520 



Intelligence and Miscellaneous Articles. 



"We have for the mass, 



2e 



T ; and employing the data assumed 



above we find m = 0*2936 grm. 



If the meteor in burning produce, for a given expenditure of 

 energy, more light than does the candle, then a less mass than the 

 one found would serve to produce the light given by the meteor. 

 From what has been observed of the spectra of meteors, it is safe 

 to conclude that their light is mainly due to incandescent vapours 

 of the materials composing the meteors. It is also known that the 

 spectra of these substauces remain unchanged throughout very 

 considerable changes of temperature, and we may therefore be 

 permitted to draw conclusions from laboratory experiments upon 

 these substances in the state of vapour. 



A lump of the Emmett Co., Iowa, iron meteorite was placed 

 upon the lower carbon of an arc-lamp and vaporized by the passage 

 of the current. The light given by the meteor-vapour was found, 

 on the average, equal to that of 40 candles. The galvanometer- 

 deflexion by the meteor at a certain distance from the thermo- 

 graph was 223*2 scale-divisions. At the same distance the candle 

 gave a deflexion of 55*4 divisions. From this we see that, for a 

 given expenditure of energy, the arc of meteor- vapour gives ten 

 times the light of the candle. Dividing the value of m obtained 

 above by 10, we have m= 0*029 grm. for the mass of a meteor 

 giving the light of a star of the first magnitude, moving with nearly 

 the parabolic velocity and lasting for two seconds. — American 

 Journal of Science, May 1890. 



OBSERVATIONS ON ATMOSPHERIC ELECTRICITY IN THE TROPICS. 

 BY F. EXNER. 



In order to investigate the relations of atmospheric electricity to 

 the moisture of the air within certain limits, the author has made 

 observations of the fall of atmospheric potential in countries with 

 high relative moisture, particularly in the Indian Ocean between 

 Aden and Bombay, in Bombay itself, and in Ceylon both on the 

 coast and in the interior. The measurements were made with the 

 well-known transportable apparatus invented by the author. The 

 present paper contains only the total material of observation in 

 tables, which comprise the date and hour of the observation, the 

 temperature, absolute and relative moisture, the fall of potential, 

 and meteorological observations. The discussion of the conclusions 

 to be drawn from these numbers is reserved for a second paper. 

 It need only be mentioned that all the values of the fall of potential 

 were positive. Near the coast the finely-divided spray arising 

 from the breaking of the waves exerted an increased action on the 

 fall of potential. On the other hand, measurements made in the 

 course of this journey in Cairo and the vicinity showed that there 

 the dust of the air exerted a lessening influence on the fall of 

 potential, which with a strong wind was so marked that the sign 

 of the fall of potential became negative. — Wiener Bericlite, xcviii. 

 p. 1004 (1889) ; Beiblatter der PhysiJc, xiv. p. 144. 



