from western Tennessee to southern Ohio where the snow was deep at the time. One Weather Bureau observer in West Virginia reported a minimum of 37° F.; and another in Iowa, -40°. Extreme minima, -45° F., established new low records for South Dakota and Maine. On January 12, "that cold Saturday," a true blizzard with snow driven by a gale at a temperature down to 20° below zero (F.) tied up traffic almost completely for two days in the Middle West.

Relative to the cold land or snow surfaces, the open waters of the Great Lakes, Atlantic and Gulf were excessively warm; therefore they favored the development of numerous cyclones-some of them very intense. These supplied the snow which blockaded the railroads, or the rain which produced such disastrous floods in the ice-gorged rivers.2 In the immediate vicinity of the Great Lakes, snow fell almost daily in January; and with many heavy falls, reached totals of 3 to 5 feet in that month alone. Chicago with 42 inches and Milwaukee with 53, saw the worst snow conditions in their histories. Farther south, in a belt from the Ozarks to the upper Ohio River, equally large amounts of snow were precipitated in January by the cyclones passing on the south, around the edge of the cold snow blanket. October and December were snowier than usual, especially December, in much of the eastern half of the country.

The weather was extraordinary not alone in the eastern United States: west of the Rockies the winter was one of the warmest on record. Extreme dryness prevailed in the southwest; but extraordinary rainfall occurred in the northwest. In December a temperature of 86° below zero (F.) was reported from the Upper Yukon, at the mouth of the Pelly River. If authentic, this established a record for North America which is only 4° (F.) below the earth's extreme surface minimum - 68° C. (-90.4° F.), observed in Siberia in 1892.3 Northern Sweden at about the same

2 See Mo. Weather Rev., Feb., 1918.

8 See note, "The Lowest Air Temperature at a Meteorological Station," Mo. Weather Rev., Vol. 45, 1917, pp. 407-408.

time had unprecedented coldness —57° C. (— 70.6° F.) at Asele, and reports from Spain, central plateau of France and southwestern Asia tell of a winter of extreme severity.

Why is the world having such unusual weather? This is a period of sun-spot maximum-a time when solar radiation comes to its maximum; a condition occurring on the average once in 11 years. Experience has shown that at such times there is a general tendency in winter to strong continental anticyclones and ocean cyclones; with corresponding storminess and coolness.5 For North America, a strong winter anticyclone generally seems to favor coldness in the east and warmth in the west. Locally, the snowiest and coldest weather occurs where, in spite of low temperatures, the supply of moisture is abundant and the temperature contrasts produce the storminess requisite to precipitate it as snow. Then this snow keeps the air cold and helps to make more snow; until important changes in general winds dominate the weather and eliminate the snow-cover-as was the case early in February, 1918. While the present degree of solar activity lasts, further occurrences of extreme weather are not unlikely.

in

METEOROLOGY IN THE ARMY AND NAVY SINCE weather has much to do with military operations, especially flying, it was natural that before one month had passed after the entry of the United States into the war, structors had been sent to the flying school at Toronto for preparation to teach meteorology at the six new aviation ground schools in the United States. This work has progressed quietly ever since. Professor R. DeC. Ward,

4 For a further discussion, see C. G. Abbot, "The Sun and the Weather," The Scientific Monthly, Vol. 5, Nov., 1917, pp. 400-410.

5 Cf. H. Arctowski, Bull. Am. Geog. Soc., 1916, Vol. 42, pp. 270-282.

6 See T. A. Blair, "Some Temperature Correlations in the United States," Mo. Weather Review, Vol. 45, 1917, pp. 444-450.

7 Cf. R. DeC. Ward's most recent articles, Scientific Monthly, February and April, 1918; and in Jour. of Geography.

the instructor in aeronautical meteorology at the U. S. Army School of Military Aeronautics at the Massachusetts Institute of Technology, has published a syllabus of his course of ten lectures, and also the essentials of these ten as condensed into three lectures. This presentation of "Meteorology and War-Flying" gives the essence of what the aviator needs to know, and contains full references to this rapidly developing application of meteorology. Major (formerly Professor) Wm. R. Blair has prepared a report on "Meteorology and Aeronautics,"10 the purpose of which is "to show the sort of atmospheric data available and to put the subject in such shape as may make it bear directly on the problems which are met in aviation."

While the aviators were being trained, the Signal Corps was establishing its meteorological service abroad. As the first contingents of the American Army went overseas, Majors W. R. Blair and E. H. Bowie, appointed respectively from the aerological and forecasting divisions of the Weather Bureau, were put in charge of the meteorological work. In November those responding to a call for a large number of meteorologists were given a period of intensive training at more than a score of Weather Bureau stations. Professor W. J. Humphreys's new book, "The Physics of the Air," which is being published in the Journal of the Franklin Institute, was of great help to the more advanced students. This work is a highly valuable contribution to the science, for it covers the fundamentals of meteorology in such a way that it can be used readily as an advanced text-book.

More meteorologists are needed. So a Signal Corps School of Meteorology has been established at College Station, Texas. Here over 300 meteorologists, physicists, engineers and other technical specialists are about to begin an 8-week course in meteorology. Dr. Oliver

8 SCIENCE, July 27, 1917, Vol. 46, N. S., pp. 84-85.

Mo. Weather Rev., Washington, December, 1917, Vol. 45, pp. 591-600.

10 Report No. 13, 1917, National Advisory Committee for Aeronautics, Washington, D. C.

L. Fassig, from the Weather Bureau at Baltimore and Johns Hopkins University, is chief instructor. There are to be three assistant instructors: Mr. W. T. Lathrop, from the Weather Bureau at Greenville, S. C., for instruments, observations and map-making; Lieutenant Wm. S. Bowen, for the aerological work; and Dr. C. F. Brooks, from Yale University, for the course in general meteorology. About thirty of the Weather Bureau men in the school will also assist in instruction.

In addition to this training of specialistsand perhaps induced thereby-are the short courses in meteorology included in the military instruction of the Reserve Officers Training Corps in many universities.

Meteorology in the navy has been developed by Lieutenant Commander Alexander McAdie, in charge of the aerographic section, and trained men are in service overseas and in this country. A school for men taking up this work is maintained at Blue Hill Meteorological Observatory under the guidance of L. A. Wells, chief observer and forecaster of the observatory.

Naval training units at the universities, are now, or will soon be, receiving instruction in marine meteorology.

The importance of meteorology has never before received such wide recognition, and in view of the permanent development of aeronautics, it seems safe to predict that hereafter it will always hold a more important position in the curricula of the universities.

COLLEGE STATION, TEXAS

CHARLES F. BROOKS

SPECIAL ARTICLES

CONCERNING SELECTIVE PERMEABILITY

In most cases in living organisms, cell permeability does not even seem to violate the known physico-chemical laws. There are, however, several exceptions, notably in the intestines and kidneys, where the permeability is selective.

In considering the membranes that seem to disturb osmotic laws, it is often stated that they cause these disturbances because the

membranes are living, as though that were sufficient explanation. Are not the membranes that do obey the laws living, too? Those membranes through which certain substances can pass from a lower to a higher concentration are very probably different from the membranes used in experimental work. It is only by assuming that the membrane plays an active part in determining this one-sided permeability that the thermodyamic laws are brought into question. The sieve theory, even when so modified as to render negative osmosis1 available, does not seem convincing. No gradation of molecules in the membrane, either of concentration or kind, allowing the solute to pass from one molecule to another, could possibly explain the facts. Nor does the theory of the funnel-like arrangement of lipin molecules,2 ingenious though it be, allay one's curiosity. However, there is no doubt that most of the recent ideas on this question have been correct in postulating structures as a necessity in any explanation of this elusive (vitalistic) phenomenon.

Wherever selective permeability occurs there is at least one layer of cells through which the solute has to pass. It is inconceivable that if all parts of these cells were exactly alike there would be selective action. But there seems to be no theoretical difficulty provided certain differences exist. The two membranes in contact with the two fluids need to be different. The substance under consideration easily passes the membrane on the entering side of the cell, but passes either not at all, or with great difficulty the membrane on the exit side of the cell. In the cell a chemical change occurs in the substance that has entered. After this change it can pass the second membrane easily, but passes only with difficulty the membrane by which it gained

entrance.

It is not necessary to assume a profound change to make conditions favorable for this differential solubility. But it is necessary that the substance formed should exist in

1 F. E. Bartell, J. Am. Chem. Soc., 36, 646 (1914).

2 T. B. Robertson, SCIENCE, 45, 567 (1917).

higher concentration than the original substance when the two are in equilibrium. A change from an alkaline to a neutral or acid medium, involving a change from a sodium salt to the free compound or to, say, the chloride would be sufficient, or a synthesis of the entering compounds to more complex ones would suffice to make the theory plausible.

Because of our ignorance of just what happens in these membranes and cells, it can not be stated with certainty that specific changes do occur in a substance on passing through the cells and membranes. But the conditions necessary for such chemical and physical alterations seem to exist. The probabilities in this hypothesis can be more readily appreciated by taking an example.

The fats are hydrolyzed in the intestines to the sodium soaps. These sodium soaps, but not the fats, are able to pass the intestinal wall membrane. On entering the cell space inside the wall, the soaps are not free to pass on to the lymph or blood, because of the comparative impermeability of the second membrane to the soaps. While between these two membranes the soaps are synthesized to fats by the aid of enzymes in the presence of glycerol. Now these fats are able to pass through the second membrane to the lymph or blood; but the membrane on the intestinal side is comparatively impermeable to the fats. It is thus evident that there is reason for much higher concentration of fat in the lymph than in the intestines.

Though this illustration was chosen because it fits the theory, there is no inherent reason why the same conditions should not apply, say, to the absorption of the amino acids. They may be absorbed by intestinal cells as the sodium salts, then be changed to free amino acids, and pass thus to the blood. It is not necessary to assume that the compound exists in the same form in the blood as in the intestinal cell. It may change to any conceivable compound after passing the second membrane, may even change back to the one that passed the first membrane. There is more difficulty in accounting for the selective permeability of membrane cells in the case of rather

inert chemical substances, such as the passage of sugars through the intestines or of urea through the kidney. But no decided changes in the molecules seem necessary. The conditions in the membrane cells may be favorable for weakly combined synthetic derivatives with the right solubilities. When we realize how susceptible to small differences in salts the membranes are, it is not impossible that some particular salt of the passing substance may be all that is necessary to determine its ready exit. If all other ideas fail in any given case, one can always fall back on the everready help of the all-pervasive enzyme.

Several other writers have stated that these selective membranes behave as though a genie stood at the opening in the membrane, allowing the molecules from the side of lower concentration to pass, while closing the door to those moving in the opposite direction. It is evident that a space in which the proper chemical reaction occurs, and which is situated between the two different membranes with the proper permeabilities, functions like our anthropomorphic genie.

It is rather apparent that the idea outlined above is about half way between that of ordinary permeability and secretion. Though it does have many points in common with secretion, it seems wise not to confuse the two; for it is clear that they are different in the purpose served as well as in the method of obtaining their results.

If the attention is confined to the isolated system, solution one, the cell membrane as a whole, and solution two with concentration greater than solution one, the law of the conservation of energy is not obeyed. This might be urged as evidence of vitalism. But closer scrutiny will show that the necessary energy to run this system comes from outside. The substance necessary for the chemical reaction has to be formed and sent to the proper place. If this substance is derived from solution two directly, energy equivalent to that produced in the combination must be supplied to dissociate the complex. And energy is necessary to transport this substance back again to the permeability cell. Energy is also consumed in

maintaining the cell structure. Even in a living organism one hesitates to start a perpetual motion theory, partly because it is such a lazy way of settling a difficulty, and partly because it would necessitate a later disillusionment. C. G. MACARTHUR

MEDICAL SCHOOL,

STANFORD UNIVERSITY

THE AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE

SECTION B

THE section convened at Pittsburgh at 10 A.M., December 27, 1917, in Room 209 of the School of Applied Science, Carnegie Institute of Technology. Its sessions, jointly with those of the American Physical Society, extended over a period of three days. The scientific papers presented under the auspices of the American Physical Society are as follows:

"The optical properties of rubidium," by J. B. Nathanson, Carnegie Institute of Technology.

by

"A preliminary study of the luminescence of the uranyl salts under cathode ray excitation, Frances G. Wick, Vassar College, and Louise S. McDowell, Wellesley College.

"Note on a phosphorescent calcite," by E. L. Nichols and H. L. Howes, Cornell University.

"The visibility of radiation in the blue end of the visible spectrum," by L. W. Hartman, University of Nevada (communicated from the Nela Research Laboratory, Cleveland).

"An improved form of mercury vapor air pump," by Chas. T. Knipp, University of Illinois.

"Heat conductivity of cerium," by C. N. Wenrich and G. G. Becknell, University of Pittsburgh. "Temperature and heat of fusion," by J. E. Siebel, Chicago.

"Report on the construction of certain mathematical tables," by C. E. Van Orstrand, U. S. Geological Survey, Washington, D. C.

"Mobilities of ions in vapors," by Kia-Lok Yen, University of Chicago.

"The size and shape of the electron," by Arthur H. Compton, Westinghouse Lamp Company.

"The coefficient of emission and absorption of photo-electrons from platinum and silver," by Otto Stuhlmann, Jr., University of Pennsylvania.

"Ionization and excitation of radiation by electron impact in nitrogen," by Bergen Davis and F. S. Goucher, Columbia University.

"Energy in continuous X-ray spectra," by C. T. Ulrey, Columbia University.

"An experimental investigation of the characteristic X-ray emission from molybdenum and palladium,” by Benjamin A. Wooten, Columbia University.

"Characteristic X-ray emission as a function of the applied voltage," by Bergen Davis, Columbia University.

"A standard of sound" (demonstration), by Chas. T. Knipp, University of Illinois.

"The air damped vibrating system: theoretical calibration of the condenser transmitter," by I. B. Crandall, American Telegraph and Telephone Company and The Western Electric Company.

"A photographic method of measuring the velocity of sound waves near the source of sound,'' by Arthur L. Foley, Indiana University.

"The effect of intensity and distance on the velocity of sound," by Arthur L. Foley, Indiana University.

"The influence of the pressure and time em. ployed in condensing a dental amalgam upon its crushing strength, at temperatures between 10° and 100° C.," by Arthur W. Gray and Paris T. Carlisle, The L. D. Caulk Company.

"Absorption in paraffined paper condensers," by L. Pyle, Washington University, St. Louis.

"An interesting case of resonance in an alternating current circuit," by H. L. Dodge, The State University of Iowa.

"On electromagnetic induction and relative motion II.," by S. J. Barnett, Ohio State University. "Eddy-current and hysteresis losses in iron at high frequencies," by C. Nusbaum, Harvard University.

"Some energy transformations with oscillatory currents," by E. F. Northrup, Princeton University.

"The effects produced upon audion characteristic curves by different kinds of signals (Buzzer Electron Relay and 60-cycle A. C.)," by A. D. Cole, Ohio State University.

"Influence of a series spark on the direct current corona," by S. F. Crooker, University of Illinois. "On the effect of a magnetic field upon cathode rays," by L. T. More and Lowell M. Alexander, University of Cincinnati.

"The physical characteristics of X-ray fluorescent intensifying screens," by Millard B. Hodgson, Eastman Kodak Company.

"Barometric ripples,” by W. J. Humphreys, U. S. Weather Bureau, Washington, D. C.

"The ultra-violet and visible absorption spectra of phenolphthaleins," by W. E. Howe and K. S. Gibson, Cornell University.

"The ultra-violet and visible absorption spectra of Orcinolphthaleins," by R. C. Gibbs, H. E. Howe and E. P. T. Tyndall, Cornell University.

"The ultra-violet absorption spectra of acetone," by E. P. T. Tyndall, Cornell University.

"Thermal conductivity of metals," by Edwin H. Hall, Harvard University.

“A mercury manometer of high sensibility,” by J. E. Shrader, Westinghouse Research Laboratory, Pittsburgh. ,, by

"A simple gauge for very low pressures, J. E. Shrader, Westinghouse Research Laboratory, Pittsburgh.

"Resonance and ionizing potentials for electrons in magnesium vapor," by P. D. Foote and F. L. Mohler, Bureau of Standards.

"The spectral photoelectric sensitivity of molybdenite," by W. W. Coblentz and W. B. Long, Bureau of Standards.

The papers by Messrs. Siebel, Foley, Crooker, More, Alexander and Coblentz were read by title.

On Saturday morning, December 29, at 10 A.M. the subject of discussion was "The relationship of physics to war. Addresses were made by Lieutenant G. P. Thomson, R.F.C., and by Lieutenant Giorgio Abetti, member of the Italian Military Mission. Informal reports upon the war activities of various laboratories were made by the following representatives:

Dr. A. L. Day, director of the Geophysical Laboratory.

Dr. I. B. Crandall, Research Laboratory of the
Western Electric Company.

Dr. Frank Wenner, Bureau of Standards.
Mr. C. E. Skinner, Research Laboratory of the
Westinghouse Manufacturing Company.

Dr. W. J. Humphreys, U. S. Weather Bureau.

The Sectional Committee announced the appointment of Professor C. T. Knipp, of the University of Illinois, to fill the vacancy on the sec tional committee made by the withdrawal of G. W. Stewart.

The Section elected by ballot the following named persons:

For member of the Council: Professor Wm. Duane, of Harvard University.

For member of the Sectional Committee: Dr. H. D. Arnold, of the Research Laboratory of the Western Electric Company.

For member of the General Committee: Dr. H. S. Hower, Carnegie Institute of Technology.

G. W. STEWART, Secretary