rather than defying current fashions and authorities, have grafted their art on the life of an older tradition. Thus Alfred Stevens, refusing the academic training of the time, put himself to school with the early masters of the Italian Renaissance and silently formed the grand style which marks him as our greatest sculptor. Thus, too, Mr Watts fed his genius at similar sources and attained, unhelped by any contemporary example or support, a largeness and richness which recall the greatest periods of art. To Mr Watts, as we have observed, Mr MacColl is singularly cold, and, however much we may concede to personal opinion, seems singularly unjust. Mr Watts has created in his painting an ideal type which is noble and satisfying, and yet warmly human; the Childhood of Jupiter,' the 'Ariadne,' the 'Roman Lady,' are witnesses sufficient. Etty had failed in attempting this, as Reynolds had failed before him. Mr MacColl is eloquent in praise of Stevens for just this reason, that he could conceive and carry out heroic figures; and Stevens's ideal type is less racial and more abstract than Mr Watts's. Why is the same meed of praise for so rare a success not accorded to the living painter? Again, our critic finds it a capital weakness that Mr Watts has been attracted by more than one ideal and has tried various styles. Yet with what sympathy Mr MacColl records the shifting attitudes of Delacroix, and his attempt to combine Michelangelo with Velasquez! Conflicting ideals have, as he points out in many places, marked the whole century; and few are the artists who have not known the conflict.

We have been led to combat a good many of Mr MacColl's opinions, and to criticise what we cannot but consider mischievous errors in proportion. Let us end with an example that we can cordially praise-his treatment of the art of Whistler. As we might expect from Mr MacColl's natural likes and interests, this art is one which rouses his spontaneous enthusiasm. We might, indeed, expect that his enthusiasm would lead him to suppress the weak side of the artist and ignore his limitations. But his treatment of Whistler's paradoxes, whose wit has led so very many to think that they are wise, could not be juster or more sane. Whistler claimed that art should appeal to the artistic sense of eye or ear;

all else was 'clap-trap.' But, as Mr MacColl points out, we must, on such premises, pronounce Rembrandt a dealer in clap-trap because,

'having taken in hand a scene in which devotion, pity, and other emotions are implicated, he has been so artless as to use all his resources of drawing and tone to reinforce them. In the print of the "Crucifixion" the black and white would give some pleasure to the sense as a pattern in black and white only; but this pattern becomes ingeniously beautiful only when the black and white are seen to be significant, to be the lights and shadows of things and persons; and it becomes sublimely beautiful, sublime to the spirit as well as beautiful to the sense, when the shadows are seen to be the shadows of tragedy.'

Again, Whistler protested that the Portrait of his Mother' was 'an arrangement in grey and black,' nothing more. Human interest was irrelevant, nay, alien to art; it was a matter about which, in this case, the public had no right to trouble itself. What can or ought the public (he asked) to care about the identity of the portrait? Mr MacColl replies:

'The public need not be enlightened on that point; but it will see, because it is presented to its eyes, a great deal more than grey and black, which might have been obtained, uncontaminated by any but the faintest human feeling, from the coal-scuttle.'

This is well and wittily put. But the whole chapter is an admirable statement of the truth, so often confused by discussion, about the relation of subject and treatment, idea and pattern. Would that the whole of Mr MacColl's volume had been informed by the same reasonableness; that the same soundness of judgment, the same sense of measure and fitness had been maintained and developed in a consistent attitude of mind. The book would then have been as valuable for its criticism as it is interesting and important for its history.

LAURENCE BINYON.

100

1. Conduction of Electricity through Gases. By J. J. Thomson, F.R.S. Cambridge: University Press, 1903. 2. Les nouvelles substances radioactives, et les rayons qu'elles émettent. Par P. Curie et Mme Curie. Rapports présentés au Congrès International de Physique. Tome III, p. 79. Paris: Gauthier-Villars, 1900.

3. Recherches sur les substances radioactives. Thèse présentée à la Faculté des Sciences de Paris. Par Mme Curie. Paris: Gauthier-Villars, 1904.

4. Radioactivity and Radioactive Change. By E. Rutherford, F.R.S., and F. Soddy. Philosophical Magazine, Series 6, Vol. v. London: Taylor and Francis, 1903. SCIENTIFIC investigation, which usually proceeds unmarked by most of those not directly engaged in it, is from time to time forced on the attention of the public by some discovery of immediate and striking advantage to mankind, or by the attainment of some theoretical result, which, from its novelty and interest, fires the imagination of every thinking man. To those who follow closely the course of research, these brilliant advances in knowledge rarely come suddenly. The slow and patient work of many observers through long years often leads up to and suggests the particular step from which follows, almost of necessity, the practical application or the far-reaching theory. The mathematical genius of Clerk Maxwell, the experimental skill of Hertz, laid the foundations on which, some years afterwards, was reared the superstructure of wireless telegraphy. The observations of Crookes, Lenard, J. J. Thomson, and many others, on electric discharges through rarefied gases, had given to the physicist an extended insight into the nature of these phenomena, before Röntgen's almost accidental discovery, that photographically active rays thus obtained could traverse certain substances opaque to light, revealed the bones in his hand to the man in the street.

General attention has lately been directed to the subject of radio-activity. M. Curie demonstrated that the stream of energy constantly proceeding from the newly discovered element radium could be detected by a measurable rise of temperature in a small quantity of the substance protected from loss of heat; and the publication

of this result was followed by a correspondence in the 'Times,' in which some surprising efforts were made to explain the source of the energy, and to elucidate the 'mystery of radium.' In this case also the phenomena have been under investigation longer than is generally known; and their detection naturally arose from a knowledge of the properties of Röntgen rays. These rays produce fluorescent effects on suitable screens; and it was natural to examine phosphorescent and fluorescent substances, to determine if they were the source of similar radiation. For some time no definite results were obtained; but, in the year 1896, M. Henri Becquerel discovered that compounds of the metal uranium, whether phosphorescent or not, affected a photographic plate through an opaque covering of black paper, and rendered the air in their neighbourhood a conductor of electricity. Such were the first observations on the property of radioactivity; but the rapid development of the subject which has followed could only have taken place with the aid of our previous knowledge of the electrical properties of gases. Although the superficial similarity between Becquerel rays and Röntgen rays has proved for the most part misleading, the relations between the two branches of the subject are so intimate that it is impossible to study satisfactorily the phenomena of radioactivity without a knowledge of the results previously and simultaneously reached by the investigation of electric discharge through gases.

Hitherto, in order to obtain such knowledge, it was necessary to examine the chief papers on the subject, scattered through a dozen English and foreign journals; but Professor J. J. Thomson has now collected the extensive material in the valuable work lately published. Not only has Professor Thomson contributed perhaps more than any other man to the development of this branch of knowledge, but a school of research has grown up under his inspiration at the Cavendish Laboratory which draws students from all civilised countries and forms an organised band of explorers into this region of the unknown. Many of his former students are now carrying on the work of research in other places; and one of them, Professor Rutherford of Montreal, in a series of brilliant investigations undertaken during the

last few years, has added largely to our knowledge of the phenomena and causes of radio-activity. To his papers, published chiefly in recent numbers of the 'Philosophical Magazine,' we must turn if we wish to comprehend the later developments of this most interesting and important subject. We are glad to learn that Professor Rutherford intends to embody the results of his experiments in a book; we may expect that, in this work, the subject will receive fuller treatment than is possible in a volume like that written by Professor Thomson, which, covering a much wider field, only contains one chapter devoted to radio-active processes.

Several popular accounts of recent developments in physical theory have appeared. Sir Oliver Lodge discussed ether and matter generally in his Romanes Lecture at Oxford in 1903; and readers of the 'Times' have been able to follow the more important discoveries in radioactivity as they were made. The whole realm of natural knowledge is the theme of a book on 'New Conceptions in Science' written by Mr Carl Snyder (Harper, 1903). This is a bright and entertaining volume, in which even the professed physicist may find statements that are new to him. It appears, to begin with Mr Snyder's 'new conceptions' of the ancients, that Archimedes' discovery,' which enabled him to test the purity of the gold in King Hiero's crown, 'was that a body in water displaces a quantity of water of equal weight, and not according to its bulk, as one might believe at first thought.' It might have been well, in this case, to have acted on the assumption that first thoughts may after all be best. perhaps by 'in water' is meant 'floating on the surface.' If so, the sentence reflects little credit on the author's power of expression, or on his knowledge of the true import of the principle of Archimedes. Passing to modern times, we are told that if our eyes were sensitive to these electrical waves' used in wireless telegraphy, 'then we might watch the progress of a play in Buenos Ayres, or have witnessed the struggles in Pekin.' We have yet to learn that even South American acting is the source of electro-magnetic radiation; while the possibility of distinct vision certainly depends on the extreme minuteness of the waves of light compared with the dimensions of the visible object, Mr Snyder is an

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