undertaking never to interfere with Fiume politics again. He then took refuge in Croatia, more or less under Yugoslav protection, but continued to regard himself as the sole 'legitimate' representative of Fiume, and even tried to obtain recognition from the League of Nations. The government of the town passed from one committee to another, until the Italian Government insisted on re-summoning the Constituent Assembly; but the majority of that body still supported Zanella and quitted Fiume to meet in Yugoslav territory, where it lapsed into obscurity. The minority formed a new administration under Signor Depoli. But he had constantly to apply to Italy for financial support, owing to the conditions of the town, and there was always an Italian garrison for the maintenance of order. The various difficulties connected with the execution of the Rapallo Treaty led to further negotiations at Santa Margherita in May 1922, and a new agreement was signed in October following. It provided that the arbitration clause should be extended to divergences concerning the mixed port committee and the operation of the port, that Yugoslavia should reopen railway communications with Fiume (the Yugoslav authorities had cut the railway at Sushak ever since the D'Annunzio adventure), for the creation of a mixed commission to settle the constitution of Fiume and of a neutral customs zone round Zara, and for guarantees for the Italian schools in Dalmatia. But even Santa Margherita did not solve the Adriatic problem, and the conditions of Fiume became worse every day. In November 1922, the Fascista Government came into power in Italy. The Yugoslavs at first feared that this change would involve a less friendly attitude towards them, but events belied their alarm. Signor Mussolini, in fact, in one of his first speeches declared that the Santa Margherita agreement must be ratified, but at the same time he realised the extreme difficulty of carrying out that convention and the Rapallo Treaty as they stood, and as early as November 1922, he suggested to M. Ninchich, Yugoslav Foreign Minister, then at Lausanne for the Turkish Treaty, the possibility of a solution such as the one now adopted. Feeling on both sides had distinctly improved, the Santa Margherita This series of agreements, to be followed by a commercial treaty, should at last establish Italo-Yugoslav relations on a sound friendly basis and put an end to the six years' wrangle and to old misunderstandings derived from the fatal Austro-Hungarian heritage, provided, of course, that they are loyally carried out on both sides. Italy had renounced Dalmatia by the Rapallo Treaty, which in this connexion remains in force, and thereby loses the Italian communities in that province. The loss is hard to bear, but Yugoslavia renounces all claims to the much more numerous but less civilised Slav communities in the Venezia Giulia. Italy has always shown herself generous towards her alien subjects-Signor Mussolini is particularly firm on this point-and Yugoslavia has now every interest in abandoning the Balkan tradition of intolerance, at least so far as the Italians of Dalmatia are concerned. As for Fiume, the 'passionate city,' it has everything to gain by the new arrangement, for it can now at last hope to see normal conditions of existence re-established. As a free State it would have had no real vitality, and would have been, as Signor Mussolini pointed out in his above-quoted report, the platform of endless intrigue and party squabbles. Now, in accordance with the essential sentiments of the inhabitants, it is an Italian city; but its trade will be international. It must not be expected that its pre-war prosperity will return; Hungary is much reduced in size and wealth, and the trade of her lost provinces will tend to flow down other channels. But Fiume's natural advantages and excellent port and railway facilities should attract to it a fair share of its old trade, especially that between Hungary and the Mediterranean and between Italy and Yugoslavia and other Balkan lands. The treaty of friendship may have even more farreaching consequences, for it should not only avert the danger of an Italo-Yugoslav conflict, but, in spite of the above-quoted additional protocol, should also contribute to detach Yugoslavia from the general scheme of militarist alliances in Central and South-Eastern Europe and of aggressive plans, which have threatened the peace of the world since the Armistice. Art. 5.-THE ATOM. 1. Conduction of Electricity through Gases. By Sir J. J. Thomson. Cambridge University Press, 1903. 2. Radioactive Substances and their Radiations. By Sir Ernest Rutherford. Cambridge University Press, 1913. 3. Atomic Structure and Spectral Lines. By Dr Arnold Sommerfeld. Methuen, 1923. 4. The Theory of Spectra and Atomic Constitution. By Dr Niels Bohr. Cambridge University Press, 1922. 5. Die Radioaktivität. By Dr S. Meyer and Dr E. v. Schweidler. Leipzig: Teubner, 1916. 6. Isotopes. By Dr F. W. Aston. Cambridge University Press, 1922. 7. The Structure of the Atom. By Dr E. N. da C. Andrade. Bell, 1923. 8. The Structure of the Atom. By Dr N. R. Campbell. Cambridge University Press, 1923. It is curious perhaps that the most vigorous and imaginative minds in physics and chemistry to-day should be concerned with the most insignificant thing in Nature, the atom. But the reason of this is partly the fact that knowledge of the structure of the atom and its workings is knowledge of a fundamental kind in science, and partly that the subject is now at such a stage of development as to possess an interest and a charm that are almost irresistible. Knowledge of the workings of the atom is a new thing; it is mostly the product of the research of the past twenty-five years. It is the product of what Sir Ernest Rutherford has called, not inaptly, the Heroic Age in physics, a period that had its beginning last century in the middle of the so-called decadent 'nineties. Of course there are no abrupt changes in science; the scientific method is always at work penetrating however short a distance in a given time the dense mist of ignorance that envelops mankind. But from time to time there arises an illuminating idea, a deduction from accumulated knowledge that is obvious when it is expressed, which leads to a special advance, and to a renewal of the attack on ignorance with greater effort and on a wider front. These are the times to live in, if one is a worker in science. Such a time occurred in 1896 in Cambridge and elsewhere, just after the discovery of X-rays by Röntgen in Munich, and another in 1912 in the laboratory of Sir Ernest Rutherford in Manchester, when the present theory of the atom was first formed. In 1896 a new property of matter, radio-activity, was announced by Becquerel in Paris. This, and the study of X-rays, started ideas which have changed our conceptions of matter. Even the most imaginative at that time would have failed to foresee the extension of our knowledge that developed from these two fundamental discoveries. 1896 seems now a very long time ago. It was not until November of that year, it may be remembered, that motor cars might proceed in public without the use of a red flag; it was in that year also that Marconi produced a sensation by transmitting signals successfully over a few hundred yards by electric waves. Although the idea that matter might possibly be composed of minute indivisible particles called atoms was known to the Greeks, it was not till 1801 that the conception of the atom by Dalton played any real part in scientific discovery; and it was not until 1908 that the existence of a single atom was experimentally demonstrated. Dalton based his atomic theory on the proportions by weight of different elements in various chemical substances. He showed that these proportions are exactly those to be expected if each chemical element consisted of a large number of particles, all of which were exactly alike, although each element had its own particular kind of particle. He determined the relative weights of the atoms of a number of elements and supposed that compound bodies were formed by the union of one or more particles of one element with one or more particles of other elements. In the middle of the 19th century the kinetic theory of gases was developed by Lord Kelvin and others. On this theory it was not difficult to explain the chief properties of gases by imagining that the atoms of the gas acted as very tiny, solid, elastic balls. It was even possible to give a rough estimate of the absolute sizes and weights of different atoms. These revealed how very small such sizes and weights were and how apparently hopeless it would be ever to determine them accurately by any known instrument. Because of this many doubted if the atomic theory could ever be verified, and one body of men refused to believe in the actual existence of atoms at all. Their successors until recently lingered among us, an able, energetic, and controversial body, but without the real justification for their doubts which their grandfathers possessed. The first stage in the attack on the structure of the atom was the discovery of the existence of periodic variations in the physical and chemical properties of the elements, which was pointed out most clearly by the Russian chemist Mendeléef in the late 'sixties. This work made the existence of atoms probable because these variations were most simply explained by regarding the atoms as, in some way, connected units. Mendeléef arranged the elements in the order of what is called their atomic weights. Hydrogen, the lightest element, came first, then the next lightest, and so on till the very heaviest, uranium, was reached. He then noticed that an element resembled, in its properties, not those that were nearest to it in the series of atomic weights, but certain other elements which occurred at definite intervals from it. For example, the group of elements, of which potassium and sodium are best known, called 'alkalis,' comprises the 3rd, 11th, 19th, 37th, and 55th in this series; the halogens,' such as chlorine and iodine, the 1st, 9th, 17th, 35th, and 53rd; while the group distinguished by the peculiarity that its members have no chemical properties at all comprises the 2nd, 10th, 18th, 36th, and 54th. The intervals between successive members of each of these groups are 8, 8, 18, and 18, and in groups of this kind all the chemical elements may be classified. These are, of course, examples of the Periodic System of classification well known to chemists, which is more thoroughly accepted and made use of now than at any earlier period. The periodic system, by emphasising the similarities between atoms of different substances, suggested an explanation of these by similarities in the arrangement of their supposed constituent particles. And as it was simplest to imagine that these particles were all alike, it looked as though atoms were all built up from one fundamental substance. But if so, what is this sub |