intra-uterine growth aside from its function as a transfer system. FREDERICK S. HAMMETT, COLLEGE OF PHYSICIANS AND SURGEONS, LOS ANGELES, CALIF. THE EFFECT OF DRAINAGE ON SOIL ACIDITY FOR the purpose of studying the effect of drainage on soil acidity, samples of soil were taken in October, 1916, from three of the experiment fields of the Purdue Agricultural Experiment Station. These fields are located near Westport, North Vernon and Worthington. The soils of these fields are all heavy silt loam, very low in organic matter and naturally poorly drained and quite acid in reaction. All of these fields have been thoroughly tile drained from three to five years. A portion of the Westport field is undrained and there are adjacent undrained, untreated areas alongside the North Vernon and the Worthington fields. Table I. shows the acidity of the soil as determined by the potassium nitrate method. Without entering into a discussion of the merits of different soil acidity methods, it may be said that on these soils, which are low in organic matter, there is no great difference in the degree of acidity shown by this method and the lime water and calcium salt methods. These results are consistent enough to indicate that drainage has a material influence on the acidity of soil of this type. Farmers often refer to wet, poorly drained land as sour. While agricultural writers have placed little or no emphasis on such a correla tion, it is quite probable that soils in general will tend to become less acid when thoroughly drained, and vice versa; they will tend to become more acid when water-logged and poorly aerated. In testing soil acidity at different seasons of the year the results often vary quite a little in samples from the same plots of soil. These differences can not be attributed altogether to errors in sampling. The writer believes that at least part of the change of acidity is due to difference in aeration and moisture content of the soil at different seasons. Lipman and Waynick, in an investigation of the effect of climate on soil properties, report that Maryland soil, which shows an acid reaction in its original location, when transported to Kansas or to California becomes neutral or slightly alkaline. It is quite probable that the better drainage and aeration of the soil when placed under less humid conditions could account very largely for the changes in reaction. Considering SiO, an acid-forming oxide, practically all soils except those very high in the basic reacting elements, have a potentially great capacity for developing an acid reaction. The writer believes that the constitution of the silicates of aluminum has more to do with injurious soil acidity than any other single factor. The acidity of aluminum silicates varies both with the relative proportion of SiO, to ALO, and with the amount of combined water in the silicate.2 The weathering and changing of soil silicates under poorly drained or well-drained conditions would undoubtedly vary the constitution of the silicates and also vary the degree of soil acidity. It is quite true that certain types of well-drained sandy soils are acid. It is true also that a number of other factors besides drainage conditions affect soil acidity, but it is probable that the most acid soils are formed in poorly drained areas. S. D. CONNER INDIANA AGRICULTURAL EXPERIMENT STATION, LAFAYETTE, IND. 1 Lipman, C. B., and Waynick, D. D., Soil Science, Vol. I., No. 1, p. 5, 1916. 2 Conner, S. D., "Acid Soils and the Effect of Acid Phosphate and Other Fertilizers upon Them,'' Jour. Ind. and Eng. Chem., Vol. VII., No. 1, p. 35, 1916. SCIENCE RADIATION AND MATTER1 WE must congratulate ourselves upon the fact that we have been able to listen to such clear, concise and accurate presentations of the most fundamental problems that lie before pure science to-day. I would like, also, to extend to the speakers our sincere thanks for their efforts in giving us such interesting expositions of these abstruse theories. It is my privilege to open the discussion on radiation and the structure of matter. Modern theories of radiation are largely concerned with Planck's conception of the radiation of energy in quanta, and with the extraordinary action constant usually denoted by the letter "h." I would like to present for your discussion some ideas on the relations between the high frequency vibrations which we observe in general Xradiation, and the forces holding the electrons and atoms together, including a physical conception of what this constant "h" really means. Instead of basing the discussion on the conceptions of entropy, and thermo-dynamic probability, I shall start from our recent experiments on general X-radiation. Before we learned from experiments that X-rays had definite wave-lengths, people supposed that they had, and that we could calculate their frequencies by the formula kinetic energy equals hv. We have shown, by experiments at Harvard, that this equation is not, in general, true, but that it does hold for particular cases. Mr. Hunt and I investigated the general X-radiation from a Coolidge tube, excited by a high potential constant voltage storage battery, using an X-ray spectrometer, and found that although the effective, or average, frequency does not obey the law represented in the equation (1), the equation does give the maximum frequency obtainable with a given electron energy. Dr. Webster then examined the characteristic X-radiation, and discovered that the kinetic energy of the electrons required to produce the alpha and beta lines of the K series is larger than is represented by equation (1), but that the gamma line (the highest frequency line in this series) approximately obeys the law. It appears, therefore, from our experiments, that equation (1) gives the maximum frequency of the radiation due to an electron's hitting an atom, but does not, in general, mean that the entire amount of the electron's energy is radiated at frequency v. I have recently shown that it is not necessary to assume that energy is radiated in quanta "h" in order to deduce equations for the distribution of energy in emission spectra similar to the equations representing black body radiation, so that we are not compelled to believe that because Planck's radiation law fits the facts of black body radiation more or less closely, therefore energy must be radiated in quanta hv. In attempting to explain why this constant "h" enters into the radiation law and in seeking for a physical conception of the mechanism of radiation, we are not therefore compelled to explain the emission of radiation in quanta hv, but rather the fact that an electron with a given kinetic energy, when it hits an atom, can produce radiations of frequency up to but not greater than that given by equation (1). This is the fundamental fact that needs explanation. According to the modern conception of the constitution of matter, an atom possesses a complicated electro-magnetic structure in which the electrons play an important rôle. The electro-magnetic forces in this structure are greater near its center than at the periphery, and therefore the high frequency vibrations of the electrons must be associated with parts of the atom near its center. Hence, the reason why an electron can not produce a high frequency radiation unless it possesses a certain kinetic energy lies in the fact that it does not penetrate far into the atom unless it has a sufficient speed. This presupposes a force of repulsion between the electron and the atom. The theory of atomic structure seems to demand such a force in order to explain why atoms do not collapse; so that we have confirmation of the existence of such forces from two sides: the radiation and the structure of matter. The Before discussing further the nature of this force and the laws it must obey, I would like to present to you a conception of the difference between line spectra and the general, or continuous spectra. frequencies of the characteristic lines depend upon the nature of the atoms struck by the electrons, whereas the frequencies of the general radiation depend upon the kinetic energy of the electron that does the striking. This suggests that the characteristic lines are due to vibrations of parts of the atoms themselves (of electrons in the atoms, for instance) whereas the general radiation or continuous spectrum is due to the vibrations of the electrons that hit the atoms. The question now arises "How can an electron vibrate with all possible frequency so as to give a continuous spectrum?" The electron moves in the strong electromagnetic field of the atom, and when an From this equation it appears that the frequency is independent of the velocity of the electron and of the radius of the spiral and that it is practically proportional to the strength of the magnetic field; and since H varies continuously, the frequency can have all possible values (up to a maximum), which gives the radiation the character of a continuous spectrum. Let us combine this conception of general X-radiation with the experimental fact that the maximum frequency due to the impact of an electron against an atom is given by equation (1). Suppose the electron to be traveling very nearly along the line of force coming from a very great distance, where its velocity is v and let z be its distance from any fixed point at the time t; let F be the total force acting on the electron in the direction of the weaker magnetic field. Then we can show easily Then we can show easily that THE RELATIONS OF MAGNETISM TO MOLECULAR STRUCTURE MAXWELL'S classical theory of electricity and magnetism contributes little to our knowledge of molecular structure. For the portion of it which deals with material substances is exhibited in terms of quantities for which the process of definition wipes out structural distinctions. It is only through molecular theories of magnetism that magnetic phenomena may be correlated with molecular structure. Langevin's theory of magnetism appears to be the soundest attempt to formulate such a theory. He hypothecates the existence in the molecules of every substance of groups of electronic orbits which by virtue of the peculiarities of the structure of the molecules may be so arranged that the resultant magnetic field due to the electronic orbits in a given molecule at points without the molecule may or may not vanish. In the former case the molecule is diamagnetic, in the latter magnetic. The effect of the application of a magnetic field to a diamagnetic substance is to change the orbital velocity of any electron. This change is in the proper direction to account for the diamagnetic polarity of the substance. Langevin's theory leads to an expression for diamagnetic susceptibility which does not involve the temperature, in agreement with Curie's law for diamagnetism. Numerous exceptions to this law exist, but the exceptions may probably all be taken care of by a slight extension of Langevin's theory as proposed by Oxley. One of Oxley's most interesting conclusions is that the mutual magnetic field of two diamagnetic molecules in intimate contact is of the order of 10' gausses. Langevin's hypothesis, while probably the most satisfactory yet advanced, leaves us quite in the dark as to a mechanical explanation of the architecture of the molecule. In paramagnetic and ferromagnetic substances in accordance with the views of Langevin the rôle played by the molecule is not as in diamagnetic substances independent of the molecule's orientation in space, and it is necessary to assume that the effect of an applied field is to rotate the electronic orbits so that the direction of the resultant external field of a molecule tends toward that of the applied field. But the theory tells us nothing of the mechanism which will account for this orientation. Resisting the orientation will be heat agitation and perhaps inter-atomic and molecular actions of other than magnetic type. In a paramagnetic gas the resistance to orientation is supposed to be entirely due to heat agitation. The theory for such a gas leads to an expression for the susceptibility which depends upon both the impressed field and the temperature, but for fields attainable in the laboratory the susceptibility varies inversely with the absolute temperature in accordance with Curie's law for paramagnetism. With the aid of the assumption that as regards rotation the molecules of a paramagnetic liquid behave like those of a paramagnetic gas it is possible to extend the theory of the gas to include that of the liquid, and such an extension is probably reasonably safe for liquids not given to polymerization. In Weiss's theory of ferromagnetism it is assumed that, so far as rotation is concerned, the molecules of a ferromagnetic substance behave like those of a paramag netic gas, a somewhat questionable assumption in this case. The effect of neighbor ing molecules upon a given molecule is assumed to be that which would be produced by a very large localized magnetic field of the order of 10' gausses. The theory based on these assumptions succeeds to a remarkable extent in explaining many of the facts of ferromagnetism. The large internal fields hypothecated by Weiss and by Oxley are to be regarded as devices for averaging out in a measure the complicated effects due to molecular structure. Through experiment Weiss was led to belief in the existence of an elementary unit of magnetic moment which he called the magneton. This corresponds in electrical theory to the electron. In many instances the magnetic moment per molecule appears to be very nearly an integer number of magnetons. But the evidence is not weighty enough to justify the acceptance unreservedly of this proposed new physical unit. The subject of magneto-chemistry is already a very extended one. Here the attempt is made to establish a connection between the magnetic moment of a compound and those of its constituents, and additive relations are sometimes found. Substantial chemical information is often found through magnetic analysis. Various attempts have been made to explain chemical valency bonds through the magnetic attractions of rotating electrons in the atoms. One of these, that of Parsons, offers promise of considerable success in this direction. The recent magnetic experiments of Barnett and of Einstein and deHass appear to prove definitely the existence of electrons rotating in closed orbits within the molecules of material substances, and thus furnish important support to Langevin's fundamental assumptions. From this necessarily inadequate discus |