two kinds of lead from each other by fractional crystallization. This was predicted by Soddy, and tested by him and by others. Various vain attempts have been made to separate the different kinds of lead from one another, but apparently when once they are mixed, no chemical method can separate them, since the properties of the different kinds are so nearly alike. The latest attempt at the Gibbs Memorial Laboratory involved one thousand fractional crystallizations of the Australian lead nitrate, which is believed to contain both ordinary and uranium-radium-lead. The extreme fraction of the crystals (representing the least soluble portion, if any difference in solubility might exist) gave within the limit of error the same atomic weight as the extreme fraction of the mother liquor (representing the most soluble portion), thus confirming the work of others in this direction. When wires constructed of two different metals are joined, and the junction heated. an electrical potential or electromotive force is produced at the junction. This property seemed, then, to be a highly interesting one to test, in order to find out how great may be the similarity of the two kinds of lead. In fact, wires made of radioactive lead and ordinary lead tested in the Gibbs Laboratory gave no measurable thermoelectric effect, the wires acting as if they were made of the same identical substance, although the atomic weights and densities were different. No other known case of this sort is known, so far as I am aware. The melting points of the two kinds of lead were likewise found, with the assistance of N. F. Hall, to be identified within the probable accuracy of the experiment. Let us bring all these results together into one table, so that we may better grasp their combined significance. Summed up in a few words, the situation appears to be this: At least two kinds of lead exist: one, the ordinary metal disseminated throughout the world, in non-uraniferous ores; another, a form of lead apparently produced by the decomposition of uranium, radium being one of the intermediate products. If we leave out of consideration the probably inessential difference in radioactivity, the two Since every new fact concerning the behavior of the elements gives a new possible means of discovering something about their nature, and since these facts are of especially significant kind, the anomaly is of more than passing interest, and may be said to constitute one of the most interesting and puzzling situations now presented to the chemist who looks for the deeper meanings of things. Many new queries arise in one's mind from a study of the data. Among them is a question as to the nature of ordinary lead, which possesses a less reasonable atomic weight than the radioactive variety. Why should this state of things exist? Ordinary lead may be either a pure substance, or else a mixture of uranium-lead with lead of yet higher atomic weight, perhaps 208. The latter substance might be formed, as 5 For the sake of better comparison, all the results given are those obtained at Harvard. No results of experiments elsewhere are inconsistent with these. Soddy points out, if thorium (over 232) lost six atoms of helium, and he and Hönigschmid have found quantitative evidence of its existence in thorium minerals. After reviewing all the data, Professor F. W. Clarke has brought forward an interesting and reasonable hypothesis explaining the difference between the several kinds of lead. He points out that whereas we have every reason to believe that uranium and thorium lead are the results of disintegration of heavier atoms, ordinary lead may be imagined to be the product of a far earlier synthesis or evolution from smaller atoms. The hypothesis might be supported by the analogy of the synthesis and decomposition of organic substances, which by no means always follow similar paths; it seems to be consistent with most, if not all, of the facts now known. On the other hand, may not the uniformity of ordinary lead and its difference from either of the radioactive leads be almost equally capable of interpretation in quite a different fashion? Whenever, in the inconceivably distant past, the element lead was evolved, it is hardly to be supposed that uranium-lead and thorium-lead could have been entirely absent. The conditions must have been chaotic and favorable to mixture. When the two or more forms were mixed, none of the processes of nature would separate them. Therefore they must appear eons afterwards in an equably mixed state on earth, constituting our ordinary lead. There may have been more than two forms of lead; but two forms, one possessing an atomic weight 206 and the other, an atomic weight over 208, would account for all the facts. The identity in nature of all the common lead on earth might indicate merely that one time all the matter now constituting the earth was liquid or gaseous in violent agitation, so that all the kinds of lead were thoroughly commingled before solidification. This explanation, if it could be confirmed, would furnish important evidence concerning the early history of planets. So far afield may a difference in weight amounting to two units in the twenty-fourth decimal place, between two kinds of atoms so small as to be far beyond the possible range of our most piercing means of actual observation, carry the inquiring investigator! The true answers to these questions are not to be found by speculation, such as that just detailed, however suggestive such speculation may be. They are to be found by careful observation. For example, the doubt as to the nature of ordinary lead can only be decided by discovering whether or not it may be separated into two constituents. Since weight (or mass) is the quality distinguishing between the several isotopes or kinds of lead, weight (or mass) must be made the basis of separation. Hence the only hope of separating isotopes of lead lies in the method of fractional diffusion, as has been already suggested by many other experimenters on this subject. Promising preliminary experiments preparatory to such an undertaking have already been begun at Harvard, and before long more light may be obtained. The idea that other elementary substances also may be mixtures of two or more isotopes has been advanced by several chemists. Especially if ordinary lead should really be found to be thus complicated, many, if not all, other elements should be tested in the same way. The outcome, while not in the least affecting our table of atomic weights as far as practical purposes are concerned, might lead to highly interesting theoretical conclusions. How can such remote scientific knowledge, even if it satisfies our ever-insistent intellectual curiosity, be of any practical use? Who can tell? It must be admitted that the relationship is apparently slight as regards any immediate application, but one can never know how soon any new knowledge concerning the nature of things may bear unexpected fruit. Faraday had no conception of the electric locomotive or the power-plants of Niagara when he performed those crucial experiments with magnets and wires that laid the basis for the dynamo. Nearly fifty years elapsed before his experiments on electric induction in moving wires bore fruit in a practical electric lighting system; and yet more years before the trolley car, depending equally upon the principles discovered by Faraday, became an everyday occurrence. At the time of discovery, even if the wide bearing and extraordinary usefulness of his experiments could have been foreseen by him, they were certainly hidden from the world at large. The laws of nature can not be intelligently applied until they are understood, and in order to understand them, many experiments bearing upon the fundamental nature of things must be made, in order that all may be combined in a far-reaching generalization impossible without the detailed knowledge upon which it rests. When mankind discovers the fundamental laws underlying any set of phenomena,these phenomena come in much larger measure than before his control, and are applicable for his service. Until we understand the laws, all depends upon chance. Hence, merely from the practical point of view, concerning the material progress of humanity, the exact understanding of the laws of nature is one of the most important of all the problems presented to man; and the unknown laws underlying the nature of the elements are obviously among the most fundamental of these laws of nature. Such gain in knowledge brings with it augmented responsibilities. Science gives human beings vastly increased power. This power has immeasurably beneficent possibilities, but it may be used for ill as well as for good. Science has recently been blamed by superficial critics, but she is not at fault if her great potentialities are sometimes perverted to serve malignant ends. Is not such atrocious perversion due rather to the fact that the ethical enlightenment of a part of the human race has not kept pace with the progress of science? May mankind be generous and high-minded enough to use the bountiful resources of nature, not for evil, but for good, in the days to come! THEODORE W. RICHARDS. HARVARD UNIVERSITY PROCEEDINGS OF THE BALTIMORE THE seventy-first meeting of the American Association for the Advancement of Science was held at Baltimore from December 23 to 28, and in view of the unusual conditions it has been a decided success. It will be remembered that the meeting place was changed from Boston to Baltimore, partly because war conditions had brought together at Washington scientific men from all over the country, and it was planned to have a brief compact program devoted to war issues and topics more intimately pertinent to the immediate welfare of the country. While it was not feasible to have the meetings in Washington, it was thought that members in Washington might be able to attend meetings at Baltimore, but a short distance away. With the sudden termination of hostilities the problems confronting the scientific workers have to a large extent either suddenly changed their nature altogether or have been considerably modified and, although but a short time has intervened since the signing of the armistice, the nature of the contributions and discussions in the various meetings shows a quick recognition and adjustment to these changed conditions. The rapid release of men by demobilization and the prevalent less congested conditions as to university buildings and hotel accommodations have apparently been partly responsible for the surprisingly large enrollment. The opening meeting at McCoy Hall on the evening of December 26 had an attendance of about four hundred people, and the total registration for the week was seven hundred and twenty-eight, which did not include some of the members of the various affiliated societies. At the opening meeting Dr. Edward L. Nichols announced that the address of the retiring president of the association, Dr. Theodore W. Richards, on "The Problems of Radioactive Lead" would not be given, Dr. Richards being unable to attend the meeting on account of illness. Dr. Nichols then introduced the president-elect, Dr. John M. Coulter, who in turn presented President Goodnow, of the Johns Hopkins University. In his address of welcome Dr. Goodnow spoke as follows: It is my privilege on behalf of the Johns Hopkins University to bid you welcome here to-night. It has been a great pleasure for us to feel that we have been able even in a small way to be of service to you on the occasion of this meeting. It is always an honor for a university to cooperate with the association. But, at the present time, it is peculiarly gratifying to have the opportunity of testifying to the worth of the work which men of science have been and are now doing. Science has within the past few years assumed perhaps a greater importance than it has ever before had, or, at any rate, the accomplishments of science have bulked larger in the public eye than heretofore. The struggle which has just closed has probably made greater demands on the scientific man than have ever hitherto been made. Science has, indeed, been forced to become the servant of Mars. The great war has called upon men of science to devise new weapons of both offense and defense. Without their efforts it would have been a very different conflict from what it has been. The ruthlessness with which our knowledge of scientific law has recently been applied to the destruction of life and property has, I am afraid, however, caused not a few to entertain a certain amount of apprehension as to the effects upon human life of scientific training. If a greater scientific knowledge is to bring with it the will to use that knowledge as it has been used during the past four years, civilization, which has been the product of so many centuries of human endeavor, would seem to have a perilous future. Such apprehensions are, however, I am sure, quite unfounded. Science, it is true, is in large measure unmoral. It has to do with natural law rather than with human relationships, and it is with human relationships that morality is concerned. Knowledge, of course, is power, and power or might is not necessarily right. We are told, it is true, that man can not live by bread alone. But that is not to say that he does not live at all by bread. He must have bread and he must have science. We must, so long as we live, attempt to increase our knowledge. We must endeavor through science to acquire power, to conquer Nature, to learn from her how best we may live. But that endeavor need not prevent us from at the same time striving to live well-ordered lives, to form a social organization in which right relationships shall be established, in which right rather than might shall be controlling. We may at the same time search for truth and labor for the adoption of ethical standards in accordance with which our knowledge of science may be applied. I have said that in no period in the past has science assumed such importance as in the last four years. I may add that the rôle of science in the immediate future will be of even greater significance. In the period of reconstruction upon which we are now entering, science will be called upon to bind the wounds of a bleeding world sick almost unto death. It must in some way show us how to increase production in order that we may feed the starving, house those without shelter, and clothe the naked. Never before have the demands upon the scientific man been so insistent as they soon will be. And fortunately they will be demands which he can meet without any secret lurking thought that his success will be followed by sorrow and misery. He can rejoice in the belief that his efforts will bring comfort to many whose lot has been hopelessness if not despair. For this reason I congratulate you men of science upon the opportunity which now presents itself. We are living in a very different world from that which existed only four years ago. Old traditions have been cast aside. New standards are in process of adoption. Great impetus has been given to the belief in the necessity of scientific research. I wish you all success in this, your first meeting in the new era upon which we are just entering. In behalf of the Association the response to President Goodnow's welcome was made by Dr. Coulter, as follows: In behalf of the association, I wish to express Gur appreciation of the greeting extended by President Goodnow. Johns Hopkins University is a peculiarly fitting place for a meeting of the American Association, for historically it is our first research university, an example and a stimulus to the other universities of the country. Those of us who are older can recall the distinguished names that brought to Johns Hopkins its prestige in research. President Goodnow has characterized science as a power let loose for destruction during the late war, a giant that has discovered its strength. Everything depends upon how the power is applied, but I am sure that science prefers to apply its strength in public service rather than in destruction. The great war has been called a war of science, but I trust that this kind of service that science has been called upon to render is but a prelude to a recognition of the fact that the progress of a peaceful civilization is also based upon scientific research. Speaking for this association, I am sure that we are ready to pledge ourselves to use our science in constructive work, for the advancement of knowledge and for the public welfare. In accordance with the present constitution, notice was served by Dr. Edward L. Nichols that a revised constitution and by-laws will be presented next year to be voted upon, the principle changes being those of increase in the number of sections and a condensation in form of the present constitution. Meeting in affiliation with the association were twenty-one other organizations, as follows, many of these affiliated societies having certain sessions in conjunction with corresponding sections of the association: American Federation of Teachers of the Mathematical and Natural Sciences, American Physical Society, Optical Society of America, American Metric Association, Society of American Bacteriologists, American Society for Horticultural Science, Society of American Foresters, School Garden Association of America. Two of the affiliated societies met on Monday and Tuesday in advance of the opening meetings of the association: The School Garden Association of America and the American Phytopathological Society, the sessions of the latter organization continuing till Saturday. The various meetings were held in Gilman, Hall, the Civil Engineering Building, and the Mechanical and Electrical Engineering Building, at the splendid new site of Johns Hopkins University at Homewood, towards the northern part of Baltimore, and the accommodations for the meetings of the various societies and sections were found to be convenient and amply sufficient. Inexpensive and ample lunches were provided in the Mechanical and Electrical Engineering Building. There were held perhaps the usual numbers of dinners and smokers, at which addresses of retiring presidents, invitation papers, or other interesting features were presented. The Phytopathological Society had a dinner on Wednesday evening and the Ecologists an informal dinner on Thursday evening, while after the opening session of the association, the biologists gathered for an informal smoker. On Society for Promotion of Engineering Education, Friday evening, dinners were held by the Geological Society of America, Association of American Geographers, Paleontological Society of America, American Society of Naturalists, American Society of Zoologists, American Association of Economic Entomologists, American Anthropological Association, botanists, the American Metric Association, the American Society for Horticultural Science, while the Society of American Foresters had a smoker and "Round Table Talks." On Saturday night the American Society of Naturalists held a dinner, at the close of which Vernon L. Kellogg was to have spoken on "The German Philosophy of the War" but was detained in France. The annual dinner of |