March, I927. j CURRENT ToPics . 48 7

solution. The shrinking toward the centre of the mass of the sun or the impinging of meteorites on its surface are inadequate explana- tions of the duration of its heat. Since the coming of the Theory of Relativity we have become familiar with the equivalence of mass and energy and herein lies the solution of the question. " Through- out a star's interior, electrons and protons (hydrogen nuclei) nmst at intervals fall into one another and nmtually destroy one another, the energy of their fall being set free as radiation. The energy of this fall is enormous. In no other way can a given mass of matter be made to yield energy of amount comparable w~th this ; for example, whereas the ordinary combustion of a ton of coal provides energy enough to drive an express locomotive for an hour, the annihilation of a ton of coal would provide enough energy for all the heating, lighting, power and transport in Great Britain for a century." The duratio,1 of the sun's energy output is understood m part when it is known that only about one in every Io ~7 atoms of the sun almihilates itself in an hour. An additional argument for the existence in the stars ot elements of great atomic weight lies in our inability to account adequately for trie age-long emissmn of energy by elements that have atomic weights less titan that of uranium.

Professor Jeans pictures matter in its earliest state as made up of elements ot different ~atomic weight. Those with the highest atomic weight disappear first by annihilating themselves with the emission of energy. Those radio-active elements that we know on the earth are the remains of a much larger group, most of whose members are as extinct as the dodo or the carrier pigeon, i t seems that we should seek in the nebulae the elements of greatest atomic weight. When a proton and an electron annihilate each other the radiation produced has a wave-length of 1.3 -~ cm. i f this starts in the centre of a star, it impinges on a multitude of particles before it gets to the surface. At each impact its wave-length is increased by the Compton effect, so that it has become ordinary radiation by the time it leaves the star. In a nebulae, however, the number of impacts is so small, owing to the low density, that the radiation will escape with little change in its wave-length and may well be that detected on the earth by Kohlhoerster and Millikan. Confirmation of this view is found in the fact that the radiation seems to come largely from the region of the Milky \Vay. G . F . S .

Chemiker Zei tung Semi-centennial . - -Centennials , semi-, uni-, sesqui-, di- and poly-, have beeu much in evidence of late years. Mankind seems to be working up to appreciation of the past. The Chemiker Zeitung sends out a special number to celebrate its fiftieth anniversary, containing in addition to formal papers and the usual items, congratulatory letters from promi~erlt chemists. Among

488 CURRENT TOPICS. [J. F. I.

these we note a timely one from Dr. W. A. Noyes, who calls attention to the fact that no nation or group of peoples can claim to be origi- nators of chemistrv as a science. This is true indeed of all progress in knowledge. T'he claim made by Wurtz that " chemistry is a French science " was without justification.

Fifty years is not a great while in the history of general science and not even in chemistry. Liebig's Annalcn is about five ),ears from its centennial. The Chemiker Zeitun 9 is, however, a little different from the general lot of chemical journals. It has a some- what "newsy " character as we Americans would say. giving infor- mation as to the general progress and details of the science and not confining itself to formal papers or formal abstracts. We wish it many years of success and service to science. H. I,.

THE FRANKLIN INSTITUTE

OFFICERS FOR 1927

President

Vice-presidents

Secretary Assistant Secretary and Librarian Treasurer Controller

JAMES BARNES GEORGE H. BENZON, Jl,~. CHARLES E. BONINE EDWARD G. BUDD I~RANCIS T. CHAMBERS G. H, CLAMER THEOBALD F, CLARK WALTON CLARE

WM. C. L. •GLIN t HENitY HOWSON

C. C. TUTWILER WALTON ~ORSTALL HOWARD M CCLENAHAN ALFRED RIGLING BENJAMIN PRANKLIN WILLIAM P, JACKSON, JR.

Board of Managers CHARLES DAY ARTHUR W. GOODSPEEI) CLARENCE A. HALL ALFRED C. HARRISON NATHAN HAYWARD GEORGE A. HOADLEY ROBERT W. LESLEY MARSHALL S. MORGAN

CHARLES I)ENROSE JAMES S. ROGERS EORGE D. ROSENGARTEN

E. H. BANBORN HASELTINE ~MITH SAMUEL T. WAGNER J. T. WALLIS WILLIAM C. WETHERILL

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