many small hospitals, and by the steady increase in the employment of specially trained nurses in private practice, even in rural districts. The result of a case of typhoid or of pneumonia often depends as much upon the nurse as upon the doctor; and affection cannot take the place of skill in either. For the great mass of the people, cases of severe illness or injury, or those requiring major surgical operations, can be treated more successfully in well-appointed hospitals than in private houses, and as this is becoming generally understood the old feeling against entering a hospital for treatment is rapidly disappearing. Improvement in hospital construction and management has kept pace with progress in medical knowledge; and in future such institutions seem destined to play an increasingly important part in municipal and village life.

All progress in civilisation is attended with injury to some individuals. Trained nurses have deprived some unskilled labour of employment; hospitals have injured the business of some physicians; pure-water supplies, good sewers, food inspection, vaccination,-in short, all effective measures in public hygiene,-interfere with the trade side of medical practice; but upon the whole the public at large benefits by all these things. In one sense they seem opposed to the general law of evolution, in that they prolong the life of the unfit; but in a broader sense they work in accordance with this law by increasing the power of the strong to protect and care for the weak.

All told, the most important feature in the progress of medicine during the century has been the discovery of new methods of scientific investigation, more especially in the fields of bacteriology and pathology. These methods have been as yet only partially applied, and great results are to be hoped from their extension in the near future. They will not lead to the discovery of an elixir of life, and the increasing feebleness of old age will

continue to be the certain result of living a long time, for the tissues and organs of each man have a definitely limited term of duration peculiar to himself; but many of the disorders which make life a burden in advancing years can now be palliated, or so dealt with as to secure comparative comfort to the patient, so that "if by reason of strength" life can be prolonged beyond threescore years and ten it no longer necessarily involves labour and sorrow.

SCOPE AND TENDENCIES OF PHYSICS

THE

BY OLIVER LODGE

HE chief scientific event at the beginning of the past century was the discovery of the electric current by Volta. This discovery opened a new chapter in physical science—a chapter which has now become a book of many volumes. But it is within the latter half of.the century, and since the discoveries of Faraday, that its extreme importance has been recognised; and it is within the last twenty-five years that its direct application on a large scale to ordinary human existence has begun. Already the applications of the electric current to human life bid fair to rival those of steam, if they do not already surpass them. Every telegraph and telephone message, every dynamo current, depends on the discoveries of Volta and Faraday. It is impossible to overestimate the gain to humanity of the work of some quiet seeker after truth who happens to be favoured with success in that quest. From his time onward the benefit gradually increases, until it becomes so incorporated with their lives that people cease to think of it, accepting it in the unheeding way they accept the sun, and the air, and the soil. It is perhaps for this reason that they make so little effort to encourage a purely scientific explorer; they do not realise that facts which seem at first small and insignificant may bring forth fruit a thousandfold, and that whereas those who exploit and apply them usually need no encouragement beyond that which they freely receive, the original discoverer may be hampered and hindered in

his work by the penury which accompanies non-recognition. It was the uniquely endowed laboratory of the Royal Institution, London, which enabled Faraday to realise his genius. Men able to experiment are not lacking: laboratories, research laboratories, and leisure to employ them, are the urgent need of all countries at the present time.

But although the foundations of modern electricity were being laid at its beginning, scientific progress during the first quarter of the century lay chiefly in the domain of optics. The mathematical possibilities of the wave theory of light kindled enthusiasm in the great physicists of that day, and discoveries of the utmost brilliance in optics were rapidly made. The names of Young and Fresnel and MacCullagh stand out luminously in this period, as does that of Huyghens in the epoch immediately preceding. The investigation of interference and diffraction, and the discovery of polarised light, are not so widely appreciated as work of less merit in some other departments is; nevertheless, not only were the highest mathematical and experimental powers required for their elucidation, but there is a completeness and finish about these researches hardly to be found anywhere else, except in the dynamical theory of astronomy, the theory which we owe to Newton. It was probably this completeness and finish which delighted and satisfied the great French physicists of the period; and to them in great part our knowledge of the highest refinements of optics is due. The wave theory of light was not, however, strictly speaking, dynamical; that is to say, it was not directly based upon Newton's laws of motion and the straightforward mechanics of matter. Indeed, the actual dynamical basis of the wave theory was by no means clear, nor is it thoroughly clear even at the present day. Nevertheless, the wave theory, so far as it went, admirably fitted the facts, and incorporated the whole of optics in a systematic

and comprehensive way, so much so that it may almost be said that nothing of the first magnitude has been done in that subject since, always excepting the discovery and the applications of spectrum analysis—the analysis of light into its ingredients, as emitted each by a simply vibrating source.

During the next quarter of the century scientific progress lay chiefly in the department of heat and energy, and in the accumulation by Faraday of a mass of experimental materials ready for the organisation and systematisation of a later period. The works of Carnot and of Joule belong essentially to this epoch. The names of these two men are not so well known outside scientific circles as their genius and the importance of their discoveries warrant. Carnot died young, having laid the foundation for a comprehensive theory of all engines whose motive power is heat. Joule lived to old age, but worked quietly and secludedly in a suburb of Manchester, declining many of the scientific honours which would have been heaped upon him and which might have brought his name into more public notice, happy only in his work and in its full and enthusiastic recognition by the leading spirits of his time. Hence to the outer world his name is comparatively unfamiliar. The result of all his work and that of his contemporaries is the unification of physics under the great generalisation called the conservation of energy; and the far-reaching theory of Helmholtz, developed from that of Mayer, as to the gravitative source of solar radiation energy, was thereby rendered possible.

The third quarter of the century is dominated by the names of Kelvin and Maxwell and Helmholtz. In it our theoretical and practical knowledge of electricity and its properties were widely extended, and an intimate connection was perceived between electricity and light. A great mathematical theory of electricity was elaborated