ATMOSPHERE OF GREAT BRITAIN AND ON THE CONTINENT. 



659 



Kingairloch number being 77,525 and the Alford one 75,474. But the values of C do 

 not agree so well for wet-bulb depression of from 4° to 7°. The Kingairloch figure is 

 105,923, while the Alford one is only 95,153, or about 10 per cent. less. One reason for 

 this is, that in the Alford observations there are a great many of them made in very pure 

 air, and it will be seen from the tables for both stations that all the observations made 

 when there are few particles give a low value for C In the Alford observations for wet- 

 bulb depression of from 4° to 7°, half of the observations were made in air with less 

 than 500 particles per c.c, while in the corresponding observations at Kingairloch there 

 was only one. The reason of the low value of C in pure air is probably clue to the 

 difficulty of making estimates of haze in very pure air; and as 250 miles has been taken 



Table XVI. — Shoiving the Relation betiveen the Number of Dust Particles and the Transparency 

 of the Atmosphere at Alford when the Wet-Bulb Depression was from 4° to 7°. 



Date. 



Lowest 

 Number. 



Highest 

 Number. 



Mean 

 Number. 



Limit of 



Visibility in 



Miles. 



C. 



18th September 



1891 



94 



315 



204 



250 



51,000] 





24th 



1892 



196 



217 



206 



250 



51,500 





17th 



>) 



308 



322 



315 



250 



78,750 





13th „ 



1893 



56 



616 



331 



250 



82,750 





29th 



1892 



350 





350 



250 



87,500 





28th 





294 



469 



381 



250 



95,250 





» >> 



1891 



385 



392 



388 



250 



97,000 



Mean, 

 '95,153 



7th 



1893 



455 





455 



250 



113,750 



6th 





485 





485 



250 



121,250 



9th 



5) 



427 



737 



582 



200 



116,400 





26th „ 



1892 



530 



750 



640 



100? 



(64,000) 





5th 



1893 



975 





975 



100 



97,500 





25th „ 



1891 



1025 





1025 



100 



102,500 





5th „ 



1893 



2800 





2800 



40 



112,000 





25th 



1891 



4200 





4200 



30 



126,000 





Table XVII. — Showing the Relation between the Number of Dust Particles and the Transparency 

 of the Atmosphere at J If or d when the Wet- Bulb Depression was 7° and above. 



Date. 



Lowest 

 Number. 



Highest 

 Number. 



Mean 

 Number. 



Limit of 



Visibility in 



Miles. 



C. 



15th September 1893 

 6th „ „ 



29th „ 1891 



19th 



1892 



12th „ 1893 

 5th „ 



238 

 434 

 497 

 483 

 469 

 1025 

 1400 



273 



607 



950 



524 



1400 



255 

 434 

 552 

 716 

 496 

 1212 

 1400 



250 



250 

 250 

 250 

 250 

 100 

 100 



63,750' 

 108,500 

 138,000 

 179,000 

 124,000 

 121,200 

 140,000 



Mean, 

 a24,921 



