Intelligence and Miscellaneous Articles. 287 



MEASUREMENTS OF EADIATION ON THE SONNBLICK IN 

 FEBRUAEY 1888. BY DR. J. M. PERNTER. 



The observations were made with Violle's actinometers, which 

 were modified so as to measure the radiation, and were simulta- 

 neously effected on the Sonnblick (3095 metres) and the Eauris 

 (900 metres). 



The value of the radiation S^ in Eauris, at a temperature of 

 -8° 0., was found to be 0-151 calorie ; and on the Sonnblick, with 

 a temperature of —15°, it was S2=0-201 calorie (gramme minute). 



From this the temperature of cosmical space is calculated to be 

 -111° C. 



It follows moreover from this that the entire atmosphere possesses 

 uyiit power of absorption for rays proceeding from the earth. This, 

 however, is not the case with the atmosphere on high mountains 

 such as the Sonnblick. Hence no rays pass into the cosmical 

 space from the lower levels, that is, from the greater part of the 

 earth's surface, as maintained by Langley ; but they do so pass 

 from the tops of the hills. 



As, for the future, we are able to calculate the radiation of the 

 atmosphere from an observation of radiation, and the coefficient of 

 radiation for the entire atmosphere is equal to unity, we can deter- 

 mine the mean temperature of the atmosphere from each measure- 

 ment of radiation, for o-=AT^. 



From a comparison with measurements of Maurer, in Zurich, it 

 follows that the radiation of the atmosphere only depends on its 

 temperature, and, as a further conclusion, on the temperature 

 observed on the earth's surface. 



It can moreover be easily calculated from the above that, with \ 

 complete absence of the sun, the mean temperature of the earth ' 

 would be lowered by 103°, that is would amount to —88° C. 



By the aid of the results of measurements of the radiation the 

 solar constant may, curiously enough, be calculated with at least 

 the same accuracy as from direct measurements of the solar radia- 

 tion. *It is about 3*1 calories. — Bericlite der Wiener Akademie, 

 December 1888. 



THEORY OF ISOHYDRIC SOLUTIONS. BY SV. ARRHENIUS. 



The author has applied the term isohydric to two solutions the 

 conductivities of which are not altered when they are mixed (Wied. 

 Ann. vol. xxx. p. 51, 1887). According to the author's views, 

 what is called the electrolytic dissociation (into ions) of the two 

 electrolytes is unaltered in these circumstances when they are 

 mixed. Since, according to the investigations of Van't Hoff, the 

 same conditions of equilibrium hold for dilute solutions as for 

 gases, from the principle of entropy we can establish the conditions 

 which two isohydric solutions must obey, so that on mixture their 

 condition of dissociation is not altered. These conditions lead to 



