg your leave to submit the following questions for their consideration :

1. Why should he not be satisfied with the plot of ground, somewhat higher up the Exhibition Road, which is much larger than his contribution of £80,000 will cover with a decentlyconstructed building? The situation of that plot is in every respect better than the one he covets. It is adjacent to the East and West Galleries, which are already connected by a cross gallery. These galleries are, in the opinion of the most eminent artists in the country, the best galleries for the exhibition of pictures yet constructed in England, and in them the overflow from Mr. Tate's gallery might in future time find a home.

2. Why should the site which he asks for be cleared of the

Physical Laboratory and other portions of the College of Science already housed on it to interpolate an English Luxembourg between two portions of the Science School and Science Museum, relegating the latter to the aforesaid admirable picture galleries, which then for all time can never be annexed to the Tate Gallery, or even put in connection with it? Why, in fact, should the science instruction of the country be sacrificed to this collection of pictures, which is not of sufficient value to be accepted by the National Gallery? We hear a good deal of the French Luxembourg, but would any munificent donor of modern French pictures be allowed to have a slice out of the middle of the École Polytechnique, or of the École Centrale, or of the Conservatoire des Arts et Métiers, if, peradventure, that was the Naboth's vineyard which his heart craved for?

3. Why should the Government or the public suppose that if Mr. Tate's collection of pictures were inserted like a seton into the tissue of the College of Science it would have the effect of drawing a shower of gifts and bequests away from the rival establishment across the Exhibition Road, and only separated from it by a part of the College of Science? That rival establishment contains the Sheepshanks collection, given under stringent conditions to found, and accepted by the Government to found, a National Gallery of British Art. Other collections have been added-even since the Tate Gallery was in the airon the same conditions. Intrinsically and artistically they are worth probably ten times as much as the Tate collection. From the recent competition which has been held it is evident that the Government propose to spend a large sum of money in completing the South Kensington Museum, which will then be in a position to properly they cannot be sent to the Tate Gallery. exhibit these and other bequests. lost to the nation if an attempt were made to do so, the pious They would be donors having taken ample precautions against such tricks being played with their gifts. Whatever pranks the Royal Academy may play with the Chantrey Bequest, there is no reason to suppose that the British Museum or National Gallery pictures can be sent to increase the importance of this new establishment under an irresponsible management, which is not supported by a single artist of eminence, as far as I am aware.

It is well known that

4. Why should Government emulate the antics of the celebrated cow who kicked over the pail of milk she had just filled, and, having done more than any previous Government for technical instruction, make itself superbly ridiculous by dealing an irremediable blow to the advance of that instruction for the sake of Mr. Tate's £80,000? It must be remembered that there is no institution for the advancement of scientific instruction in the country similar to the College of Science with the Science Museum which it is now proposed to dismember for the sake of that £80,000.-I am, Sir, yours obediently, London, February 9.

NOTES.

THE late Prince Louis Lucien Bonaparte has left to the Nation his valuable collection of metals, which is now in course of arrangement at the Science Museum, South Kensington. The collection is rich in specimens of the rarer metals. This bequest is the result of a promise made to Prof. Roberts-Austen, the Prince having been much interested in the Percy collection at South Kensington. The Prince's early papers, which were mainly chemical, comprised an account of a method of separating cerium from didymium; and he used to refer with pride to his having won admission to the ranks of the Legion of Honour by chemical research.

In order to afford increased and improved accommodation for the departments of physics and mechanical and electrical engineering, the Council of University College, London, have decided to enter without delay upon a considerable extension of the College buildings. The addition to the College will form an important block opposite the east end of University Street, with an extension for some distance along the Gower Street front of the College grounds. It is to contain separate laboratories and lecture-rooms for mechanical engineering and electrical engineering, with rooms for engineering drawing, a

dynamo-room, and all else that is required for an efficient school of modern engineering. This extension will enable the basement and ground-floor of the central wing of the main building, together with a new building to be erected in the inner court, to be devoted to the department of physics, which has hitherto been very imperfectly provided for in rooms that were originally intended for quite other purposes than those to which they have been applied. The position of the new physical laboratory is such that it will be as far removed as is easily possible, in the heart of London, from heavy street traffic.

THE death of the well-known botanical collector, B. Balansa, is recorded in the French journals. He died in the military hospital of Hanoi, Tongking, to which country he went on a second botanical expedition. Balansa was not merely a collector of plants; he was also a botanist, though he never published much, his principal contributions to botanical literafere being on the grasses of New Caledonia and of Cochin China. He also published a botanical account of his ascent of Mount Humboldt in New Caledonia. But as a botanical collector, Mr. Balansa contributed to nearly all of the principal herbaria of Europe, having spent many years of his life collectng in Algeria, Morocco, Asia Minor, New Caledonia, Paraguay, Tongking, and other parts of the world. On Sir Joseph Hooker's

recommendation he was attached as botanist to the Commission appointed in 1873 by the Paraguayan Government for the scientific exploration of its territory; and he spent three years and a half traversing the country in various directions for this purpose. He made very large botanical collections, but these, s well as his New Caledonian plants, have only been partially worked out. Kew purchased a set of about 2000 species.

ON Saturday last the members of a mountaineering and scientific expedition, under the leadership of Mr. W. M. Conway, sailed by the steamship Ocampo for Karachi, whence they will proceed, by way of Abbotabad and Kashmir, to the mountains of Baltistan, on the frontier of Eastern Turkistan. Their object is to explore thoroughly the high glacial area of the Karakoram range. One of their chief aims will be to make a special survey of the great Baltoro glacier, which descends from the peak K 2" (28,265 feet), the second highest measured peak the world. They will make scientific collections, and record ebservations of glacial phenomena. The Baltoro, Punmar, and Bafo glaciers, which unite their streams in the neighbourhood of Askoley, are believed to be the largest glaciers in the world catside of the Arctic and Antarctic regions, and their upper levels have never yet been explored. Mr. Conway is accompanied by the Hon. C. G. Bruce and Mr. J. H. Roundebush; and they are taking with them Mr. A. D. McCormick, artist of the expedition; Mr. Oscar Eckenstein, a well-known Alpine climber; and Mathias Lurbriggen, of Macugnaga, one of the famous family of Alpine guides. It is understood that they intend to make a determined assault upon "K 2," or one of the loftiest of the neighbouring peaks, with a view to discovering whether the limit to which qualified mountaineers can chimb has yet been attained. The expedition, it may be mentioned, has been subsidized both by the Royal Society and by the Royal Geographical Society.

the

A CRIMEAN Alpine Club has been formed at Odessa. The objects of the members are to explore the mountains of the Crimea, to publish scientific papers on phenomena connected with them, to protect rare species of plants and animals, to favour the development of agriculture, horticulture, and small local industries among the mountaineers, and to provide facilities for tourists, artists, and men of science who may desire to visit the region.

THE 1892 Photographic Conference will be held at the Society of Arts on Tuesday and Wednesday, March 22 and 23, under the presidency of Captain W. de W. Abney, F.R.S.

LAST week we mentioned the case of the miner Johann Latus, of Myslovitz, in Silesia, who had been asleep for over four months. The latest news about him is that he has partly recovered, and the cataleptic rigidity of the limbs, which was characteristic of his somnolent condition, has disappeared. It is curious to note that, although he has conversed with his wife, he seems quite unaware of the long stay he has made in the hospital. No feeling of pain of any sort has been experienced by him, and in fact he cannot recall any sensation during this long period. Dr. Albers, who is attending to him, hopes that he will soon completely recover. Unfortunately Latus has been threatened with inflammation of the lungs, which, view of his present weak state, might be fatal to him. He still continues to take only milk diet, having refused both meat and wine.

sinia.

DR. G. SCHWEINFURTH has taken up his abode in the Italian colony on the Red Sea for the purpose of completing his investigation of the flora of Yemen and of Northern Abys He is accompanied by Dr. D. Riva, of Bologna. PROF. L. H. BAILEY has been appointed special agent of the United States Weather Bureau for the purpose of making a report on phenology, and the relation of climate to the times of blooming, fruiting, and leafing of plants.

MR. WORTHINGTON G. SMITH reports that he has now made water-colour drawings of 492 species of British Basidiomycetes, including the whole of the white-spored species of Agaricus, for the public gallery in the Botanical Department of the British Museum. The total number of British Basidiomycetes is over 2000, and these are intended to be completed on

96 sheets. Closely-allied species are placed side by side, so

that the salient points of differentiation can be seen at a glance. THE fourth number of the Journal of the Leprosy Investigation Committee, just issued, presents much information on leprosy in Russia, Brazil, and Madeira. It contains also papers on the communicability of leprosy by vaccination, and various notes and abstracts. We learn from the Journal that the Report of the Leprosy Commission, together with an appendix containing the results of their laboratory work, is being printed in India, and will probably be ready for issue from the office of the National Leprosy Fund, in London, in a very few weeks.

THE people of Vienna have been greatly alarmed by the outbreak of a new epidemic, which is believed by some to be connected with the influenza. It affects the intestines, its symp toms being fever and acute colic, with the ejection of blood. Its appearance seems to indicate the absorption of some poisonous matter. At first it was attributed to the drinkingwater, but this view has been generally abandoned. A representative of a Vienna newspaper has taken the opinion of some of the leading Vienna physicians on the subject. Prof. Nothnagel hesitated to pronounce any judgment on the nature of the illness, the facts not having been sufficiently studied. Prof. Drasche thought it might be "nothing else than a distinct form of influenza," and was confident that it was not due to the drinking-water. Prof. Oser was also sure that the drinking-water had nothing to do with the disease, and "did not consider that there was any indisputable evidence of its connection with influenza." Dr. Bettelheim seemed to think that there was something in common between influenza and the new malady called "catarrh of the intestines." He based his opinion on the fact that from the day when the latter made its appearance in an epidemic form cases of ordinary influenza had begun to decrease. He looked upon them both as being of an infectious nature. A chemical analyst, Dr. Jolles, said it would require three weeks to make a bacteriological inquiry into the character of the illness. A chemical analysis of the drinkingwater showed it to be of normal purity.