446 Intelligence and Miscellaneous Articles. 



ELECTRICAL OBSERVATIONS ON THE HOHER SONNBLICK. 

 BY PROFS. ELSTER AND GEITEL. 



Erom. the results of a series of experiments and of observations 

 on the Hoher Sonnblick at a height of 10,168 feet above the sea- 

 level, the authors draw the following conclusions. 



1. The intensity of the most refrangible rays of the sun's spectrum 

 as measured by its discharging action on negatively electrified sur- 

 faces of amalgamated zinc, increases with the height above level 

 ground, in such a manner that at a height of 10,168 feet it is twice 

 as great as on ordinary level ground. 



2. Notwithstanding this increase in the power of discharge of 

 light, we did not succeed in establishing with certainty any new 

 actinometrically active substances ; even perfectly pure freshly 

 fallen snow as well as dry rock taken from the ridge of the Sonn- 

 blick were not appreciably discharged by light. 



3. Waterfalls can produce negative falls of potential in a valley, 

 and even to considerable heights, 1600 feet. 



It may be presumed that this remarkable phenomenon is not 

 produced by friction, but by the influence of the normal positive 

 fall of potential on the finer pulverulent water which detaches itself 

 from the large masses of water. And it may perhaps be assumed 

 that, as in a rain-cloud, the process of self-induction increases to 

 high values the originally feeble negative charges of a layer of air- 

 dust at the foot of the fall. 



4. In July of this year (1890), on three days which were almost 

 cloudless until 1 p.m., the normal positive fall of potential on the 

 top of the Sonnblick was appreciably constant. The morning 

 maximum, which in the plain and in Alpine valleys occurs with 

 great regularity between 7 a.m. and 9 a.m., was not observed at a 

 height of 10,168 feet. 



5. Before the outburst of the storms which we observed on the 

 16th, 18th, and 20th July, the positive fall of potential, within the 

 cloud which sent only a small quantity of rain, sunk slowly down to 

 the value zero, at which it then remained for a long time, perhaps 

 two to three hours, until the electrical process in the cloud 

 definitely came to an end. 



6. In storm-clouds the atmospheric electricity usually changes 

 its sign after a discharge of lightuing, as with storms in the plain. 



7. St. Elmo's fire was found to constantly accompany storms ; 

 it was not found that negative St. Elmo's fire was more infrequent 

 than positive. 



8. The observation that negative St. Elmo's fire follows bluish 

 lightning, and positive, reddish lightning, was frequently confirmed 

 by us. The direction then of the electrical current which traverses 

 the atmosphere in the form of lightning appears to have an in- 

 fluence on the colour of lightning. — Wiener Bei-icJite, Nov. 1890. 



