ATMOSPHERE OF GREAT BRITAIN AND ON THE CONTINENT. 



635 



variable. It will be seen from the tables that during the whole of the time of the 1889 

 visit the wind was southerly, that is from the Alps. During the 1890 visit it was only 

 once steady from the pure direction. It was so four times in 1891, but it was never 

 steady for any length of time from the pure direction in 1892 and 1893. Table VII. 

 shows that the wind was from the impure direction or variable on two days in 1890 

 and 1891, and that it was always from the impure direction or variable during the visits 

 in 1892 and 1893. 



At the bottom of Tables VI. and VII. are given the mean of the highest and lowest 

 number of dust particles in air for the pure and impure directions. From these it 

 will be seen that when the wind blew from the Alps the mean of all the lowest observa- 

 tions was 421 and of all the highest 1305 ; while, when the air was from polluted areas, 

 the mean of the lowest was 1092 or 2*6 times greater than the mean of the lowest in air 

 from the Alps, and the mean of the highest was 5755 or 4*4 times greater than when the 

 wind was southerly. 



Dust and Transparency on the Rigi Kulm. 



The effect of dust on the transparency of the atmosphere is brought out roughly 

 in Tables VI. and VII. It will be seen from these tables that, when the wind was 

 from the Alps and the number of particles was small, the air was always either 

 " clear "or " very clear," whereas, when the wind was from impure directions and the 



Table VII. — Shoiving the Highest and Lowest Number of Dust Particles observed on the Rigi 

 Kulm when the Wind was from Inhabited Areas. 



Date. 



Wind. 



Highest 

 Number. 



Lowest 

 Number. 



State of the 

 Air. 



15th May 1890 



N.E. 



4,200 





Thicldsh. 



17th , 













E. to N.W. 



6,100 



1,200 



Thick. 



22nd , 



, 1891 











W. to N.W. 



2,025 



300 



Raining. 



25th , 













S.E., W., N. 



3,450 



440 



In cloud. 



18th , 



, 1892 











W.N.W. 



5,100 



1,920 



Thick haze. 



19th , 













W. to N.W. 



2,050 



1,050 



;; 



20th , 













J) 



13,750 



2,500 



Thickish. 



21st , 













W. to W.N.W. 



7,650 



900 



Thick. 



22nd , 













Variable. 



7,400 



1,000 



Thickish. 



23rd , 













S., N., W. 



1,425 



579 



Raining. 



24th , 













N.W. to E. 



6,400 



750 



Medium. 



10th , 



, 1893 











N. 



8,700 



1,500 



Thick. 



11th , 













N. to N.E. 



2,750 



441 



In cloud. 



12th , 













E.S.E., E.N.E. 



5,700 



690 



Medium. 



13th , 













E.S.E., N.E. 



16,500 



2,050 



)> 



14th , 













Variable. 



3,325 



1,100 



Clear. 



15th , 













S., N. 



4,400 



925 



Thickish. 



16th , 



? )) 











S.W. to N. 



2,650 



1,225 



Medium. 



Mean 





5,755 



1,092 





