as it should have been. It, of course, was impossible, or rather impracticable, to extend a precise level net into areas through which railroads had not been run, for the expense would have been prohibitive. It may be that the Survey did not fully realize the necessity for having all engineering and surveying work on the same datum, but in recent years it has become fully alive to the necessity of having a single datum for the entire country, and it is consequently extending its precise leveling net as rapidly as funds available will permit.

While it is of value to the nation for various organizations and individuals to adopt and use mean sea-level datum for their elevations, the country will benefit still more if each organization doing extensive leveling will publish in pamphlet form the elevations and descriptions of the bench marks they may establish in order that other organizations and individuals may properly coordinate their levels. Engineers are urged also to use substantial bench marks in order that future work may be benefited by their preservation.

The amount of precise leveling which should be done by the federal government can not be foretold. It must depend upon the needs of the various organizations and individuals using the results. After a certain development of the precise level net which appears now to be absolutely necessary, the rapidity with which further extensions are made should depend upon the development of the country. But such further extensions should precede rather than follow such development, as is proved by the unfortunate condition of affairs in much of our engineering and surveying work, due to lack of precise elevations in the past, when such work was inaugurated.

This paper on mean sea level should, and no doubt will, do much good in furthering the universal adoption of mean sea level as the reference surface for all elevations.

The publication of such pamphlets by government organizations is to be commended, for they present facts to the public in an effective way which may otherwise be buried for years in valuable but more cumbersome government reports with which all of us are more or less familiar. WILLIAM BOWIE

PROCEEDINGS OF THE NATIONAL

ACADEMY OF SCIENCES

THE sixth number of volume 3 of the Proceedings of the National Academy of Sciences contains the following articles:

The stark effect in helium and neon: HARRY NYQUIST, Sloane Laboratory, Yale University. An improvement of Lo Surdo's method is applied.

New analyses of echinoderms: F. W. CLARKE and R. M. KAMM, United States Geological Survey, Washington. A progressive enrichment in magnesia, following increase of temperature, is unmistakable.

On utilizing the facts of juvenile promise and family history in awarding naval commissions to untried men: C. B. DAVENPORT, Station for Experimental Evolution, Carnegie Institution of Washington. A study with family charts of a number of naval officers.

The triplet series of radium: GLADYS A. ANSLOW and JANET T. HOWELL, Department of Physics, Smith College.

The measurement of small angles by displacement interferometry: CARL BARUS, Department of Physics, Brown University.

Mechanisms that defend the body from poliomyelitic infection, (a) external or extranervous, (b) internal or nervous: SIMON FLEXNER, Rockefeller Institute for Medical Research. A report upon the results of recent experiments.

The occurrence of harmonics in the infrared absorption spectra of diatomic gases: JAMES B. BRINSMADE and EDWIN C. KEMBLE, Jefferson Physical Laboratory, Harvard University. The discontinuities in the structure of these bands force the conclusion that the angular velocities are distributed among the molecules in the discontinuous manner predicted by the older form of the quantum theory, and the proved existence of harmonics is almost equally good evidence that the vibrational energy of the molecules is distributed in the same manner.

The loss in energy of Wehnelt cathodes by electron emission: W. WILSON, Research Laboratories of the American Telephone and Telegraph Company and of the Western Electric Company. The emission of the elec

trons from Wehnelt cathodes is due to a similar mechanism to that causing the emission from heated pure metals.

Daily variations of water and dry matter in the leaves of corn and the sorghums: EDWIN C. MILLER, Kansas Agricultural Experiment Station. Under the conditions of these experiments the sorghums, and more particularly milo, absorb water from the soil and transport it to the leaves more rapidly in proportion to the loss of water from the plant than does corn; and thus the sorghums can produce more dry matter for each unit of leaf area under severe climatic conditions than can the corn plant.

Note on complementary fresnellian fringes: CARL BARUS, Department of Physics, Brown University.

The displacement interferometry of long distances: CARL BARUS, Department of Physics, Brown University. In preceding notes two methods for measuring small angles have been suggested. Application is here made to the determination of distances and is shown that an object at about a mile should be located to about thirty feet.

National Research Council: Meetings of the Executive Committeee and the Joint Meeting of the Executive, Military, and Engineering Committees. Report of the Astronomy Committee. EDWIN BIDWELL WILSON

MASS. INSTITUTE OF TECHNOLOGY,
CAMBRIDGE, MASS.

SPECIAL ARTICLES

INTRA-VITAM COLOR REACTIONS

WE have slowly come to have great confidence in the specificity of certain physiological actions. We introduce into an organism certain substances, and definite results follow; but about the only thing we know in the matter is that the results follow with certainty. In such cases, if only we could see what it is that happens while it is happening, it seems certain that important advances would be made in our knowledge of nutrition, growth and decayof physiology, pathology and medicine.

If substances giving color reactions in living tissues could be applied to small, transparent, varied and highly complex living or

ganisms, under circumstances that would permit microscopic examination while the reactions are in progress, we might hope for more light on this exceedingly important subject. Experiments I have made lead to the belief that many of the conditions requisite for success in this line of investigation can be much more fully realized than hitherto by feeding colored substances, notably coal-tar dyes, to free-living nematodes.

These minute, transparent animals are comparatively highly organized; not only this, but also extremely varied in their mode of life. Some are exclusively vegetarian, others exclusively carnivorous, and others omnivorous. They constitute a group composed probably of hundreds of thousands of species, embodying an almost inconceivable number of kinds of physiological action. Their organs are enclosed in a thin transparent cuticle, and are strung out so as to make them unusually suitable for intra-vitam examination. Under slight pressure the nema flattens out more or less without losing its vitality sufficiently to preclude satisfactory intra-vitam examination under the highest powers of the microscope.

Observing certain precautions, I find that a great variety of coal-tar compounds and other colored compounds can be fed to nemas, apparently without interfering materially with their normal metabolism. I have had the best results by cumulative action, using small quantities of color dissolved in the medium in which the nema lived, and allowing the dye to act for days or weeks.

Not infrequently the dyes prove to be highly specific in their action. Only certain cells, or only definite parts of certain cells, exhibit visible reactions in the form of colorations. The results obtained by the use of any given dye may be quite varied. It is evident in many cases that the dye is digested and assimilated, thereby undergoing molecular changes by which it is converted into new compounds in a manner analogous to the processes exemplified in chemical laboratories devoted to the production of aniline dyes. Thus, a dye may give rise to several different colors, none of them like that of the dye itself, and all of them very

likely due to new compounds. Often I have seen considerable evidence pointing to the conclusion that in some cases the dyes fed are converted into colorless compounds during the process of digestion (a reduction phenomenon), and these colorless compounds reconverted into colored substances after they arrive at certain destinations or conditions. The number of changes these "living laboratories " can ring on the molecular structure of a given dye must in some cases be very considerable. Two or more dyes fed simultaneously sometimes produce results more or less independent of each other. The spectacles are very brilliant.

Using these methods I have been able to demonstrate within the confines of a single cell the existence of an unsuspected number of kinds of "granules," manifestly playing different rôles. After the differences among these bodies have been shown in this way, it is sometimes possible to perceive corresponding morphological differences; but without the aid of the color reactions the differences would never have been suspected.

The main thing to bear in mind is that on the basis of our present more complete knowledge of the chemical and physical properties of coaltar-derivatives these color reactions in living nemas may be made the index of physiological characters possessed by cells and their components. In view of the great variety of the known coal-tar derivatives, and the great variety of physiological activities exemplified in the free-living nemas, it seems to me a very reasonable hope that researches directed along this line will lead to important results, and that the nemas may become classical objects in cell and general physiology, as they have already become in sex physiology.

A new and rather extensive nomenclature will become necessary. It will be needful to distinguish between the results of intra-vitam, intra-mortem and post-mortem staining; for these three terms represent as many different phases in the chemical reactions that take place during the course of the experiments. As the cells lose vitality, new color reactions occur, and the death of the cell is followed by

further equally marked changes in the reactions.

The cell elements I have mentioned vary in size, but most of them are exceedingly small, many so small that they are on the limits of visibility, using the very best instruments with the greatest skill and under the most favorable conditions. On the other hand, some of them are large enough so that they can be examined in considerable detail and their structures made out. Among them are the bodies currently referred to under the name mitochondria and other more or less synonymous words.

As it will be some time before we can establish a rational nomenclature for these numerous intracellular structures, it is desirable meanwhile to adopt terms that will permit intelligent discussion of our discoveries as they are made. While the principles underlying such a nomenclature are easily defined, it is by no means easy, in the present condition of things, to suggest suitable short and expressive roots to be used as a basis. There will be less liability of confusion if the names first employed relate to form, size and position rather than to function.

Investigations of this character are not unlikely to stimulate further research in connection with aniline derivatives. Present efforts are directed toward the discovery of dyes of greater or less permanency. Permanency, however, is of little moment in these investigations; what is of moment is the chemical composition and physical properties of the dyes. No doubt dyes of a greater range of composition can be produced if permanency be disregarded. Furthermore, as already hinted, colorless compounds may be used in intravitam work if in the course of the metabolism they are converted into colored compounds. The results of recent studies of dies as chemical indicators come into play, and give valuable evidence in determining acidity and alkalinity.

I am almost ready to express the opinion that a small army of investigators should be engaged on the problems opened up in this way. The equipment needed by the investigator is as follows: He must be a very good

microscopist, versed in physiology, cytology and histology. He should be conversant with the chemistry of the coal-tar compounds, not so much from the viewpoint of the maker of dyes as from that of the broad-minded chemist, freed from the economic domination of the dye industry, for, as before remarked, fugitive dyes, and even colorless compounds, are possible factors in such investigations as are here under discussion. He should have a working knowledge of nemas.

ILLUMINATION

In order to distinguish with accuracy among intra-vitam color reactions it is necessary to be very particular about illumination. The most perfectly corrected lenses must be used, both as condenser and objective, and the light used must be as nearly white as possible. The best source of light known to me for these researches is bright sunlight reflected from a plane matte white reflector. The reflector should be several feet across, and placed at a distance from the microscope several times its own diameter. It should be universally adjustable, so that it can be set to reflect a maximum of light to the mirror of the microscope -all the better if heliostatic. A good surface for the screen is made by whitewashing a rather finely woven cotton cloth.

slide is shown in the accompanying illustration. The substage of the microscope should have a centering arrangement and a rack and pinion or screw focusing adjustment. A little experience with an apparatus of this sort, in which all known precautions are taken to remove color from the optical system, leads one to distrust the ordinary Abbé substage condenser where fine distinctions are to be made between colors, especially if the colors are of similar character. N. A. COBB

U. S. DEPARTMENT OF AGRICULTURE

the difference in the total heat of the vapor L between the temperatures T and T-1 degrees absolute, viz., L-L, and in this case an amount of heat equal to H/T (L-L.) must be added to maintain the vapor in a saturated condition, and it is therefore called the "negative specific heat” at the temperature T. If L-L is greater than H/T the difference of heat must be added and it is then

called "positive specific heat."' The examples show that all the numerical values in this respect determined by Clausius on a somewhat different basis agree perfectly with those obtained after the above formula, which agreement, however, is not found with other results obtained by other authors on a similar basis, apparently due to errors of judgment so liable in the application of the calculus. Moreover, it is argued that instead of the heat quantity H/T which represents the net work when the expansion takes place in a reversible cycle, the heat quantity We representing the maximax work in reversible expansion should be used, which changes the values of positive and negative heat slightly.

The separation of erbium from yttrium: B. S. HOPKINS and EDWARD WICHERS. The erbiumyttrium material used in the investigation was obtained by fractional crystallization of the bromates. Methods recommended by Drossbach and Wirth could not be duplicated with the success obtained by these workers. Cobalticymide precipitation as recommended by James, was found to give a good separation, but offered practical difficulties. Precipitation with sodium nitrite as used by Hopkins and Balke found to give a rapid separation when used with material which was predominantly yttrium.

A study of the ratio of Er20:2 ErCl,: C. W. BALKE and EDWARD WICHERS. A brief discussion of other ratios used in determining the atomic weights of the rare earth elements was given and the constancy of composition of the rare earth sulphates questioned. The method of applying the oxide-chloride ratio to erbium was described and data given which give an atomic weight approximately one unit higher than the present value.

A thermal study of some members of the system Pbo-SiO2: L. I. SHAW and B. H. BALL. Many mixtures of PbO and SiO, varying in composition from 40 per cent. to 90 per cent. PbO were melted in an electric furnace and the records of their thermal conduct plotted on time-temperature diagrams. (In some cases PbO, was used instead of PbO and its behavior is noted.) The significant temperatures of these graphs were then combined

into a composite temperature and it was concluded that the system is a case of solids in solid solution. Two maxima corresponding to the composition PbO-Sio, and 2 PbO-SiO, were found and another 2 PBO-5 SiO, was clearly indicated. Two eutectics are indicated, though the lower one may be a transition point of the one of the higher melting point. As noted by previous investigators, a transition point of SiO, was found at 540°580° C. All mixes sintered at 690° 10° C.

A study of the change of conductivity with time in the system methyl alcohol-iodine-water: L. I. SHAW and JOHN P. TRICKEY. Conductivities of solutions of iodine in methyl alcohol of various boiling points have been measured. It was found that the conductivity increased much more rapidly in the case of the solutions in alcohol of higher boiling points; also, that the conductivity reached a higher value in the case of the solutions from the higher boiling point alcohols. It was suggested that this was probably due to the water content of the alcohol. It was found that a smooth curve could be drawn through the points at which the conductivity of the various solutions became constant. Suggestions as to the probable reaction were given.

The solubility of pure radium sulfate: S. C. LIND, C. F. WHITTEMORE and J. E. UNDERWOOD. The solubility of RaSO, in water and other solutions is of practical interest since all processes for the recovery of radium from its ores involve, at some stage, the precipitation of radium together with barium as sulfate.

Studies in pseudo-isotopy-Part I: S. C. LIND. Experiments of the author and others have shown that when radium and barium are partially precipitated from a solution containing a mixture of the two, no change in relative concentration takes place. This is true for sulfate, oxolate, carbonate, and perhaps all other difficulty soluble salts, and bears an exact analogy to the inseparability of the isotopic elements. The fact that radium and barium are only pseudo-isotopic, however, is shown from the great divergence of their atomic numbers, and their ready separation by recrystallization of the chlorides or bromides. It has been shown in the preceding paper that the assumption of identical solubility of RaSO, and BaSO, in analogy to their pseudo-isotopic action in precipitation reactions, is far from the truth. Conversely, this must raise the question, from the purely experimental side, as to the truth of the assumption generally made of identical solubility of true isotopes.