construction of new buildings, for repairs to old buildings, and for the installing of scientific equipment. The minister of public instruction also requests 900,000 francs to complete the construction work at the Institute of Applied Chemistry; 5,243,000 francs for the extension of the work of the departments of chemistry; 800,000 francs for the enlargement of the Radium Institute, and 1,500,000 francs for the construction of a laboratory of physical chemistry.

THE organization of the new department of hygiene and preventive medicine at Cornell University has been completed, the following appointments to the staff having been made: Dr. Haven Emerson, professor of hygiene and preventive medicine, and director of the department; Dr. James Stevenson Allen, assistant professor of hygiene and preventive medicine, and assistant director of the department; Dr. Frank C. Balderry. medical adviser; Drs. J. Ralph Harris, Lawrence B. Chenowith, Richard Kimpton, Claude E. Case and John A. Herring, assistant medical advisers for men and Drs. Margaret D. Baker and Katherine Porter, assistant medical advisers for women.

DR. ELI KENNERLY MARSHALL, JR., Washington, D. C., formerly associate professor of pharmacology in Johns Hopkins University, has been appointed head of the department of pharmacology at Washington University Medical School. Other appointments A. W. L. Bray, associate in anatomy; Alfred C. Kolls, associate in pharmacology; Edgar Allen, instructor in anatomy and Edward A. Doisy, instructor in biological chemistry.

are

DR. EMIL GOETSCH, formerly resident surgeon of the Peter Bent Brigham Hospital, Roxbury, Massachusetts, has been appointed head of the surgical department of Long Island College, New York.

PROFESSOR HOWARD E. SIMPSON, associate professor of geology and physiography at the University of North Dakota, has been promoted to a professorship of geographic geology.

where n has the value of 3 or 41

If n be given the value 2, and n the successive value 3, 4 and 5, lines result at wavelength 1640.1, 1214.9 and 1084.7. My previous investigations of the helium spectrum did not afford much evidence as to the existence of these lines; a recent search, however, has been more successful. With a powerful disruptive discharge in helium, a sharp, fairly strong line appears at 1640.2; no trace of it is found in hydrogen under the same electrical condition and it does not occur in helium when the discharge circuit is free from capacity. Under the same violently disruptive condition the line at 1216, always present in helium and hydrogen, develops a satellite on its more refrangible side, this satellite is not well resolved, but its wave-length appears to be about 1215.1. The region that should be occupied by 1084.7 is obscured by a strong pair at 1085, probably due to an impurity.

Owing to the difficulties of vacuum spectroscopy it is perhaps unwise to claim that the evidence in this case is conclusive. I regard it as very probable, however, that two members of this series in helium have been found in the extreme ultra-violet.

HARVARD UNIVERSITY, October 25, 1919

THEODORE LYMAN

1 Evans, Phil. Mag., 29, p. 284, 1915. 2 Astrophys. Jour., 43, p. 92, 1916.

DOUBLE USE OF THE TERM ACCELERATION

TO THE EDITOR OF SCIENCE: Dr. Hering's letter in the issue of October 24 raises a question of scientific terminology of a kind not altogether unusual. He contends that the term "acceleration " is used in one sense by the engineer, namely, to signify the rate of change of speed; and indiscriminately, in two different senses by the physicist, one of these meanings coinciding with the engineering usage, and the other conflicting with it. This second use of the word is to denote the vector rate of change of another vector, the velocity. As I understand his letter, he proposes that the physicist abandon this second meaning in favor of the first.

Dr. Hering is an eminent engineer, and I leave it to other engineers to question, if they choose, his right to speak for them. I must protest however, against his version of the views of physicists. The term acceleration, in its strict sense, is now used by physicists only with the second of the two above meanings, and then applies, when used without any qualifying word, only to the motion of a point or particle. The word is sometimes used, in order to avoid circumlocutions, to denote merely the scalar magnitude of the vector. The need of a new word to express this second notion, in the manner in which we now customarily distinguish between velocity and speed, has long been felt. This somewhat loose usage is however quite different from the definition recommended by Dr. Hering, which would give it the meaning tangential component of the acceleration." It would be rash to assert that the term is never used in this sense by physicists, for carelessness of language is hard to avoid, but few would be found to defend the usage.

Dr. Hering chooses as an illustration of the divergents of physicist and engineer:

... the revolution of a fly-wheel at a constant speed, the rim of which to the physicist is being constantly accelerated while to the engineer there is no acceleration, as the speed is constant.

The physicist argues, and quite correctly, that a moving body represents a vector quantity, as it has both speed and direction. The same external

force applied to such a moving body will change either the speed or the direction, depending upon the relative directions of that force and of the moving body. But as force is defined as mass X acceleration, the physicist, apparently forgetting the difference between pure and applied mathematics, methodically divides this force by the mass and calls the quotient acceleration. It simplifies his mathematics.

I have quoted these remarkable sentences at length, because I should not dare to attempt any summarizing paraphrase. Assuming that the physicist is "arguing correctly" when he makes a "moving body represent a vector quantity," the offense seems to consist in apparently forgetting the difference between pure and applied mathematics." What is this difference? It is that the "pure" mathematics is applicable to dynamical problems, whereas Dr. Hering's "applied" mathematics is not.

66

The case of the revolving fly-wheel offers no real difficulty either of treatment or of terminology. The "acceleration" of the flywheel as a whole is either a term without meaning, or applies to a translatory movement. Any point or particle of the wheel is accelerated toward the axis, from which we infer the existence of a force in this direction acting on the particle. Of the fly-wheel as a whole, we speak of the "angular acceleration," which is zero when the angular speed is constant and the direction of the axis invariable. From the vanishing of this vector we infer, not the absence of an external force, but the absence of an external torque or couple.

Take the case of a falling particle, describing a parabolic trajectory, and compare the

two statements:

(a) The acceleration is g, vertically downward.

(b) The acceleration is g cos e, where ◊ is the angle between the velocity and the downward vertical.

The second of these statements is in conformity with engineering usage, if I understand Dr. Hering correctly. The first statement describes the motion in such a way that if we know the velocity at any time we can

find the velocity at any subsequent time, by adding the vector gt vertically downward to the original vector velocity. The second statement assumes, so far as I can see, a knowledge of one of the quantities we need to calculate. I should very much like to see Dr. Hering's "applied" mathematics applied to this simple problem. So far as I can see, though the first statement simplifies the mathematics, the second abolishes it.

Scientific terminology is like a sharp knife used for the dissection of a problem, and unequaled for its intended purpose. It is an odd coincidence that the very number of SCIENCE which contains Dr. Hering's letter contains also an address by Dr. Gray of Edinburgh, in which the sharpness of this particular knife, the term acceleration in its strict sense, is specially noted. Dr. Hering's proposal is as if one should say, "I find your razor good for sharpening pencils, please shave with something else."

Surely the ends, neither of science nor engineering will be furthered by any such change as Dr. Hering recommends. The question is not one of simplified mathematics, but of clearness of thought.

C. M. SPARROW

ROUSS PHYSICAL LABORATORY, UNIVERSITY OF VIRGINIA,

NOTES ON METEOROLOGY AND
CLIMATOLOGY

AEROLOGICAL WORK-WINDS

AFTER the signing of the armistice had liberated much information that had been held as confidential, it became possible to assemble a group of papers on aerological work describing the pilot balloon methods used by the Weather Bureau, Signal Corps, and Navy for observing winds at various levels, and presenting the results of various lines of research. The use of thousands of two-theodolite pilot balloon runs established an empirical formula for the ascensional rate

1 Mo. Weather Rev., April, 1919, Vol. 47, pp. 205-231. Separates of these are still available: apply to Chief, U. S. Weather Bureau, Washington, D. C.

of pilot balloons which tallied remarkably well with the formula derived from theoretical considerations. This formula is

V = 71(l/L2/3) 5/8 = 71(13/L2) .208,

in which represents velocity, the actual lifting power of the balloon ("free-lift"), i. e., the weight it will support, and L the total lift (free-lift plus weight of balloon). Surprising as it is, pilot balloons ascend at a nearly constant rate, once they are above the more or less turbulent surface layer of air. Thus, single theodolite observations of angular altitude and azimuth of a balloon once a minute, when used in conjunction with the computed ascensional rate will yield reliable information as to the actual positions of the balloon, and, therefore, of the direction and velocities of the wind at all levels from the surface to the height at which it becomes lost to view. At the Aberdeen Proving Ground, temperatures for computing the densities of the air in the several altitude zones have been obtained by daily airplane ascents to a height of 10,000 feet. The score of pilot balloon stations in the United States east of the Rockies telegraph free-air wind data to the Weather Bureau in Washington twice daily, where they are used not only for aeronautical forecasting, but also as an auxiliary in making surface weather forecasts.

Meteorological kite flights are now being made at six stations daily (except when winds are light) for recording winds, relatively humidities, and temperatures aloft. The results are telegraphed to Washington daily, and later are published in Monthly Weather Review Supplements, where they become available for detailed investigation.2

The movements of dust, smoke and clouds are useful as well as balloons and kites for determining the movements of the free air. Dustfalls which occasionally occur in the northeastern United States have been traced

2 See, for instance, V. E. Jakl, "Some observations on temperatures and winds at moderate elevations above the ground," Mo. Weather Rev., June, 1919, pp. 367-373. Separates of these are still available: apply to Chief, U. S. Weather Bureau, Washington, D. C.

back to the arid portions of the southern Great Plains.3 Observations of forest-fire smoke also give reliable information of air movements over long distances, as in October, 1918, when Minnesota smoke was observed throughout the eastern half of the United States except along the gulf and south Atlantic coasts. Observations on clouds may be complementary to those on pilot balloons, for the usefulness of pilot balloons decreases as the cloudiness increases. How cloud movements may be used in local weather forecasting has been discussed by A. H. Palmer for San Francisco, M. L. Fuller for Peoria, Ill., and H. H. Martin for Columbus, 0.5

AIRPLANES AND THE WEATHER

An article on the "Effect of winds and other weather conditions on the flight of airplanes " is a rather extensive, though by no means complete, compilation and discussion of aviators' meteorological experiences. To quote from the synopsis:

The disturbances of the air due to daytime convection are one of the prime sources of bumpiness. Especially on hot summer days do strong, rapidly rising currents of air penetrate to great altitudes and, where encountered, jolt the airplane. Where the cooler air is descending, the effect is similar to that of falling into a "hole." The height to which the effects of surface roughness extend when the wind is blowing depends upon the speed of the surface wind and the height of the obstruction.

In the free air, aviators' observations show how the layers of air flow over one another, the interface sometimes being marked by clouds and sometimes entirely invisible. At such levels are encountered billows or waves, and considerable difficulty is sometimes experienced in flying

3 See Winchell and Miller, Mo. Weather Rev., November, 1918, Vol. 46, pp. 502-506.

4 Mo. Weather Rev., November, 1918, pp. 506509.

5 Mo. Weather Rev., September, 1918, pp. 407413; July, 1919, pp. 473-474, and August, 1919, pp. 567–570. A limited supply of separates is held by each of the authors named: address, "Weather Bureau Office" at cities named.

through such regions. Clouds, rain and fog all contribute to the discomfort and danger of flying. Perhaps the most interesting are the experiences in the thunderstorms and the up-and-down winds which accompany such storms. As the driving wedge of cold air at the surface advances ahead of the storm, the air into which the storm is moving is forced upward. The maximum turbulence is found in the region of the squall cloud, but the force of the rising air ahead of the storm is sufficient to carry up an airplane considerably, in spite of the efforts of the pilots to keep the nose of the plane down. The dangers from lightning and hail, are also quite as important as those from the capricious winds.

There is an annotated bibliography at the end. This article bound with two on ballooning and with reviews of Y. Henderson's "Physiology of the aviator," and H. Luckeish's "High lights of air travel," may be had on application to the Chief, U. S. Weather Bureau.

CHARLES F. BROOKS

SPECIAL ARTICLES

A PRELIMINARY NOTE ON FOOT-ROT OF CEREALS IN THE NORTHWEST

DURING the first half of May, 1918, the Station Entomologist was called to Olympia, Wash., to consult with the farmers and county agent concerning an outbreak of aphis on wheat. He found that the aphids were not responsible for the whole trouble and submitted samples of wheat from the unthrifty fields to the station plant pathologist for diagnosis. Subsequently specimens showing the same disease were submitted from this and other localities in western Washington through the county agents of the respective counties.

Among the first lot of plants were some showing lesions at the base of the stem. These lesions were elliptical, light-centered, penetrating the leaf-sheath and the surface of the stem. Plants with these lesions and others with a general blackening of the lower nodes showed death of the roots at the first node, the plant attempting to make good this loss by putting out roots at the second node. In some

10 figs.

killed and roots had been put out at the third

node. Affected plants were sickly in growth, yellowish in color and showed little or no stooling.

Later reports, especially from Cowlitz County, showed that the disease was responsible for uneven stand in the field with considerable lodging, the stems breaking over near the surface of the ground. As reported the disease showed no relation to type of soil or system of culture. The disease also appeared on oats and barley but in less severe form and showed more of a general blackening of the base of the stem and death of roots.

The disease was reported from Cowlitz, Snohomish and Thurston counties on wheat with the greatest severity in Thurston county, while it was reported from Cowlitz county as causing most injury to maturing grain. Reports of the disease on barley were received only from Pierce county. On oats the disease occurred in Clarke, Pierce and Snohomish counties. The wheat crop in certain localities of Cowlitz and Thurston counties suffered material injury while no data are at hand to show that the disease caused any material damage to the other cereals.

In 1902 Cordley1 reported a foot-rot of cereals in Oregon but gave only a brief description of the disease and did not determine the causal organism. The disease he mentions is undoubtedly identical with the disease which appeared during 1918 in western Washington. No other occurrences of the disease in the united States are recorded. The disease is either a newcomer or has escaped general notice up to the present time.

A very careful microscopic study of the fungus found in the stem lesions was made in the attempt to determine the fungus. The mycelium was sterile, dark brown in color, with

constrictions at the origin of side branches. The mycelium agreed fairly well with Rhizoctonia solani Kuhn., except in the diameter of the hypha which were only about half as large. In case of plants showing a very pronounced blackening at the base of the

1 Cordley, A. B., Ann. Rpt.' Ore. Agr. Expt. Sta., 1912, pp. 66-67.

culm it was found that this was due to a very compact surface growth of dark brown hyphæ, approaching in some cases almost to a sclerotial formation.

No fruiting stage of the fungus has as yet been connected with the sterile stage on the base of the culms. Until this is done we can only compare symptoms, and vegetative characters of the fungus with published descriptions of foot-rot diseases of cereals. There seems to be a very close similarity between the disease as it occurs in Washington and the foot-rot of cereals caused by Ophiobolus graminis Sacc., as described by McAlpine❜ and others.

Ophiobolus graminis and other foot-rot fungi are known to produce an ascigerous stage on old stubble, so it seems probable that the fungus causing the foot-rot of cereals in western Washington will be found to have a perfect or ascigerous overwintering stage on the stubble of affected plants. There is also a possibility of the disease occurring on the native grasses. It is on these wild hosts that some of the foot-rot fungi are known to be carried through a crop rotation. It has not been possible to make a careful field study for the discovery of the ascigerous stage. In the limited work undertaken a species of Pleospora is the only perithecial form that has been found in the old wheat culms. It is not yet possible to say whether the disease in Washington is identical with any of similar European or Australian diseases.

Reports indicate that the disease is already rather widely distributed in western Washinging and Cordley's account of the disease would indicate that it may have been present for a considerable time. Time alone will determine whether the disease will become as serious as the foot-rot diseases of cereals in Europe and Australia have been.

B. F. DANA, Assistant Plant Pathologist AGRICULTURAL EXP. STATION, PULLMAN, WASH.

2 McAlpine, D., "Take-All and White Heads in Wheat," Bul. Dept. Agr. of Victoria, 9: 1-120, 1904.