April 10, 1897.] 



SCIENCE. 



613 



land, are the other well-known high alti- 

 tude stations. Epoch-making balloon as- 

 cents were those of Dr. John Jeffries, of 

 Boston, who made the first scientific balloon 

 voyage from London in 1784; Gay Lussac 

 in 1804 (23,000 ft.); Coxwell and Glaisher 

 in 1862 (29,000 ft.), and Croce-Spinelli, 

 8ivel and Tissandier, in 1875, in which the 

 two former were asphyxiated. In 1894 

 Berson ascended alone to an altitude of 

 about 30,000 ft., his barometer reading 9.1 

 inches, and the minimum temperature being 

 -54° Fahr. Pilot balloons, without aero- 

 nauts, have ascended over 10 miles on two 

 occasions, the ' Cirrus ' in July, 1894, bring- 

 ing down a barograph reading of 3.3 inches, 

 and a thermograph reading of -64° Fahr. 



VISIBILITY OF MOUNTAINS AND ATMOSPHERIC 

 DUST. 



A PAPER by Schultheiss, in the Meteor ol- 

 ogische Zeitschrift for December, discusses a 

 matter of some interest that has not yet 

 been much considered. It concerns the ef- 

 fect of the dust in the atmosphere in rela- 

 tion to the greater or less visibility of dis- 

 tant mountains. Observations on the visi- 

 bility of the Alps have been made for 20 

 years past at Hochenschwand, a station in 

 the southern Black Forest, at an altitude 

 of 1,000 meters and commanding, under 

 favorable conditions, an extended view of 

 the Alps as far as Mont Blanc. Three de- 

 grees of visibility are noted, designated re- 

 spectively as 0, 1 and 2, the latter figure 

 denoting the greatest clearness of view. A 

 careful study of the records and of the 

 weather conditions prevailing at the times 

 of observation reveals the fact that the Arisi- 

 bility is best under anticyclonic conditions 

 or during the prevalence of a foehn wind. 

 In both cases there is a descending move- 

 ment of the atmosphere, and as the upper 

 strata are cleaner and purer than the lower 

 this process results in causing greater clear- 

 ness of the air and hence a higher degree of 



visibility. Ninety per cent, of all the cases 

 in which the view of the distant Alps was 

 clear are found to be associated with such 

 anticyclonic or foehn conditions. Cleaning 

 the air by means of rain seems to be the 

 controlling factor in the majority of the 

 other 10 per cent, of cases. Naturally, as 

 anticyclones are more frequent and longer- 

 lived over central Europe in winter, the 

 visibility is greater in winter and less in 

 summer. There is a common belief, here 

 as well as in Europe, that very clear days, 

 which give very good views of distant 

 mountains, are most likely to be followed 

 by rain. Schultheiss has investigated this 

 question in the case of the Alps as seen 

 from Hochenschwand, and finds that an 

 especially clear view is seldom closely fol- 

 lowed by rain. He also finds that the dust 

 in the atmosphere at 1,000 meters is very 

 fine and does not include large quantities of 

 coarser smoke particles as it does at lower 

 levels. 



THE BLUE HILL METEOROLOGICAL OBSERVA- 

 TORY. 



It is a very great satisfaction to learn 

 from the volume of Blue Hill Observations 

 for 1895 (Annals Harv. Coll. Obs'y, Vol. 

 XL., Pt. V.) that the President and Fellows 

 of Harvard College have secured from the 

 Metropolitan Park Commissioners of Boston 

 a lease of about one and a quarter acres of 

 land on the summit of the Hill. This lease 

 is for ninety-nine years, and will enable the 

 work of the Observatory to be continued 

 without any change in the present condi- 

 tions of exposure of the instruments. There 

 was some fear, when, a few years ago, the 

 Metropolitan Park Commission added the 

 Blue Hills to the Boston Park system, that 

 the future usefulness of the Observatory 

 might be seriously interfered with by the 

 possible erection of buildings in its vicinity. 

 It would have been a very serious loss to 

 science, not only in this country but in the 



