B. TERRESTRIAL PHYSICS AND METEOROLOGY. 95 



telescope previously described, or tlie photometer, gives then 

 the ratio of the intensity of the two lights. Some white disks 

 with black centres placed at various distances give with pre- 

 cision the degree of transparency of the air in day-time. Tlie 

 transparency of the sky during the night can also be found 

 by the same instrument; but the results differ according as 

 the moon is or is not above the horizon. The thermo-electric 

 actinometer of Dessaine has also been modified in its appli- 

 cations by Marie Davy. The cyanometer of Arago is also 

 made use of. Bulletin Mensuel Observatoire de Mont /Souris, 

 1875,129. 



THE OBSERYATIOX OF POLAR BANDS. 



The Wbchenschrift, published for so many years by Dr. 

 Heis, of Miinster, has lately been transferred to the editorship 

 of Dr. Herman J. Klein, of Cologne, well known to lovers of 

 astronomy by his numerous popular essays. In his hands its 

 interest will not fail of beino; maintained. Two recent arti- 

 cles by him are especially worthy of notice, one on the im- 

 portance of observations of that form of clouds ordinarily 

 known as polar bands, which have acquired a new interest 

 owins: to the observations and theories of Prestel and Hil- 

 debrandsson. In another article Dr. Klein calls attention to 

 the project long since made by Dr. Falb of using the aste- 

 roids as a medium for determining the brightness of the 

 faintest fixed stars. Klein'' sWochenschri ft, 1875. 



TIME OF SETTING SELF-REGISTERIXG INSTRUMENTS. 



In the report of the meteorological section of the Leices- 

 ter Literary and Philosophical Society, w^e learn that the time 

 of settins: the self-registerinof instruments has been altered 

 from 9 A.M. to 9 P.M. This alteration has been made in 

 consequence of the recommendation of the Vienna Congress, 

 which has been adopted by the official and by all the princi- 

 pal private observatories of England. A new and more com- 

 plete graphic method has also been adopted for displaying 

 the daily readings of the meteorological instruments. By 

 this method a whole month's daily readings are now exhib- 

 ited in tabular form on a single sheet. Leicester Literary 

 and Philosophical Society'' s Report, 1875. 



