ATMOSPHERE OF GREAT BRITAIN AND ON THE CONTINENT. 629 



Rigi Kulm, 1892. 



We come now to the observations made on the Rigi Kulm in 1892, Table II. On 

 leaving Lucerne on the 18th May on my way up, the air was tested at the bow of the 

 steam-boat and found to have 5000 particles per c.c. At Vitznau the number was very 

 variable, owing to shifting winds ; at 10.30 a.m. it was 3550. On arriving at the Kulm 

 the number at 1 p.m. was 5100, and it gradually fell to 1920 per c.c. at 7 p.m. The air 

 during the afternoon was fairly dry, but there was a very thick haze, which nearly veiled 

 the lower slopes of Pilatus. 



The early morning of the 19th was cloudless, but there was a good deal of haze. This 

 haze remained all day, the wind being northerly and the number of particles high, varying 

 from 1050 to 2050 per c.c. 



The air on the 20th remained very hazy, though hardly so thick as on the previous 

 day ; the number of particles was, however, much higher, which was probably due to 

 impurities brought to the Kulm from Lucerne, the wind at the time being from that 

 direction. It will also be noticed that the air was drier on this day than on the 19th, 

 which would help to make it clearer even though there were more particles. 



The wind continued to blow on the 21st from the impure direction, and the number 

 of particles still remained high. The top of the mountain was in cloud in the morning 

 but clear in the afternoon ; but during the whole day the air was very thick. The 

 numbers were very irregular, indicating mixed conditions. The high numbers were 

 probably again partly due to the wind being from the direction of Lucerne. 



It will be noticed from Table II. that on the 21st high and low numbers were not 

 always associated with cloud and clear air. In the early morning the observations were 

 made in cloud, but the numbers were low. As the day advanced the numbers rose high 

 in dense cloud, and then became less in thin cloud, but at 10.45 a.m., after the clouds 

 had risen above the place of observation, the numbers again rose very high. This last 

 observation, however, is not at variance with those made the previous year, as the con- 

 ditions were different, the observation being made below cloud-level. It will be seen 

 when the high numbers were observed in clear air at 10.45 a.m. that this air was nearly 

 saturated, and if this impure saturated air had been carried up to cloud-level, condensa- 

 tion would most probably have taken place. In other words, the air in which the high 

 numbers were observed at 10.45 a.m. was an undeveloped cloud. 



The sky was cloudless on the morning of the 22nd and remained so all day. The 

 number of particles was high in the morning and continued high all day, and the air was 

 thickly hazed. This haze was very marked at sunset, the coloured dust-veil having 

 much the same appearance as was observed in 1890. 



The air on the morning of the 23rd was clearer than on any day duriag this visit. 

 The wind was from the south, which brought pure and very dry air. By 11 a.m. the 

 sky was overcast, and half an hour later the clouds descended on the Kulm. Though 



VOL. XXXVII. PART III. (NO. 28). 5 C 



