896 



SCIENCE 



[N. S. Vol. XXX. No. 781 



The Application of the Electrical Resistance 



Thermometer to Pyrhelionietry : Professor C. F. 



Maevin, of the U. S. Weather Bureau. 



Absolute measurements of solar radiation by 

 the use of actinometers, or pyrheliometers, of the 

 Pouillet type, in which tlie heating and cooling of 

 a short copper cylinder, more or less filled with 

 mercury, alcohol, etc., can not be made with satis- 

 factory accuracy because of the unequal distribu- 

 tion of heat throughout the mass of the block, the 

 differences in specific heat of the component parts, 

 and the uncertainty as to the exact mass of 

 material involved in the observed temperature 

 change. 



Most of the difficulties of the problem are mini- 

 mized or eliminated by the use of the electrical 

 resistance thermometer. For this purpose a short 

 cylinder is formed, about three centimeters in 

 diameter and a half centimeter long, by winding 

 up two layers of very thin ribbon of pure nickel. 

 Layers of very thin silk insulate the coils of nickel 

 from each other, and the whole is cemented by 

 shellac. 



The nickel ribbon serves the double purpose of 

 constituting the substance which receives and ab- 

 sorbs the solar radiation to be measured, and, by 

 its large variation of electrical resistance with 

 temperature, it is itself the thermometer that 

 shows its own mean temperature. 



The new construction enables the mass and the 

 specific heat of the block to be determined directly. 



A pyrheliometer with equatorial mounting and 

 mechanism for operating the shutter by electrical 

 control was exhibited. The auxiliary apparatus 

 for the electrical measurement of temperature was 

 also explained. Plans were described for meas- 

 uring the amount of radiation which unavoidably 

 falls upon the instrument from a greater or less 

 portion of the sky within 5° or 10° from the sun. 



Tentative preliminary observations using a cop- 

 per block with a nickel-wire thermometer coil 

 imbedded therein gave results from 6 to 10 per 

 cent, lower than the Angstrom pyrheliometer. 

 Th3 specific heat of the block was not accurately 

 known. 



Seasonal and Storm Vertical Temperature Gradi- 

 ents: Dr. W. J. HuMPHEEYS, of the U. S. 



Weather Bureau. 



About one hundred and fifty sounding balloon 

 records, obtained in Europe, were grouped and 

 arranged according to season and to the height of 

 the barometer. On plotting temperature against 

 altitude it was found that during the summer the 

 atmosphere was warmer than in the winter at all 



levels from the surface of the earth to the greatest 

 altitude reached; or, that seasonal changes in 

 temperature extend to all sounded altitudes. The 

 gro\iping of the records according to the height of 

 the barometer showed that during the summer a 

 barometric high commonly is accompanied by air 

 which relative to that in a low, is warm from the 

 ground up to about ten kilometers, or to just 

 below the isothermal layer; but that in the iso- 

 thermal layer it is relatively cold. During the 

 winter the same relations hold at all levels except 

 near (within two kilometers) the surface of the 

 earth where the air is colder when the barometer 

 is high than when it is low. 



Presumably these results are not due to mere 

 pressure differences, but rather to the amount of 

 moisture in the atmosphere which is greatest 

 generally when the barometer is low. This moist 

 air, being a good conductor, will cool, under like 

 exposure, to a lower temperature than will an 

 equal amount of dry air, such as is commonly in 

 a high barometer region, and in so doing will 

 radiate more heat to and through the upper air 

 and thereby correspondingly warm it, hence the 

 cool low and warm upper atmosphere when the 

 barometer is low and the air moist, and the re- 

 verse when the barometer is high and the air dry. 

 R. L. Faeis, 

 Secretary 



THE SCIENTIFIC ASSOCIATION OF JOHNS HOPKINS 

 UNIVEESITY 



At the meeting of the association in November 

 an interesting lecture was given by Professor B. 

 E. Livingston, the newly elected professor of 

 physiological botany, under the title, " Work of 

 the Desert Laboratory." Professor Livingston 

 presented a brief historical outline of the con- 

 ception and development of the desert laboratory 

 idea, together with a description of the main 

 botanical features of the country adjacent to 

 Tucson, Ariz., and a consideration of the already 

 excellent material facilities for research at the 

 laboratory. A cursory account of some of the 

 most important problems which have been attacked 

 by the difi'erent members of the staff was given, 

 including such topics as the theory of descent and 

 heredity, the physiology of water storage in 

 plants like the cacti, the physiology of parasitism, 

 the special physiological anatomy and morphology 

 of desert species, the physical environmental fac- 

 tors, the ecology of the desert, etc. The lecture 

 was illustrated by lantern slides and photographs. 



C. K. SWABTZ, 



Secretary 



