312 Intelligence and Miscellaneous Articles. 



it will be seen that the divergence obtained by this method does 

 not exceed -^j-^j. 



The rest of the paper contains the establishment of the formula, 

 and the experimental details and data. — Wiedemann's Annalen, 

 vol. xxviii. p. 613 (1886). 



ON THE CONSTANT OF THE SUN S HEAT. BY M. MAURER. 



The author compares the values for this constant, obtained pre- 

 viously by Pouillet, Hagen, Crova, Yiolle, and Langley ; those given 

 by Violle and Langley appear too great. This seems to arise from 

 the fact that Langley and Violle have found too high a value for 

 the amount of the solar radiation on the Earth's surface, while the 

 methods of other observers, to which those of E-ontgen and Exner, 

 and Desains must be added, agree very well with each other. 



Actinometric measurements have recently been made with a 

 new apparatus of E. Weber's, under remarkably good atmospheric 

 conditions. Six of them were made on the terrace of the Polytech- 

 nicum at Zurich, two on the top of the St. Grothard pass (2100 

 metres), and one on the Pizzo Centrale (3000 metres). According 

 to these, the maximum heat from the Sun at midday, which a 

 surface of a square centimetre receives in a minute under perpen- 

 dicular radiation, is : — 



In Zurich 1-10— 1'32 thermal unit. 



On the St. Gothard .. . 1-38— 1-41 „ 



„ Pizzo Centrale. . 1*52 „ „ 



These agree very well with the above observations, excepting for 

 Violle's and Langley 's. — Zeitschrift der Oesterr. Gesellschaft. fur 

 Meteor vlogie, vol. xx. p. 296, 1885 ; Beibldtter der Physik, vol. x. 

 p. 182. 



ON THE INCREASE OF TEMPERATURE PRODUCED BY A 

 WATERFALL. BY M. KELLER. 



The slight increase of temperature in a waterfall is powerfully 

 affected by the sources of error which the author discusses. His 

 observations at the waterfall at Terni should have given a differ- 

 ence of temperature of o, 37 ; the measured ones varied between 

 0°-08 and 0°*73. The author considers these numbers an evidence 

 of the transformation of vis viva into heat in this waterfall. — Atti 

 delta R Ace. dei Lincei [4] i. pp. 671-676 (1885) ; Beibl'dtter der 

 Physih, vol. x. p. 333. 



