32 



SCIENCE 



[N. S. Vol. XXXIX. No. 992 



mercury for barometer readings (760 mm. = 

 29.92 in. = 1,013,303 dynes =■ 1,013.3 milli- 

 bars). Also temperatures will be expressed in 

 absolute centigrade degrees (273° A. = 32° F.). 

 Until January 1, 1916, the old units will be 

 retained for comparison with the new. Pro- 

 fessor Alexander McAdie, director of the ob- 

 servatory will be glad to help any one wishing 

 to adopt this new pressure scale. These 

 changes were first proposed for adoption in 

 the United States by him in 1908. 



In the report for the year ending March 31, 

 1913, the Meteorological Committee of Eng- 

 land announces that the centibar or millibar 

 will be used instead of the inch as far as pos- 

 sible for all barometric measurements. Speci- 

 mens of daily and weekly weather reports are 

 given with pressures expressed in dynamic 

 pressure units instead of inches of mercury, 

 and with temperatures in absolute centigrade 

 degrees. 



RADIATION AND CLOUD GROWTH 



In the October Meteorologische Zeitschrift ^ 

 Dr. C. Braak, of Batavia, Java, ascribes to 

 radiation certain peculiar phases in the devel- 

 opment of cumulus clouds. His description of 

 the formation of these clouds on a calm day 

 may be stated as follows. When the rising 

 sun has warmed the earth sufficiently to drive 

 local air masses to the condensation level, at 

 first single, then many small cumuli appear 

 which soon cover the whole sky. Here and 

 there larger heads rise out of the rather flat 

 cloud sheet. Soon after reaching their maxi- 

 mum height they disappear. If the cumulus 

 growth continues to the cirrus level (about 10 

 kilometers altitude) the top flattens out. The 

 lower column melts away and leaves this grow- 

 ing sheet. When through energetic upward 

 movement the cumulus cloud rises to even 

 greater heights, there is no longer a maximum 

 level where the vertical movement stops; the 

 condensed moisture falls out, and in the upper 



1 See Alexander MeAdie, ' ' New Units in Aerol- 

 ogy, " Scientific American Supplement, December 

 6, 1913, p. 357. 



2 ' ' Uber den Einfluss der Strahlung auf die 

 Wolkenbildung. ' ' 



parts of the cloud the air flows toward all sides, 

 forming gigantic cirrus rays. 



Thus there seems to be a division of the 

 atmosphere into two parts as regards cloud 

 building. This has a certain analogy with the 

 division of the atmosphere into troposphere 

 and stratosphere : the former designates the 

 atmosphere to a height where decrease of tem- 

 perature with altitude ceases, and the latter, 

 the isothermal region of unknown vertical ex- 

 tent above this. According to Messrs. Gold 

 and Humphreys' this is a radiation effect of 

 the air. Below the stratosphere radiation ex- 

 ceeds absorption and convection balances the 

 loss of heat; while in the stratosphere absorp- 

 tion exceeds radiation so the temperature rises 

 over that of convective equilibrium. If one 

 considers the disappearance of the lower part 

 of the cumulus cloud to be the result of cooling 

 and the continuance and energy of the upper 

 part as the result of warming, the analogy be- 

 comes nearly complete. Observations in cumu- 

 lus clouds over Batavia within the lower few 

 kilometers show that the clouds are colder 

 than the surrounding air at the same level. 

 Radiation may thus have greater importance 

 in cloud processes than is commonly assigned 

 to it. 



EXCESSIVE PRECIPITATION 



Some recent heavy rains have brought out 

 the following records of excessive rainfall for 

 short periods. 



3 See Dr. W. J. Humphreys, Jour. Frmiklin 

 Inst., March, 1913, pp. 216-222. 

 i Probably world 'a records. 



