The progress of science—like human progress in all directions—is a somewhat irregular process. In this process we can generally distinguish several stages, which, however, merge constantly into one another. The first stage is that of the collection of scientific data; the next, some sort of logical arrangement of the data; and finally, generalizations made in the effort to interpret the phenomena. This chronological arrangement, however, is subject to constant variations. The human mind is active in the construction of theories formed far in advance of positive knowledge; and while such theories are often erroneous, they nevertheless serve to stimulate investigation and to lead ultimately to truth. Scientific progress is thus made up of a continuous series of collections of fact, while efforts at interpretation occur, not in their chronologic order, but rather in the order in which the temperaments of men and the tendencies of the age may suggest.

For this reason it is seldom possible to compare sharply the state of science at two distinct epochs. There are, to be sure, discoveries which belong to a given year, but they are ordinarily the culmination of long periods of collection and comparison of facts, which represent rather processes than distinct efforts, and the men who contribute most to the collection and correlation of facts are often unknown to the public.

Furthermore, it is to be remembered when one considers physical science, that the facts and the phenomena of science are the same to-day as fifty years ago. Chemical reactions, the nature and the growth of microbe organisms, the transformations of energy, are the same in nature to-day as they were a half-century ago. For this reason, the state of science at two distinct epochs cannot be contrasted in the same way as one might compare two epochs in a creative art, such as literature, in which a whole new school of authors may have grown up in consequence of a new social factor or a new literary cult.

Comparisons of scientific progress at two distinct epochs resemble rather two views from a mountain, one view-point a little higher than the other, each looking out upon the same topography, but showing hills and valleys and streams in greater detail or with greater clearness from one point than from the other by reason of the difference in altitude. In some such way one may compare the outlook in science to-day with that of a half-century ago; the facts and the phenomena are the same, the point of view has changed enormously.

To bring such a view within the compass of a brief discussion, one needs also to keep in mind two other facts. First, that in making such a comparison, one is viewing the scientific horizon, not from the standpoint of the specialist in any department of science, but rather from the standpoint of the educated American. Such a man is not interested in the minute subdivisions of science, nor in the names of the specialists who have served it; but rather in the outcome, in the direction both of utilitarian ends and of intellectual and moral results, which the progress of science promises to the race. Second, in making such a comparison from the standpoint of the general reader, it is most important to keep in view the unity of human knowledge. Science is essentially one, and while, for the sake of convenience, it must be classified into numerous subdivisions, these parts have a relation to the whole. Thus, physical science not only concerns itself with the objective world, but it goes far beyond this and works at the relation between human circumstances and the necessary laws which govern physical objects. In the same way, the historical sciences transcend the social phenomena with which they are immediately concerned and attempt an interpretation of these in the light of physical law. Thus all divisions of science are inextricably yoked together in the common effort to explain the history of man, and the adjustment of the human race to its environment.

When one considers a science in this larger aspect he realizes that the middle of the nineteenth century and the beginning of the twentieth are two extremely interesting epochs to compare. After centuries of accumulation of facts, the men of the first half of the nineteenth century had begun those great generalizations which the mid-century saw securely in the grasp of the human mind, and the fifty years which have since elapsed have borne a rich fruitage of those generalizations.

The fundamental contrasts which stand out most prominently in such a comparison may be grouped under four heads: —

1. The last fifty years have seen a great betterment of the theoretical basis of physical science.

2. This development has been marked by a notable stimulation of scientific research, a differentiation of scientific effort, and the creation thereby of a great number of special sciences or departments of science.

3. The possession of a secure theoretical basis and the intellectual quickening which has followed it have resulted in the application of science to the arts and to the industries in such measure as the world has never before known. These applications have to do with the comfort, health, pleasures, and happiness of the human race, and affect vitally all the conditions of modern life.

4. Last, but perhaps in many respects the most significant of all, is the effect which has been produced upon the religious faith and the philosophy of life of the civilized world by the widespread introduction of what may be called the modern scientific spirit.

I shall endeavor to point out the more significant movements which group themselves under these four heads, begging the reader always to bear in mind the fundamental facts to which I have alluded, that is to say, the desire to present a view, not of the scientific specialist, but of the educated intelligent American; and secondly, to keep in mind at the same time, notwithstanding the differentiations of science, the essential unity of human knowledge.

The Betterment of the Theoretical Basis of Physical Science.

The fundamental sciences which have opened to us such knowledge of the laws of the universe as we now possess are mathematics, chemistry, and physics. The first of these deals with numerical relations, and it has been the tool with which the human mind has had most experience. It had advanced to a high stage of perfection long before any other branch of science had attained even respectable standing. Men learned to reason in abstract relations with great skill and proficiency long in advance of the time when they reasoned from physical phenomena to their cause. The end of the eighteenth century and the beginning of the nineteenth saw a galaxy of astronomers and mathematicians of whom Laplace and Gauss were the most fruitful, who carried mathematical treatment of the problems of astronomy and geodesy to a point which left little to be desired. The last century has seen little improvement in these processes, but mathematics has remained the most facile tool in the hands of the physical investigator, in the interpretation of physical phenomena, and in the expression of the transformations of energy. But for the significant progress which has been made in the last fifty years we are indebted to the other two fundamental sciences, chemistry and physics. The first deals with the composition and transformation of matter; the second with energy and the transformation of energy.

The connection between physics and chemistry is so intimate that it is impossible to draw a line of separation. In general, we are concerned in chemistry with the elements which, by their combination, form various substances, and with the composition of these substances; while in physics we are concerned with matter as a mass, as a substance representing a fixed composition, though subject to changes of form and of place. Changes by which the identity of the body is affected, such as, for example, when hydrogen and oxygen combine to form water, are chemical changes and do not belong to physics; while changes which matter undergoes without altering its composition or destroying the identity of the body are physical and are part of the study of physics. Inasmuch, however, as chemical changes are accompanied by changes of energy, there is a broad region which belongs to the investigations both of the physicist and of the chemist, and which completely connects those two fundamental sciences.

In the early part of the nineteenth century, John Dalton announced his famous atomic theory, which has served to unify the known or suspected laws of chemical combination. Dalton discovered that to every element a definite number could be assigned, and that these numbers, or their multiples, govern the formation of all compounds. Oxygen, for instance, unites with other elements in the proportion of eight parts of weight, or some multiple thereof, and never in other ratios. With the help of these atomic weights—or combining parts, as they are sometimes called—the composition of any substance could be represented by a simple formula. This theory had become well established by the middle of the nineteenth century as the thread upon which all chemical results hung, and the second half of the century began under the stimulation which this discovery brought about. Before this period, inorganic chemistry—that is, the chemistry of the metals, of earths, of common oxides, bases, and salts—had received the greatest attention, and during the first half of the nineteenth century inorganic chemistry embraced almost all the work of chemists. The second half of the nineteenth century has been the day of organic chemistry. It was at first supposed that the two fields of research were absolutely distinct, but this belief was overthrown by Woehler, who showed that urea, an organic body, was easily prepared from inorganic materials, and since that day a vast number of organic syntheses have been effected. Out of this study has grown the basis of the chemical theory of to-day, that is to say, the conception of chemical structure, which has placed the chemistry of the twentieth century upon a theoretical foundation vastly more secure and vastly more significant than that of half a century ago.

Briefly stated, this theory of chemical structure is as follows: Every atom, so far as its union with other atoms is concerned, is seen to have a certain atom-fixing power, which is known as its valence. For example, take hydrogen as the standard of reference, and consider some of its simplest compounds. In hydro-chloric acid, one atom of hydrogen is added to one of chlorine. These elementary atoms combine only in the ratio of one to one. They are called “univalent,” that is, their power of fixing or uniting with other atoms is unity. In water, on the other hand, a single oxygen atom holds two of hydrogen in combination, and so oxygen is called a bivalent element. Nitrogen, phosphorous, and other elements go still farther and are trivalent, while carbon is a quadrivalent substance, forming, therefore, compounds of the most complex type. The theory as thus stated is no mere speculation. It is the statement of observed fact, and this shows that the atoms unite, not at haphazard, but according to certain rules.

A notable advance took place in the years 1860 to 1870 in the discovery of a general law connecting all the chemical elements. That those elements are related was early recognized, but it was not until the epoch-making work of Mendeléeff that the periodic variation in their properties was recognized, and the connection between the valency of the atom and its properties and compounds was interpreted.

Within twenty years chemistry has been enormously developed upon its electrical side, both theoretically and practically. From a purely chemical point of view, probably the most important electrical phenomena are those of electrolysis. When a current of electricity passes through a compound solution, the latter undergoes decomposition, and the dissolved substance is separated into two parts which move with unequal velocities in opposite directions. The conducting liquid is called an electrolyte, and the separated parts, or particles, of the compound in solution are termed its ions. One ion is positively, the other negatively electrified, and hence they tend to accumulate around the opposite poles. Under suitable conditions, the separation can be made permanent, and this fact is of the greatest significance in the different processes of electrometallurgy.

The modern science of physics has its basis in the doctrine of the conservation of energy. This doctrine as stated in the words of Maxwell is: “The total energy of any material system is a quantity which can neither be increased nor diminished by any action between the parts of the system, though it may be transformed into any of the forms of which energy is susceptible.” A little more than a half-century ago, our knowledge of physics consisted in the main of a large mass of facts loosely tied together by theories not always consistent. Between 1845 and 1850 the labors of Mayer, Joule, Helmholtz, and Sir William Thomson had placed the theory of the conservation of energy upon firm ground, and for the last half-century it has been the basic law for testing the accuracy of physical experiments and for extending physical theory. To the presence of such a highly defined and consistent theory is due the great development which our generation has witnessed.

The most remarkable development of the half-century in the domain of physics has gone on in that field included under the name radio-activity, a development which bids fair to affect the whole theory of physical processes. By radiation is meant the propagation of energy in straight lines. This is effected by vibrations in the ether which fills all space, both molecular and inter-stellar. This theory is based upon the conception that the vibrations are due to oscillations of the ultimate particles of matter.

Experiments in vacuum tubes by various investigators led to a long series of most interesting results, culminating in the discovery by Roentgen in 1895 of the so-called X-rays. These rays have properties quite different from those of ordinary light. They are not deflected by a magnet and will penetrate glass, tin, aluminum, and in general metals of low atomic weight. In 1896, Bequerel discovered that uranium possessed the property of spontaneously emitting rays capable of passing through bodies opaque to ordinary light.

Shortly after the discovery of this property in uranium Madame and Professor Curie succeeded in separating from pitchblende two new substances of very high radio-activity, called radium and polonium, the latter named after her native land, Poland.

The radiations from these various substances are invisible to the eye, but act upon a photographic plate and discharge an electrified body. A very active substance like radium will cause phosphorescent substances to become luminous.

If a magnetic field is applied to a pencil of radium rays the rays are separated out into three kinds, much as light rays are sifted out by passing through a prism. One set of rays is bent to the left, another to the right, and the third set keeps on in the original direction.

The emission of the particles which deviate to the left and right appears to proceed from explosions in some of the atoms of these substances. It is estimated that two hundred thousand millions are expelled from one gram of radium bromide every second, yet the number of atoms in a gram is so enormous that this rate of emission may continue some years without an appreciable wasting of the mass of the substance.

The discovery of these substances with their remarkable properties has not only led to interesting applications of the most novel kind, but has stimulated the imagination of investigators, and given rise to various new explanations of cosmic phenomena. For example, it has been suggested that the internal heat of the earth may be kept up by the heat emitted from radium and other radioactive matter. All such theories are yet in the speculative stage. It may be said in general that, while the phenomena presented by the radio-active substances have caused physicists to revise physical theory in respect to molecular energy, nothing has been discovered which is inconsistent with the fundamental law of the conservation of energy.

Progress no real has been made in those sciences which deal with the study of the human body and the human mind. Physiology, during the last half of the nineteenth century, has gained nearly all our present knowledge of the chemistry of digestion and secretion and of the mechanics of circulation, while psychology has advanced from a branch of philosophy to the position of a distinctive science.

From whatever point of view one regards human progress, he will be led to realize that one of the greatest achievements of the race is the work of the army of scholars and investigators to whom is due the betterment in these fifty years of the theoretical basis of these two fundamental physical sciences, a basis which is not only intellectually sound, but intellectually fruitful. The roll of these names—chemists, physicists, biologists, inventors, investigators in all fields of human knowledge—is made up from all lands. It is a world’s roll of honor in which not only individuals but nations have earned immortality. Of all the men whose names are here written, there are two whose work is so fundamental and far-reaching that the world is glad to accord to them a preëminence. These are the Frenchman, Louis Pasteur, and the Englishman, Charles Darwin.

The Differentiation of Science and the Development of Special Sciences.

Under the stimulus of the great fundamental theories which have tended to unify chemistry and physics, and also to direct attention to a vast field common to both and previously unexplored, a large number of special sciences, or divisions of science, have been developed. Once the law of chemical structure was ascertained and the possibilities were made evident which this law involved, and once the law of the conservation of energy was clear and the multiform transformations which might be made under such a law formulated, there was opened in every nook and corner of the physical universe the opportunity for new combinations and for new transformations. The result of this has been that in the last five decades physicists and chemists, having these threads in their hands as guides, have gone off into all sorts of by-paths. There has grown up through these excursions a great number of minor divisions of science, dependent on processes partly physical and partly chemical, but all related to one another and to the fundamental sciences of chemistry and physics.

By means of that wonderful instrument, the spectroscope, has arisen the combination of the old science of astronomy with physics, known as astro-physics. There have been interesting gains in the older astronomy during this period, such as the discoveries of the new satellites of Mars, of Jupiter, and of Saturn, all by American astronomers; the discovery of some hundreds of asteroids with the unexpected form of some of their orbits; and the variation of the terrestrial latitude. All these discoveries are in the direction of the applications of gravitational astronomy upon the foundations laid by Newton, Laplace, and Gauss. The significant gains have come, however, in the new astronomy, which is really celestial physics, and are the outcome of the modern spectroscope and photographic plate. The motion of stars and nebulæ in the line of sight, the discovery of invisible companions by the doubling of the lines of the spectrum, and above all, the determinations of the physical constitution of the distant suns and nebulæ have thrown a great light not only upon cosmic evolution, but upon the probable history of our own planet. Perhaps no one result of the whole study is so significant at this: IN the far-distant suns which shine upon us, as well as in our own sun, we find only those same elements which exist in our own soil and in our own atmosphere. Just as the law of the combination of chemical elements and of the conservation of energy points to a uniform physical law on our planet, so also the unity of material composition throughout the universe of stars seems to point with equal significance to a physical unity of the whole universe.

Early in the seventeenth century, certain “animalculæ,” as they were called, became recognized as the simplest form of life; but the modern science of bacteriology dates from the epoch-making investigations of Pasteur and Koch, conducted within the last thirty-five years. One of the most important steps was the introduction by Koch of trustworthy methods for separating individual bacterial species. Since many distinct species are indistinguishable from one another by size and shape, it was obviously impossible by the older methods of study to separate one from the other. Koch suggested the use of solid materials as culture media, thereby representing the conditions so often seen when such organic matter as bread becomes mouldy. He demonstrated that the addition of gelatin to the infusions employed for the successful cultivation of bacteria converted them into practically solid culture media without robbing them of any of their useful properties; and by the employment of such media it was possible to separate as pure cultures the individual species that one desired to analyze. The introduction of this method for the isolation and study of bacterial species in pure cultures constitutes perhaps the most important stimulus to the development of modern bacteriology.

The studies made by Pasteur upon fermentation and the souring of wine, and upon the maladies of silkworms, together with Koch’s studies upon the infections of wounds, and the appropriate methods of analyzing them, were rich in suggestion to the workers in this new field. Two of the most important results have been in the application of these studies to the problems of the sanitary engineer and to the work of preventive medicine.

The drinking water of our cities is purified to-day by the process of natural sand filtration, by the septic tank process, etc. In these methods the living bacteria are the instruments by which the results are obtained. The sand grains in the filters serve only as objects to which the bacteria can attach themselves and multiply. By the normal life processes of the bacteria the polluting organic matter in the water is used up and inert material given off as a result.

But even more important than this work of sanitation is the contribution of bacteriology to preventive medicine. Early in the course of his work, Pasteur discovered that certain virulent pathogenic bacteria, when kept under certain conditions, gradually lost their disease-producing power, without their other life properties being disturbed. When injected into animals in this attenuated state, there resulted a mild, temporary, and modified form of infection, usually followed by recovery. With recovery the animal so treated was immune from the activities of the fully virulent bacteria of the same species. The development of this fruitful idea has not only resulted in the saving of millions of money, but it has resulted as well in the prevention of human disease, the greatest triumph of modern science.

A study of the laws of physics and chemistry in relation to living plants and animals led in a similar way to the discovery that the processes of the entire race history are reflected in the processes of the growth of the embryo, a result which created the new science of embryology.

Similarly, in the studies of energy differentiations have gone on. Fifty years ago, our colleges had a single professor of what was called at that day natural philosophy. To-day, a modern college will divide this field among a corps of teachers and investigators, one devoting his attention to mechanics, another to heat, another to electricity, another to magnetism, and another to sound and light. In turn, electricity will be subdivided, the investigator concerning himself with a constantly narrowing field of phenomena, with the expectation of working out completely the problem whose solution is sought. All these departments of physical science, with their numerous subdivisions, are the offspring of the fundamental sciences chemistry and physics. No contrast is more striking in comparing the science of to-day with that of fifty years ago than this differentiation, unless it be the even more significant fact that, notwithstanding this differentiation and division of labor, the essential unity of science is more apparent than ever before. Astronomy, geology, and biology were, fifty years ago, separate, and to a large extent unrelated, sciences. To-day they are seen to flourish in a common soil.

The Application of Science to the Arts and to the Industries.

In no other way has the march of science in the last half-century been so evident to the eyes of the average intelligent man as in its practical applications to the arts and industries. Modern life to-day is on a different plane from that of fifty years ago by reason of applied science alone. Whether this has added to the joy of living, and to the general happiness of mankind, is another question; but that it has raised the standard of health, that it has added enormously to the comfort and to the conveniences of man, no one can dispute. The house of fifty years ago lacked the facilities of pure water; it was illuminated, at the best, by imperfect gas jets; it was warmed by the old-fashioned stove; and if situated in an isolated place, communication was possible only by messenger at the expense of time and labor. The modern sanitary water service, electric lighting, modern means of construction, and the telephone, make the dwelling-house of to-day a wholly different place from the dwelling-house of fifty years ago.

Steam transportation had already begun its marvelous work before the epoch at which we start, but its great application has been made in the last half-century. Just as the fruitful theories of physics and chemistry have advanced physical science in all its applications, so also the elementary development and applications of steam have blossomed in the last half-century into a transportation system which makes the world of to-day a wholly different world from that of fifty years ago.

Perhaps the fundamental application of science which has done the most to change the face of the civilized world is the invention by Sir Henry Bessemer of a cheap means of manufacturing steel from pig iron. On August 13, fifty-one years ago, he read before the British Association at Cheltenham a paper dealing with the invention which has made his name famous. His paper was entitled “The Manufacture of Malleable Iron and Steel without Fuel,” and described a new and cheap process of making steel from pig iron by blowing a blast of air through it when in a state of fusion, so as to clear it of all carbon, and then adding the requisite quantity of carbon to produce steel. Not one man in ten thousand knows who Sir Henry Bessemer was or what he did, but every man who touches civilization leads to-day a different life from that which he would have led, by reason of Bessemer’s invention. Cheap steel is the basis of our material advancement.

One of the most interesting applications of chemistry is that involved in the manufacture of aniline colors. Up to the time of the investigation of Sir William Perkin in 1856, commerce had depended on vegetable colors, which had been obtained at great cost and difficulty. That these rainbow hues could ever be procured from so insignificant a substance as coal tar seemed as improbable as anything which one could imagine, and yet from the labors of the chemist there have come in the last thirty years colors surpassing in beauty anything produced by nature. The manufacture of such colors has come to be a great industry, employing thousands of men and enormous capital, and this too out of a waste product which manufacturers were once quite ready to throw away.

One of the most interesting combinations of chemistry and physics is that shown in the modern photograph. Photography as an art had reached a considerable stage of development by the early fifties, but the wet collodion process, as it was called, while possible for the professional, was difficult for the amateur. Plates had to be prepared and finished on the spot, transportation was difficult, and there was a demand for a process which could be used in the field as easily as in the office. The first step came in 1856 in the invention of what was called dry collodion, followed rapidly by similar inventions which did away with the troublesome preparation of the plate in the silver bath. Out of the process has grown the modern photographic dry plate, and the modern camera, an instrument so convenient and easy of transportation, and yet so safe and sure in its results, that on the wildest expeditions the most perfect photographs can be taken.

To-day the word which best represents to the popular mind the triumphant application of science is the word “electricity.” The fruitful idea that electricity, like light, was only a form of energy, lies at the base of the great inventions which have been made. The moment that electricity was produced by transforming other forms of energy, there became possible all sorts of machines which could not be imagined under any other hypothesis. It was in the development of this idea that the inventors have perfected during this half-century the electric motor, the electric light, the telephone, and the thousand separate devices by which mechanical energy in transformed into electric energy, and this again into heat or light. It is the machines for these marvelous transformations which have been invented in the last generation that have made the greatest difference in our modern life. The storage battery, the arc light, the incandescent light, and the telephone have all come in as actual parts of our every-day life within the memory of men of middle age, and, as a crowning exploit of the century, telegraphy without wires brings us messages from ships in mid-ocean. In every department of domestic life, in every line of transportation, in almost all methods of communication between men and cities, the application of electricity has come to play a great rôle. So numerous are these applications, so important are they to our comfort and to our well-being, that we have ceased to wonder at them, and year by year new applications are made which a few decades ago would have called forth astonishment, but which we receive as a part of the day’s work. So great is this field, so promising are the applications which we may hope to see made, that no man can foretell what the inventions of the future may be.

To-day we are interested not less in the applications of electricity than in its supply. So well is the law of transformation of energy now understood and so sure are the results of our inventors, that we may confidently expect that the applications of electricity to the arts and industries will reach almost any point of perfection. A vital question is, can a supply of energy be found which can be efficiently and cheaply transformed into electric energy?

At present our chief source of electricity is coal, and the century just closing has given no particular indication of a possible rival to coal, unless it be water power. Over a large part of the earth’s surface, however, neither coal nor water power is accessible. Furthermore, the supply of coal is limited. It is likely to become in the near future more and more expensive, and one of the great problems which the inventors of our day face is the problem of devising a cheap and effective source of energy for the production of power.

There is one source to which all minds revert when this question is mentioned, a source most promising and yet one which has so far eluded the investigator. The sun on a clear day delivers upon each square yard of the earth’s surface the equivalent of approximately two horse-power of mechanical energy working continuously. If even a fraction of this power could be transformed into mechanical or electrical energy and stored, it would do the world’s work. Here is power delivered at our very doors without cost. How to store the energy so generously furnished, and keep it on tap for future use, is the problem. That the next half-century will see some solution thereof, chemical or otherwise, seems likely.

Perhaps in no way have the applications of science so ministered to human happiness as in the contributions of the last fifty years to preventive medicine, surgery, and sanitation. Within this half-century Pasteur did his great work on spontaneous generation and in the development of the theory of anti-toxins. Following in his steps, Lister applied the principles which Pasteur had enunciated, in the treatment of wounds and sores. The whole outcome has been a splendid step forward, not only in such matters as the treatment of diphtheria, yellow fever, and malaria, but also in the direction of preventive medicine. The scientific world is organizing for a fight to the death with tuberculosis, that worst malady of mankind, and if there is any such advance in general education and in general knowledge during the next fifty years as in the last, it is not too much to hope that this dread scourge of humanity may be vanquished. In no direction in which science touches life in there a greater contrast between the life of fifty years ago and that of to-day than in these matters of preventive medicine, of surgery, and of sanitation; and it is worth recalling that these advances have come, not through the professional physician or surgeon, but through the laboratory investigations of the chemist and of the physicist. Applied chemistry and physics are the sources from which our sanitary and surgical gains have resulted.

A no less striking application of science in this half-century is to be found in those matters which affect transportation, whether on land or sea. Within this brief span of a generation and a half, steam transportation has been so enormously advanced that the transit of the largest oceans has become little more than a pleasure trip. Within this period the first electric car was set rolling over the earth’s surface, and the whole development of modern transportation, including the automobile, belongs to this half-century.

Equally impressive, but not so often referred to, are the applications of science in the transmission of intelligence. Fifty years ago the land telegraph was in its infancy, and its use was restricted to messages of pressing business importance. Within the span of time of which we are speaking, the telegraph has been developed into an indispensable adjunct of every civilized man’s business. Submarine cables extended under the sea connect all the continents of the earth. Not only have these enormous changes come, but the invention of the telephone makes it possible to transmit the human voice across the space of hundreds of miles; and finally, as a first fruit of the twentieth-century inventor’s work, wireless telegraphy sends its messages through the air with the distant ship to the shore. These applications, which enable each civilized man to know the business of all the rest, are to have an effect on our mode of life, on our relations with other nations, and on the general culture of the civilized world, such as we perhaps cannot even to-day imagine. One of the results of this development in America is the modern newspaper, filled with news form the ends of the earth. The ease of transmission makes it possible to report not only the important things, but the scandal and the gossip, each item of which ought to die in its own cradle. The modern sensational paper is one of the unripe fruits of the scientific applications of our age. Social development in the last half-century has lagged behind scientific progress and application. The education of the American people in obedience to law and in framing effective legislation for the distribution of the proceeds of production are far behind the scientific efficiency of the age. A serious question of civilization is, “How may the nation be rightly educated and wisely led, to the end that the tremendous productivity of applied science may ennoble and enrich, rather than vulgarize and corrupt it?”

The Effect of Modern Scientific Research on the Religious Faith and the Philosophy of Life of the Civilized World.

It is not too much to say that the development of science in these last five decades has produced a greater effect upon the beliefs and the philosophy of civilized man than that of all the centuries preceding. Fifty years ago the scientific world stood upon the brink of a great philosophical conception as to the origin of the system of nature which we see about us. The epoch-making work of Laplace and his contemporary mathematicians upon the development of the solar system, the researches of Lyell concerning the history of our own earth, the work of Buffon and Lamarck, the reflections of the earlier thinkers, like Leibnitz, Schelling, and Kant, all served in their respective branches of science to prepare the world for some generalizations as to the origin of life and the variations of living forms. In human history there had been recognized an evolution, one form of institution growing out of another, one race out of another, one language out of another. The evidence was beginning to be cumulative that the present is the child of the past, and that the living creatures which we see about us have been evolved, being descendants of ancestral forms on the whole simpler; that those ancestors were descended from still simpler forms, and so on backward. What was needed in 1857 was some well-grounded, intelligible explanation of the variation of species. This explanation came in 1859 in the publication of Charles Darwin’s epoch-making book, The Origin of Species by Means of Natural Selection. Darwin showed that in natural selection, or what has also been called “the survival of the fittest,” is found a natural process which results in the preservation of favorable variations. This process leads to the modification of each creature in relation to its organic conditions of lie, and in most cases the change may be regarded as an advance in organization. “Darwinism” is not to be confused with “evolution.” Darwin’s name has been given to one particular interpretation of the process of evolution. The actual fact of development is proved from so many converging lines that there can be no doubt of the fact itself, although the future growth of our ideas may largely modify the explanation that Darwin has given of it.

Perhaps no single work has produced so great an impression upon the spirit of any age as has Darwin’s memorable book upon the intellectual life of Europe and America. The book became at first the centre of a fierce intellectual discussion. Scientific men themselves were divided in their estimate of its importance and its soundness. In Boston, before the American Academy of Science and Arts, there went on during the winter of 1859 and 1860 one of the most spirited scientific debates which our country has ever known, between Professor Louis Agassiz in opposition to Darwin’s theory and Professor William A. Rogers in favor of it. Both were eloquent men, both were eminent in science, and perhaps no series of discussions before a scientific body has been more interesting than those which these two great men carried on at this time.

The outcome of the work of Darwin and his successors has been the practical acceptance by civilized men of the general theory of evolution, however they may differ about the process itself. While the work of the scientific men who have built up the doctrine of evolution, which to-day stands more firmly than ever as a reasonable interpretation of organic nature, was a scientific one and had nothing to do with ultimate problems, nevertheless it was inevitable that such a theory should excite the strongest opposition on the part of the theology of that day. The acrimony of that discussion has long since worn away. Men have had in fifty years a breathing time sufficient to see that however opposed such an explanation of nature may be to the then accepted orthodox theory of creation, neither one nor the other was necessarily connected with true religious life. To-day, in one form or another, nearly all educated men accept the general theory of evolution as the process by which the universe has been developed.

The chief effect, however, of the advance of science during these fifty years upon religious belief and the philosophy of life has come, not so much from the acceptance of the theory of evolution, or the conservation of energy, or other scientific deductions, but rather from the development of what is commonly called “the scientific spirit.” To-day a thousand men are working in the investigations of science where ten were working fifty years ago. These men form a far larger proportion of the whole community of intelligent men than they did a half-century ago, and their influence upon the thought of the race is greatly increased. They have been trained in a generation taught to question all processes, to hold fast only to those things that will bear proof, and to seek for the truth as the one thing worth having. It is this attitude of mind which makes the scientific spirit, and it is the widespread dissemination of this spirit which has affected the attitude of the great mass of civilized men toward formal theology and toward a general philosophy of life. The ability to believe, and even the disposition to believe, is one of the oldest acquirements of the human mind. On the other hand, the capacity for estimating evidence in cases of physical causation has been a recent acquisition. The last fifty years has added enormously to the power of the race in this capacity, and in the consequent demand on the part of all men for trustworthy evidence, not only in the case of physical phenomena, but in all other matters. This spirit is to-day the dominant note of the twentieth century. It is a serious spirit and a reverent one, but it demands to know, and it will be satisfied with no answer which does not squarely face the facts. This intellectual gain is the most noteworthy fruitage of the last fifty years of science and of scientific freedom.

A direct outcome of this development of scientific spirit has been the growth of what has come to be called the higher criticism. The higher criticism is a science whose aim is the determination of the literary history of books and writings, including inquiries into the literary form, the unity, the date of publication, the authorship, the method of composition, the integrity and amount of care shown in any subsequent editing, and into other matters, such as many be discovered by the use of the internal evidence presented in the writing itself. It is termed the higher criticism to distinguish it from the related science of lower, or textual, criticism. This science is almost wholly a child of the last half-century, and in particular is this true so far as Biblical study and criticism are concerned. The development of this school of study along scientific lines has, in connection with the wide spread of the scientific spirit itself, had an enormous effect on the attitude of civilized man toward formal theology and toward formal religious organizations.

What the outcome of this intellectual development will be, whether it will result in a change of the organizations themselves or the evolution of new organizations for religious teaching along other lines than those which now exist, no one to-day can say. Of this much, however, we may be fairly sure: that although the work of the evolutionists and the higher critics may have affected formal theology, there is no reason for belief that the innate religious spirit of mankind has been weakened. True religion is a life, not a belief; and the religious life of the twentieth century promises to be as deep and genuine, and perhaps more satisfactory, than that of the century before. To-day the figure of Jesus Christ looms larger to the world than it did fifty years ago, and partly for the reason that his life and work are being studied apart from formal theology and independently of formal religious organization.

The general effect of the whole evolutionary development of the last fifty years upon the philosophy of life of civilized man has been a hopeful one. The old theology pointed man to a race history in which he as represented as having fallen form a high estate to a low one. The philosophy of evolution encourages him to believe that, notwithstanding the limitations which come from a brute ancestry, his course has been upward, and he looks forward to-day hopefully and confidently to a like development in the future.

One who looks over this half-century of development of science cannot but feel something of this hopefulness as he looks forward to the half-century just begun. So little do we know of nature and of nature’s laws, so large is their intent in comparison, that we may confidently expect the discoveries of the next half-century to more than equal those of the half-century just passed. The applications of chemistry and of physics are now being pushed by thousands of men better trained for research than in any generation which preceded. Organized effort in scientific research is begun; transportation, already so highly developed, will become still more convenient. Preventive medicine may well be expected to make enormous strides in the struggle with the great plagues of mankind. The whole scale of human living, so far as comfort and convenience are concerned, we may confidently expect to improve as rapidly as it has in the fifty years gone by. The house of 1950 will be as much superior in comfort and convenience to our homes of to-day as these are to those of a half-century ago.

Finally, we may be sure that during the next fifty years, as during the past, that question which will most interest man is the old one, What is life and how came it to be? This question has not yet been answered by any fruitful hypothesis like those of Darwin or Lamarck, which have been such effective tools in the hands of investigators. In the aid of the solution of this problem all scientific men are working, either consciously or unconsciously. Much of what they do seems trivial and dry in the eyes of those who are occupied with other thoughts. The man who is engaged in accumulating a million dollars may not easily understand how a student will toil patiently in a laboratory, laboriously gathering together minute data, in order that the generalizers of science may go a step farther in the solution of the great problem. To-day the world stands firmly convinced of the universal force of the principle of evolution, and on the other hand looks forward to the realization of independent life and action in the separate cell. Whether in the next half-century science may be able to vanquish the difficulty presented by that atom of living potential protoplasm, the cell, we cannot say, but we may feel sure that great steps toward its solution will be made, and that these steps will be taken in the service of the truth for the truth’s sake, which is the watchword of the science of to-day.

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