288 



SCIENCE. 



serveas an index during the course of his experiment — one 

 violin being fixed and the other moving in a grooved slid- 

 ing rest. The second string was then vibrated in a uni- 

 torm manner, which produced an oscillatory motion, 

 which was heard on the corresponding string of the other 

 violin. The paper on the string showed the vibration at 

 a distance, and the violins were separated from each 

 other until the agitation of the paper ceased. This point 

 was marked as the limit of the vibrations and marked 

 ioo, the intermediate portion being marked off to repre- 

 sent the one thousandth part of the distance. 



Experiments made at noon with this instrument, and 

 often repeated, indicited the same distance within a few 

 thousandths. The whole extent of the scale was 

 seven feet, and this distance was the limit of the greatest 

 propagation of sound under the influence of light in the 

 apparatus. Parolette further states that experiments in 

 darkness gave, as a result, a mean temperature of 0.98, 

 and that the mean difference of this propogation at noon 

 and midnight was two degrees on the scale. In conclu- 

 sion, Parolette tries to explain the results arrived at by 

 stating that durng the clay, the atmosphere is more nearly 

 saturated with oxygen than in the night, but he says it re- 

 mains to be proved that this excess is sufficient to cause, 

 such a difference in the propagation of sound during the 

 two periods and adds, " rather, may not light be the true 

 cause of this increased propaga'ion in oxygen and nitrous 

 gas ; as it is known that the former has a great capacity 

 for light, and the latter cannot be formed without its 

 presence." As the velocity of light is 900,000 times 

 greater than that of sound, it does net appear unreasona- 

 ble to explain, in this way, its effects on the vibrations 

 which proceed from sonorous bodies. J. M. 



THE NATIONAL ACADEMY OF SCIENCES. 



As the meeting held on the 16th of November last, and 

 those of the three following days, were devoted to the 

 reading of scientific papers only, little executive business 

 was transacted and no new members were elected. 



At the meeting of the Council the following deaths of 

 members were announced : 



J. Homer Lane, of Washington, in May. S. S. Halde- 

 man, of Chickies, Pa., in September, and Count L. S. 

 Portales, of Cambridge, Mass., in October. 



The decease of Professor Benjamin Peirce, of Harvard 

 College, one ot the original active members of the 

 Academy.but whose connection with it had been severed. 

 was also announced. 



Resolutions, thanking the Trustees of Columbia College 

 for providing rooms for the meeting, and to President 

 Barnard and officers of the college and other members of 

 the Academy in New York for liberal entertainment of its 

 members, were adopted. 



THE FOLLOWING PAPERS WERE PRESENTED: 



1. On the Basin of the Gulf of M-x.co.— J. E. Hilgard. 



2. On the Origin of the Coral Reefs of the Yuc dan 

 and Florida Hanks. — Alexander Agassi/. 



3. Observations on Ice and Icebergs in the Polar 

 Regions. — F. Schwatka. 



4. On the Duration of the Arctic Winter. -F. Schwatka. 



5. Mineralogical Notes. —Benjamin Silliman. 



6. The Relationship ol the Carboniferous Euphoberia 

 to living and extinct Myriapods. — Samuel II. Scudder. 



7. Report on the Dredging Cruise of the U. S. Steamer 

 Blake, Commander Bartlett, during the Summer of 

 1880. — Alexander Agassi/. 



8. On Some Recetll Experiments in Determining the 

 Electro Motive Force ol the Brush Dynamo-electric 

 Lamps operating by Incandescence.- Henry Morton. 



9. On tin- Intimate Structure of certain Mineral Veins. 

 — Benjamin Silliman. 



10. On the Ellipticitj of the Earth as Deduced from 

 Pendulum Expi rim< ni . < '. S, Peii 



11. On an Improvement in the Sprengel Air Pump. — 

 O. N. Rood. 



12. On the Thermal Balance. — S. P. Langley. 



13. On the Measurment ot Radiant Energy. — S. P. 

 Langley. 



14. Causes which Determine the Progressive Move- 

 ments of Storms. — Elias Loomis. 



15. On the Autimony Mines of Southern Utah. — J. S. 

 Newberry. 



16. On the Conglomerate Ore Deposits of the United 

 States and Mexico. — J. S. Newberry. 



17. On Photographing the Nebula in Orion. — Henry 

 Draper. 



)8. On Condensers for Currents of High Potential. — 

 George F. Barker. 



19. On Sigsbee's Gravitating Trap. — Alexander 

 Agassiz. 



20. On the Deposits of Crystalline Iron Ores of Utah. 

 — J. S. Newberry. 



21. On the Origin of Anthracite. — T. Sterry Hunt. 



22. On the Star-List of Abul Hassan. — C. H. F. Peters. 



23. Dimensions of the Brain and Spinal Cord in some 

 extinct Reptiles.- O. C. Marsh. 



24. On the Rimravidce. -E. D. Cope. 



25. On the Miocene Canidae. — E D. Cope. 



26. On a New General Method in Analysis. — Wolcott 

 Gibbs. 



27. Note on the Relations of the Oneonta and Mon- 

 trose Sandstones with the Sandstones of the Catskill 

 Mountains. — James Hall. 



ON THE MEASUREMENT OF RADIANT 

 ENERGY.* 



By Prof. S. P. Langley. 



SirWdliam Herschel showed that a thermometer indi- 

 cated more heat beyond the darkest red of the spectrum 

 of a prism than in the brightest part of the color ; there- 

 fore, he concluded that light and heat were essentially 

 different things. Thrs view has apparently been con- 

 firmed by numerous other European experiments, and 

 has been set forth in all but the most recrtit text-books, 

 where different curves are drawn to exhibit the light and 

 the heat of the sun. Of late years many leading minds 

 have recognized that these were only different manifesta- 

 tions of radiant energy. Prominent ameng these is Dr. 

 John W. Draper, who asserted this principle long ago, 

 and who has always maintained that if the heat in a 

 pure diffraction spectrum could be accurately measured, 

 its distribution would be found almost identical with 

 that of light. This was an experiment, which, however, 

 could never have been satisfactorily performed had it not 

 been for the skill of Lewis M. Rutherfurd, Esq., of this 

 city, who has made at his private expense the exquisitely 

 delicate apparatus which can produce pure -spectra, with 

 a success far greater than any attained by the most 

 skdlful professional artisans of Europe. 



By the use of one of these "gratings," made on Mr. 

 Rutherford's engine by Chapman, and the employment 

 of the thermal balance described in another paper, 1 

 succeeded in obtaining for the first time full and exact 

 measurements of the distribution of energy in a pure 

 spectrum, where no lens or prism had been used, and of 

 fixing its relative amount, as determined accurately by 

 the wave-lengths of light in all parts of the visible spec- 

 trum and in the ultra red. It remained to make some 

 minute corrections for the selective absorbtions of the 

 reflecting apparatus employed. The essential result, 

 however, is of high theoretical interest ; it is, that heat 

 and light as received from the sun are now experiment- 

 ally proved, so far as such measurements can prove it, to 

 be in essence the same thing. The old delineations of 



\\< hI before die National Academy of Sciences, N. V-, 1880, 



