per hour of study than children comparable to them in brightness are able to learn.

Extensive experiments with adults learning algebra, science, foreign languages and the like in evening classes, and with adults learning shorthand and typewriting in secretarial schools, support the general conclusion that ability to learn rises until about 20. Then, perhaps after a stationary period of some years, learning ability slowly declines. The decline is very slow, however, roughly about one per cent. per year. The chief reason why adults seldom learn a new language or a new trade is not the lack of ability, but the lack of opportunity or desire.

ITEMS

KILLING off one disease through the action of another is a medical method of increasing interest. Treatment of the paralytic forms of syphilis with inoculations of malaria has had a three years' tryout at the Mayo Clinic and was pronounced the most valuable method used thus far, by Dr. Paul A. O'Leary, of Rochester, Minn., at the meeting of the American Medical Association. Many more years of observation will be necessary, however, Dr. O'Leary emphasized, before it will be justifiable to speak of the "cure of paresis." Results must now be estimated in terms of arrest or remission, he said, as shown by the ability of patients to resume their former mode of living. The malaria treatment is not without risk as the mortality of five per cent. recorded by Dr. O'Leary shows, but he believes that this rate compares favorably with that of any untreated group, observed for the same length of time. The greatest improvement was noted where the malaria was introduced early in the course of the paresis, but striking results were cited by the Rochester specialist in cases of four years' standing.

IN a statistical study of conditions since the passage of the eighteenth amendment, presented at the American Medical Association recently, Dr. Leonard G. Rowntree, of the Mayo Clinic, Rochester, Minn., stated that alcoholism has made a striking decrease since 1917. Cirrhosis of the liver, a degenerative disease, one form of which is due to alcoholism, is also decreasing in about the same proportion, the Minnesota doctor's figures showed. The contention that urban population is notoriously wet, and rural sections notably dry, is borne out by the fact that both these conditions are found to occur most frequently in cities and are about half as prevalent in the country as in the city. Deaths from too much booze in New York in 1920 were only one seventh of those in 1916 and deaths from cirrhosis fell off more than half. In the dry and rural state of Kansas the death rate for both conditions has remained about the same as before the war. It is interesting to note, said Dr. Rowntree, that the highest mortality rate for alcoholism and cirrhosis recorded in Kansas in the last fourteen years represents the low-water mark for deaths from the same cause during the same period in New York.

DR. JAMES W. GIDLEY, paleontologist of the U. S. National Museum, has returned from a partially successful search for elephant bones to complete a great mammoth

Near

skeleton being assembled for exhibition purposes. Alva, Oklahoma, he found portions of a small elephant which were of considerable scientific interest but of a different species from the composite skeleton which the museum experts are mounting. This particular variety of mammoth came from Florida and attained a huge size, twice as large as the ordinary elephant of to-day. A prehistoric relative of the armadillo, probably a hitherto unknown species about as large as a cow, was among the skeletons. The thorough exploration of Oklahoma for animals of past ages is urged by Dr. Gidley. He states the state is rich in rock formations containing evidences of the life of 500,000 years ago.

THE pine forests of the future will not perish in infancy if the recent research efforts of J. Stewart Wiant, of the New York State College of Agriculture, are put to practical use. Hitherto there has always been a heavy mortality in pine plants started from seed in forest nurseries and later set in the hope that they may become huge trees a century or so later. The tender young plants are easily killed by parasitic soil fungi. Dr. Wiant finds that soil treatment with several chemicals, especially with some recently discovered chlorophenol mercury compounds, destroys these parasites and permits the baby pines to develop until they are strong enough to be secure against these enemies.

LACE-MAKING has become a Chinese home industry of considerable importance, according to figures published in a survey of industrial and commercial conditions in China just issued by the U. S. Department of Commerce. The customs returns show lace exports amounting to over $4,000,000, and this probably does not cover the entire quantity. The Irish lace industry was introduced into Swatow as recently as 1920 and it is said that the laces produced are equal, if not superior, to those originally made in Ireland. In several cities around Shanghai, many Chinese women and girls are busy in making filet lace. The low cost of Chinese labor makes the retail price, even with the high tariff, much cheaper than the handmade laces of Europe.

THAT tin, the metal with which most metallic food containers are lined, has absolutely no effect on the human body is the finding of Drs. E. W. Schwartze and W. F. Clarke, of the U. S. Department of Agriculture. Selecting asparagus and pumpkins as two kinds of preserved food which might be expected to enter into chemical union with the tin lining of the cans in which they had been preserved for long periods, they have been unable to demonstrate the slightest unfavorable effects of the vegetables when they were fed to guinea pigs. Further, they administered tin metal in two-gram lots, more than all the tin on several large cans, to human beings over a period of five days. By the most refined analytical methods they could find no trace of tin in the blood stream, indicating that none had been absorbed by the body. It is also proposed to determine the effect on steel cans lined with enamel instead of with a tin coating.

VOL. LXV

JUNE 3, 1927

No. 1692

New York City: Grand Central Terminal. Lancaster, Pa. Garrison, N. Y. Annual Subscription, $6.00. Single Copies, 15 Cts.

SCIENCE is the official organ of the American Association for the Advancement of Science. Information regarding membership in the Association may be secured from the office of the permanent secretary, in the Smithsonian Institution Building, Washington, D. C.

Entered as second-class matter July 18, 1928, at the Post Office at Lancaster, Pa., under the Act of March 8, 1879.

CONTRIBUTIONS OF SCIENCE TO THE

LIGHTING ART1

SCIENTIFIC Work is so varied in viewpoint and objective and it is so complexly interwoven with human interpretations and technical and commonsensical applications of knowledge that it is impossible—at least in a brief paper to establish a definite boundary between science and any of its fields of usefulness, such as a branch of engineering. Even in the scientific realm itself there is now no definite boundary between what have been termed pure science and applied science-a distinction which, in the last analysis, is now largely hypothetical. Wherever the distinction exists or is useful, perhaps the distinguishing factor is the immediate objective of the individual or of the institution which is prosecuting the work. I should define pure science, in the relatively rare cases where a useful purpose is served by doing so, as work done solely for the purpose of advancing knowledge. However, I have no patience with the implication of exalted purpose, as has been openly declared by some of the past members of the aristocracy of science and is still more or less delicately implied by the few remnants of that threadbare aristocracy. The old-fashioned idea of the purification of scientific work by intending and hoping and praying that it would never be put to the vulgar use of benefiting the multitude has almost completely atrophied-from lack of any use for it. Now scientific workers are rare whose viewpoint-if not their objective-is not the eventual usefulness of knowledge. Unless blinded by tradition one sees on every hand the benefits of applications of scientific knowledge. This commendable change in viewpoint and objective has also contributed toward the obliteration of the boundary line already referred to.

With gracious thanks for the knowledge inherited from pure science, the scientific worker, with increased happiness of mankind for his objective, may proudly stand alongside the so-called pure scientist. The latter follows his curiosity, overcoming obstacles or diverting his course as he wishes. The former with a definite objective before him requires not only the mental equipment of the former, but he must also be an interpreter of this knowledge into every-day usefulness and he must surmount the obstacles encoun

1 Abstract of an address before Section M, American Association for the Advancement of Science, Philadelphia, December 29, 1926.

tered if he is to reach the definite objective which he has chosen. And as he follows this course he does a great deal of scientific work and contributes much to the fund of knowledge. The so-called purely scientific worker increases knowledge, but it is the practical-minded interpreter who advances progress. Both are needed but, if the one is inclined to imply exalted purpose, the other may be assured that increasing human happiness, by utilizing knowledge which unused is of no value, is the most exalted purpose in human affairs.

Perhaps the foregoing may aid in demonstrating the impossibility of hewing close to the line suggested by the title of this paper and at the same time may aid in appraising the scientific contributions to the lighting art. Now let us look at the lighting art. Here again a complex web of scientific aspects confronts us. We not only have the interwoven physical sciences to consider in the production of radiant energy which is utilized in vision, but as soon as this energy produces the sensation of light we find ourselves in the extremely complex psycho-physiological realm-much of which is quite unexplored. At best in this brief paper only a few illustrative glimpses may be presented.

As in other fields of application of knowledge, we might close the discussion at this point by stating that all the accumulated knowledge since man began to think is drawn upon in some way or other in the development of the lighting art. But it would be futile to attempt to go back beyond the beginning of modern science-a few centuries ago. The possibilities of lighting increase in proportion to the safety, the convenience, the efficiency and particularly the controllability of light from adequate light-sources. Comparing the tungsten filament lamp, for example, with other light-sources in respect to the foregoing characteristics, we find that it justly deserves its overwhelming favor at the present time. A new light-source of greater luminous efficiency would also have to compete successfully with the safety and convenience of the tungsten lamp. On the other hand, no more convenient light-source has ever been produced than the candle-a portable lighting plant-but it has succumbed to greater safety, adequacy, efficiency and controllability of other light-sources. Of course, even now it has special applications where its extreme portability makes it supreme. Thus there are practical aspects which may outweigh scientific ones and vice versa.

In treating this subject one is confronted with great scientific principles and epochal discoveries and also with numberless details. In the first class let us begin with Newton's explanation of the spectrum of light in 1666. Who can appraise the influence of

this scientific contribution? The spectral distribution of energy is the very foundation-stone of lighting. It is important in the production, the measurement and the utilization of light. Then there are the laws of radiation-of Wein, Planck, Stefan-Boltzmann and others-established during the past fifty years. These have been and are used daily in studying the spectral distribution of energy from light-sources and are intimately involved in the searching investigations of emissivity, selectivity and temperature of radiators and, consequently, of the luminous efficiency of lightsources. The electron theory likewise is found at every turn, particularly in vapor and gas conductors such as arcs and so-called vacuum tubes. Metallurgical science is drawn upon heavily in the development and improvement of filament materials. But let us be content with this glimpse for the present lest we become hopelessly involved and discouraged with the magnitude of the task of giving science its due.

Let us turn to some details of gas-lighting. William Murdock about 1790 is usually credited with the first production and use of coal gas for lighting. He heated coal in closed iron containers and burned this gas in his home as it emerged from small iron pipes. However, in searching the literature we find that Clayton distilled coal in a retort at least a century before and noted that the gas emitted was inflammable. This well illustrates how unlikely the original scientific contributor of the more distant past is to receive credit, even though one were genius enough to unravel the complex web of knowledge with its threads leading into many highways and byways of science in any specific development. However, in the modern sense no outstanding achievements appear in flame light-sources until Bunsen mixed air with coal gas. The Bunsen burner revolutionized gas lighting as well as heating.

Gurney in 1826 had found that a cylinder of lime became very brilliant when heated with an oxy-hydrogen flame. Drummond immediately applied the idea to obtain powerful light-sources which he wanted in his work of surveying Ireland. The lime-light was used so widely for fifty years-particularly on the stage that language has been enriched with the phrase, "in the limelight." Much scientific work was done along this line which eventually led to the development of the gas-mantle. Talbot in 1835 found that finely powdered lime became brilliant in the flame of a spirit lamp. He also soaked blotting paper in a solution of lime salt and incinerated it. The ash glowed brilliantly when heated. Gillard in 1848 made a mantle of fine platinum gauze which lasted only a few days. The idea was revived from time to time and it received quite an impetus after the Bunsen burner was applied to gas lighting. Welsbach was

conducting spectroscopic researches on rare earths in Bunsen's laboratory. After soaking cotton in solutions of these metallic salts and burning it, he found a replica of the original fibers remained, consisting of the oxide of the metal. This ash glowed brilliantly in a Bunsen flame. He then evolved the idea of using cotton fabric and patented the commercial mantle in 1885. This was timely for gas-lighting, because it prolonged its period of formidable competition with electric lighting for about twenty-five years.

Practicable electric light sources had already appeared-the carbon arc in 1877 and the carbon-filament lamp in 1879. They would have appeared much sooner but they had to await the arrival of practicable sources of electrical energy. Going back we find Davy the first formidable investigator of the carbon arc. He also heated wires to incandescence by passing an electric current through them. But his investigations would not have been made if Volta had not supplied the Volta pile-a source of electric energy. In 1801 Davy noted that the carbon terminals of a voltaic cell produced an electric arc when touched together and separated. In 1808 the Royal Institution supplied him with a voltaic battery of 2,000 cells the first notable subsidization of scientific research. He exhibited and studied the electric are on a large scale. Faraday, his assistant and pupil, was then developing a scientific foundation which in his later studies of induction was to lay the cornerstone of the great electrical development of the future.

Thus the germ of the enormous electrical industry came into being, but the actual birth of this industry must be credited to electric lighting. Forty-four years ago Edison sent all the electric filament lamps in existence in this country to the famous Pearl Street Station in New York in a market basket. In 1925 nearly a half billion electric filament lamps were manufactured in the United States. In that year in this country the total investment in electric light and power companies was nearly eight billion dollars; sixty billion kilowatt-hours of electrical energy were generated and sold for one and one half billion dollars. Of this gross revenue two thirds came from electric lighting. Add to this the investment in the manufacture of electrical apparatus and supplies and in electrical equipment and wiring and we see business, the tax-assessor, the individual and others deeply indebted to science through electric lighting.

There were many workers on electric light sources before they actually came into use and, of course, this knowledge was available to those whose names are commonly coupled with the first really practicable ones. Brush, with the arc lamp, and Edison, with

the carbon filament lamp, are the most familiar in this country. Edison discovered that a current passed between the terminals of the filament through the near-vacuum. This is an example of the by-product of fundamental knowledge contributed by the inventor. This "Edison effect" has found many applications, for example, in the radio-tube.

Chemistry, spectroscopy and other branches of physical science contributed much to the development of a number of arcs. Jandus and also Marks enclosed the arc, greatly reducing the rate of consumption of carbon. At the present time, the arc has been largely relegated to special uses, although the magnetite arc, particularly, is still used to some extent in street lighting.

The carbon-filament lamp was steadily improved, but the first radical improvement was made by Whitney in 1906. The filament was treated by heating in an atmosphere of hydrocarbons, and it was so altered that it could be operated at a higher temperature with a satisfactory life. Higher temperature, in the case of filament lamps, means greater luminous efficiency. Therefore, efficiency. Therefore, refractoriness-high melting point-is desired. Inasmuch as carbon has a higher melting point than any of the metals now in use for filaments, one may look to it as still a possibility. The evaporation of carbon has been a limiting feature and Whitney's improvement achieved a reduction in this.

Since Mendeleeff in 1870 enunciated the periodic law of elements, scientists in the field of light-production have studied the gaps in the periodic table with much interest. One by one these gaps have been filled until the two remaining have little interest for them. They must turn more hopefully to metallurgy and to the chemistry of compounds and perhaps look toward the day when the secret of atomic structure may make it possible to make elements or compounds of the desired characteristics. This applies particularly to the production of light from incandescent solids.

In this hurried review we may pause for only a word of praise for the ingenuity exhibited by Nernst in devising the lamp which bore his name. More efficient than the carbon filament lamp which was in the field when it appeared, its cost and complex character militated against a general use of it. Tantalum and osmium were used for filaments; however, they were soon crowded out by tungsten, but experience with them was a valuable heritage. Scheele and Bergman discovered tungsten in 1781 in scheelite. It was not used for filament material until 1906-125 years later. Then it could not be drawn into wire, so the filament was made by mixing powdered tungsten with organic matter and heating this to remove