metres. No theoretical explanation of the observed receptive range of short wave signals is as yet forthcoming; it is only obvious that the Austin formula for adsorption does not apply to short wave phenomena.

An invention likely to become familiar in the course of a few months is the Fonofilm system of talking pictures due to De Forest of thermionic valve fame. In this process the sounds, e.g., of orchestra, voice, or musical instrument, are recorded as a series of fine lines at the edge of a standard cinematograph film. To reproduce the sounds a beam of light is passed through this edge on to a thalofide screen. The variations in the intensity of the light due to the fine lines cause corresponding variations in the electrical resistance of the thalofide and these variations magnified by a battery of valve amplifiers cause the original sounds to be emitted by a loud speaker. The details of the process have not been revealed but its success is beyond question, and, running costs permitting, the reproduction is good enough for presentation to the public in the ordinary cinema hall.

The Admiralty permitted publication of the details of new methods of depth sounding and position finding developed by the Scientific Research Department under the direction of Mr. F. E. Smith. The depth sounder is a particularly ingenious device. A diaphragm let into the side of the ship is struck every half second by a small hammer whose movement is controlled electrically. The impulse so produced travels down to the bed of the sea, is reflected and received by a hydrophone also let into the side of the ship. The observer receives the sound from the hydrophone in a telephone whose terminals are short-circuited except at certain definite moments when they are connected to the hydrophone. These instants of connexion to the hydrophone occur every half second and at a variable but known period after the hammer has struck the diaphragm. This period is adjusted, by moving a pointer over a graduated disc, so that the impulses reflected from the sea bed are heard in the telephone. The period is, of course, that taken by the sound to travel twice the depth of the water. The velocity of sound in sea-water having been determined (with the same apparatus) the desired depth immediately follows.

Turning next to the domain of pure science and dealing first with astronomy, we have to record as the outstanding feature of the year Eddington's work on the relation between the masses and luminosities of the stars. Eddington's discovery was that the luminosity of a star is very approximately a function of its mass alone. He obtained this result theoretically by assuming that the material of a star behaves as a perfect gas; but when put to the test it was found that nearly all the stars behave in the same way even though their density far exceeds that of water. An explanation of this last result is provided by supposing that, at the high temperatures which obtain in the interior of the stars, the atoms are stripped of most, if not of all, their orbital electrons and have, in consequence, only about one hundred thousandth part of their normal bulk. Eddington's result implies that the dwarf stars have a smaller mass than the giants-a result to be expected from relativity principles if they represent different stages of evolution. According to

the relativity theory loss of energy implies a corresponding decrease of mass (to be precise the energy lost is equal to the decrease of mass multiplied by the square of the velocity of light) so that, for example, the sun in consequence of its radiation must be losing mass at the rate of four million tons every second. Thus as time goes on the energy radiated by a star and its mass both gradually decrease.

Important consequences follow from Eddington's theorem, for hitherto all calculations in cosmogony have been based on the assumption that the mass of a star remains constant. The time scale is increased and the continual decrease of mass implies a corresponding expansion of the universe which, in past ages must have been much more closely packed than now. The close packing and increased time disturbs the attractive conclusion deduced by Jeans from his tidal theory of the formation of the solar system, namely, that the earth is quite possibly unique in all the universe.

Jean's theory that normal low density stars are being formed by condensations in the arms of spiral nebulæ, was opposed by Professor Shapley of Harvard whose calculations led him to conclude, that stars so formed would be of the wrong order of absolute magnitude. Shapley's observations of the variable stars in globular clusters have shown that the velocities of blue and of yellow light in stellar space do not differ by as much as one part in twenty thousand millions.

In experimental physics a good deal of interesting work has been done. During the summer Michelson obtained a series of observations with his new velocity of light apparatus which employs a revolving octagonal mirror. Working over a distance of 22 miles from Mt. Wilson Observatory to Mt. San Antonio, he finds the velocity to come out as 299,820 kilometres per second with an uncertainty of 1 part in 10,000. The best previous experiments were those of Newcomb which gave 299,860 kilometres per second with about the same probable error. Michelson proposes to repeat the observations next summer with improvements suggested by the preliminary work and hopes to reduce the uncertainty in his measurements to 1 part in 50,000.

Two methods for the production of intense momentary magnetic fields have been described during the year. In the Proceedings of the Royal Society for June, P. L. Kapitza, writing from the Cavendish Laboratory, Cambridge, describes how he has obtained magnetic fields whose intensity exceeds half a million gausses and indicates the possibility of obtaining fields four or five times greater. F. T. Wall, working at Sheffield University, by a different method has obtained fields up to about 1.5 million gausses and anticipates reaching 10 millions. These fields are produced by the momentary passage of very large currents through solenoid coils of small diameter. In Kapitza's experiments the necessary energy is stored in lead plate accumulators so arranged, that they can be suddenly discharged in a hundredth part of a second at some 10,000 amperes by a specially designed switch. Wall uses electrostatic storage in a battery of condensers whereby oscillating currents are obtained, the peak values being of the order of 25,000 amperes. Kapitza has applied his fields to a-ray tracks and to the Zeeman effect; Wall to the magnetic behaviour of steel. His work received a good deal of

publicity during the year by being represented as an attempt to explode the atom.

The problem of the transformation of the elements continues to excite an active interest. Rutherford has effected the transformation in the case of certain light elements, by bombarding them with swift a-particles. It now seems possible that gold has been obtained from mercury, both by Miethe in a Jaenicke mercury lamp burning overcharged and at the Institute of Physical and Chemical Research, Tokio, where a visible crystal of gold is reported to have been obtained.

Dr. F. W. Aston has continued his work on isotopes with his Mass Spectrograph. His investigations on the elements of the alkaline and rare earths have been particularly fruitful and show that both strontium and barium have isotopes whose atomic weights are quite definitely less than whole numbers. In the case of tellurium, the observations indicate that there are three isotopes whose masses fall short of whole numbers by one or two parts in a thousand. The results obtained by Dr. Aston in the case of this element tend to show that its atomic weight is greater than 128; the latest chemical determinations give 127·5.

There have been no new developments of the Bohr theory which need to be recorded. Millikan states that he has obtained certain results which are in conflict with the theory in its present form, but it is so flexible that, without doubt, an explanation will, in due course, be forthcoming. The problem of reconciling the quantum hypothesis with the phenomena of interference remains unsolved; a suggestive paper by de Broglie may prove of assistance in its solution.

A discussion before Section A of the British Association focussed attention on the divergent views of Professor A. N. Compton of Chicago, and Professor Duane of Harvard concerning the mechanism of the process of the scattering of X-rays by material substances. Compton's work supports a theory put forward independently by himself and by Professor Debye of Zurich. It supposes that, when a quantum of radiation falls on the scattering substance it may be considered as colliding with an electron which is either free or very loosely bound to the atom. This electron takes some of the energy of the quantum and the radiation passes on as a quantum of radiation of diminished frequency. Assuming that, for the encounter, the laws of the conservation of energy and momentum hold good, it is found that the wave-length of the scattered radiation should depend on the angle through which its path has been turned as a result of the impact. Compton and several other independent observers have verified this experimentally. Duane on the other hand obtains results which confirm another explanation of the scattering based only on the Einstein energy equation. There is at present no satisfactory explanation of these very different results.

Another controversy has arisen between Professor Vegard and Professor McLennan concerning the luminescence of solid nitrogen and its bearing on the auroral spectrum. Solid nitrogen when bombarded by cathode rays gives a spectrum of rather an unusual type. It shows in particular a band in the green with three maxima which McLennan regards as ordinary spectral lines. Vegard, however, states that they have no definite positions and considers that the green line of the auroral spectrum

represents the limiting position of this band when the luminescent particles are reduced to a molecular order of magnitude. This difference of opinion first became manifest at the Fourth International Congress of Refrigeration already referred to. Two other interesting results were revealed at this Congress. First, that experiments on liquid helium show that it has a maximum density at -270-8° C.; secondly, that all metals do not become super-conductors at very low temperatures, but only those possessing an electron (or electrons) which can respond far more readily than the rest of the atom to the magnetic field and whose orbital motion is free from interference by the other electrons. That the phenomena of super-conduction is different from that previously supposed is shown by the fact that currents induced in a ring of super-conducting metal persist when the ring is cut so that the circuit is no longer closed.

In physical chemistry much work has been done on the conditions which determine chemical activity, but the conclusions reached are as yet very indefinite.

The Report on the work of the Department of Scientific and Industrial Research for 1923-24 shows that nine Research Associations have reached or are about to reach the end of the five year period during which grantsin-aid were promised by the Department. The work of these associations has been reviewed by suitably constituted committees, and only in one case has their report on the scientific results achieved been unfavourable, namely, in the case of the Glass Research Association. For this and other reasons the provision of another method of providing for glass research is under consideration. In the case of the British Portland Cement Association the subscriptions now being raised by the industry itself are sufficient to provide for effective research.

ART, DRAMA, CINEMA, AND MUSIC.

I. ART.

THE year 1924 was remarkable for three things-the exhibition in the Palace of Art at Wembley of a large collection of works by British artists past and present; the coming of age of that invaluable institution, the National Art Collections Fund; and the centenary of the National Gallery. The original National Gallery, the hundredth anniversary of whose establishment was celebrated in April, contained only the collection of pictures formed by John Julius Angerstein, which were purchased by the Government in 1824 and at first exhibited at No. 100 Pall Mall, the house formerly occupied by Angerstein. The purchase of the pictures, strongly urged by Lawrence and others prominently connected with the arts, was regarded as an important event; and the opening of what was the first public picture gallery in England had been awaited with interest and curiosity. Yet for some reason the opening ceremony on the 10th of May, 1824, was almost ignored by the principal contemporary newspapers, none of which described the building or the pictures it contained or said anything about the people who were present. Times recorded the event in a paragraph of half a dozen lines, the Morning Post gave it the same amount of space, and the Morning Chronicle neglected it altogether.

The

Angerstein's house in Pall Mall has long since disappeared, and except for a drawing or two there is no record remaining of the original National Gallery. But those who were invited to the reception at Trafalgar Square, held in April, to mark the centenary, were able, owing to a happy idea on the part of the authorities, to obtain some idea of the quality of the pictures shown in 1824. A number of them, including many not now exhibited, were arranged in one room, and the result was interesting but not altogether impressive.

In October the National Gallery was enriched by the Mond pictures, which were placed on view in that month in Room XXVI. Collected by the late Dr. Ludwig Mond they were left by him to the National Gallery subject to the life interest of his widow, who died in 1923. The Mond pictures are perhaps the most valuable gift ever made to the National Gallery, and include a Crucifixion by Raphael, a fine early work of large size; works by other Italian masters (Crivelli, Botticelli, and Bellini), and a Murillo, "St. John in the Desert," which is of great interest because of its connexion with a famous English painter. It was brought from Spain by Richard Cumberland and bought by Gainsborough for what was then considered the high price of 5001. Several other pictures were acquired by the Gallery during the year, including a