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and Genossan, and were straightened, annealed, and graduated by M. Dandin in Paris.

At the Bureau of Standards they were very carefully calibrated, their calibre factors, ranging from 1.000047 to 1.000096, being determined to an accuracy of about one part in a million.

The tubes were cut at points giving a resistance, including the end correction, of approximately one ohm, the cuts being located at points for which the cross-section could be most accurately calculated. The ends were ground and plane polished. The tubes were tapered at the ends to fit into the end bulbs, used in making electrical measurements, and the glass cleaning and drying fittings.

The Reichsanstalt method was employed for the determination of Mo, the mass of mercury required to just fill a tube at 0° C. A tube was exhausted, filled with mercury and placed vertically within a double-walled ice-bath, the lower end of the tube being sealed by a plane polished plate and the upper end, carrying a slight excess of mercury, being protected by a ground glass cap.

The excess of mercury was removed by stroking off with a plane polished glass plate in a gimbal mounting, the condensation of moisture being eliminated by a current of cooled and dried air directed at the end of the tube and at the stroking-off plate. Weighings were made in a special balance room, on a Stückrath balance sensitive to a hundredth of a milligramme. Six fillings of each tube were made, the mean of the average deviations of the individual fillings from their respective means being but ± 4 parts per million.

The problem of determining Lo, the length of the axis of a tube at o° C., was reduced, through the use of suitably-ruled end pieces of platinum-iridium, from one of comparing end standards to that of comparing line standards. Comparisons were made directly with corresponding known intervals on a nickelsteel meter. The length constant added, due to the end pieces, was determined by abutting the end clips and measuring the interval between the lines on them by comparison with a subdivided decimetre standard. The probable error in the lengths as determined, all things considered, did not exceed five tenthousandths of a millimetre.

Electrical comparisons of the mercury units were made by the Thomson bridge method, the mercury units and five sealed

manganin standards being substituted in turn in the same bridge

arm.

The ratio coils and the manganin standards were contained in a thermostatically controlled oil-bath, while the mercury units were in the ice-bath adjoining. Connections from the tubes to the bridge were made by inserting heavy copper conductors in the glass terminal protecting tubes of the end bulbs employed, the tubes being partly filled with mercury.

Seven fillings of each tube for electrical comparison were made in 1911. The international ohm as defined by the four mercury standards was found to be 25.5 millionth smaller than the international ohm as represented by the manganin coils at that time. The average deviation of the four tubes from their mean was but 5 parts per million.

A second and third series of electrical comparisons, made in June and December, 1912, showed the mercury standards to have changed with respect to the wire standards. Redeterminations of Mo, L., and the calculated R, were therefore made for each tube, the average change found being 1.1, 9.4, and 8.2 parts per million respectively.

On the basis of the above new determinations the international ohm, as represented by the four mercury standards in December, 1912, was 12.5 millionths smaller than the international ohm as represented by the manganin coils at the same time.

England, Germany, Japan, Russia, France, and the United States now have mercury standards of resistance. Comparison of the units defined by the mercury standards of the above countries in 1913 (those of France excepted, dates not being available) indicate a very satisfactory agreement, the average deviation of the units of the several countries from the mean being about ± 7 parts per million.

THE FRANKLIN INSTITUTE

AWARD OF THE FRANKLIN MEDAL.

At a stated meeting of the Institute, held on the evening of Wednesday, May 19, 1915, Dr. Walton Clark, President of the Institute, presiding, the Institute's Franklin Medal was awarded to:

HEIKE KAMERLINGH ONNES, of Leiden, Holland, in recognition of his "long-continued and indefatigable labors in low-temperature research, which have enriched physical science not only with a great number of new methods and ingenious devices, but also with achievements and discoveries of the first magnitude."

THOMAS ALVA EDISON, of Orange, N. J., in recognition of the value of "numerous basic inventions and discoveries forming the foundation of world-wide industries, signally contributing to the well-being, comfort, and pleasure of the human race."

The work of Professor Onnes and Mr. Edison was described by Dr. Harry F. Keller, and Dr. George A. Hoadley followed by a statement relating to the founding of the Franklin Medal.

At the conclusion of the regular business of the meeting the president of the Institute, Dr. Walton Clark, said:

The Chair now recognizes Dr. Keller to introduce the medallists upon whom, on the recommendation of the Committee on Science and the Arts, have been conferred the Franklin Medal, generously founded by Mr. Samuel Insull and nobly designed by Dr. R. Tait McKenzie.

DR. KELLER: Mr. President, our gathering here to-night in this venerable hall is an occasion of peculiar gratification and of rejoicing to the members of The Franklin Institute. It is not the recurrence of a time-honored custom, but an event which is to initiate a new series of annual functions of this Institute, made possible by the munificence of one of its distinguished members.

Your presentation, Mr. President, of the two first impressions of the Franklin Medal marks the inauguration of what we hope will every year stand out as a red-letter day in our calendar, the crowning of supreme achievement in science by the award of a medal of such artistic merit and intrinsic value as to render it a fitting tribute to the recipient.

The donor of the fund which enables The Franklin Institute to confer such an award upon scientific discoverers and inventors is Mr. Samuel Insull. He is the president of a corporation which owes its inception and its marvellous success in a large measure to scientific labor and inventive genius, to discoveries and their practical applications which have been made, not by one man, or a few men of our country, only, but by a host of workers whose lives and activities had their scene in every part of the civilized world. With these facts in mind, Mr. Insull has wisely and fittingly defined as the scope of

the new award the recognition of highest achievements in the fields of pure and applied science, without regard to the nationality of the scientist.

As in the case of the other awards made by the Institute, the naming of the Franklin Medallists has been entrusted to the Committee on Science and the Arts, and, in accordance with its custom, this committee has delegated that responsible and pleasant duty to a sub-committee of which I have had the honor to be chairman.

Impressed with the importance of recommending for the initial awards names that might stand as precedents for the coming years, the sub-committee decided upon a course which, it is hoped, will meet with the approbation of both the Institute and the public. In order to emphasize the broad scope as well as the international character of the award, it was agreed that of the two names chosen one should be that of a scientific investigator and the other a representative of applied science; also that one of the medallists should be an American and the other a foreigner. In view of conditions resulting from the war which is raging in Europe, it was deemed advisable that, other things being equal, the foreign medallist should be a citizen of a neutral country.

The two names which were the unanimous choice of the sub-committee, and which had also the unanimous approval of the Committee on Science and the Arts, meet these conditions in every respect. It may be doubted whether the selection would have been different even if it had been made without any restrictions.

The question as to which of the two awards should go to the American and which to the foreigner did not seem difficult to decide, for, while it is true that our country is now contributing its full share, and even more than that, to the advancement of science, it is universally conceded that in the practical application of scientific principles the American people are preeminent. If our country can claim to be "the land of unlimited possibilities," this phrase may certainly be applied also to the inventive power and the engineering skill of her sons. It was natural, therefore, to think of an American in connection with the award in applied science.

The scientist we desire to honor for the truly wonderful achievements he has made in experimental physics is a native of Holland, and professor in the University of Leiden. Heike Kamerlingh Onnes was little known, even among men of science, until a few years ago, when he announced the liquefaction of helium at a temperature but a few degrees above absolute zero. The award of the Nobel Prize for Physics in 1913 first directed popular attention and curiosity to the work of this scientist, and to that unique workshop of his in the Leiden University, the cryogenic laboratory. Attention was then called to the fact that the production of extreme low temperatures and the liquefaction of helium by Professor Onnes were by no means the fruits of what might be called tour de force, but the culmination of long-continued, comprehensive researches, involving profound knowledge, inventive power, experimental skill, and ability of a high order to organize and direct. This work in molecular thermodynamics derived its inspiration from van der Waals's epoch-making investigations on the critical states, and practically began in the year 1882, when the two most distinguished physicists which Holland has

produced, H. A. Lorentz and H. Kamerlingh Onnes, were appointed to the chairs in physics in the University of Leiden.

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The coöperation of the two men soon made Leiden a centre of physical research. As is well known, the achievements of Lorentz lie mainly in theoretical and mathematical physics, but Onnes at first directed his attention to the equipment and development of the laboratory. "Door meten tot weten ("knowledge rests upon measurements") he inscribed above its entrance. His great ambition was the creation of a laboratory devoted to low-temperature research. To attain this object he abandoned for many years the researches on which he had been engaged, and devoted his time to the construction of apparatus for the liquefaction of gases and the measurement of low temperatures. As a part of his plan he attached to the laboratory a training school for instrument makers, in which instruction was also given in the handling of apparatus. It was thus that he secured the staff of trained assistants which he required for his experimental work.

During the ten years he spent on constructing the cryogenic laboratory he also directed numerous important researches on electro-optical and magnetooptical subjects. In this work he enjoyed the constant coöperation of Professor Lorentz, who doubtless suggested many of the problems. Among the results was the great discovery known as the Zeeman effect.

After the completion of the liquid-oxygen equipment of his laboratory, Onnes decided to devote his entire time and attention to low-temperature research. Since 1900 the Leiden Communications, the official publication of the laboratory, presents a record of the rich harvest of results and discoveries he secured in the cryogenic laboratory. He attempted the liquefaction of hydrogen, but in this and in the solidification of hydrogen Professor Dewar, of London, his great rival, stole a march on him. Onnes, however, immediately took advantage of the new range of low temperatures by extending his equipment so as to permit the investigation of phenomena to temperatures as low as -259° C. In experimenting with a mixture of hydrogen and helium he made the remarkable observation that at the temperature of liquid hydrogen helium can be so compressed that the gas actually sinks to the bottom of the liquid.

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After innumerable preliminary trials he finally succeeded, on July 10, 1908, in liquefying helium, an achievement which is one of the greatest triumphs of experimental skill and of ingenious combination of every conceivable reThe temperature at which liquefaction took place was -269°, and by allowing the liquid to boil under reduced pressure a temperature but one degree above absolute zero was reached. Time does not permit me to dwell on the great number of new and important results that have been obtained by Onnes himself, as well as by other physicists working in his laboratory, with the aid of liquid helium. In conclusion I would only mention an almost incredible, yet fully substantiated, observation of Professor Onnes; namely, the fact that at temperatures but a few degrees above absolute zero the resistance of metals such as mercury, lead, and tin falls to practically nil, so that an electric current will continue to flow almost undiminished after the magnet that has induced the current has been removed from the coil.

Mr. President, I now have the honor to present to you His Excellency,

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