ATMOSPHERE IN GREAT BRITAIN AND ON THE CONTINENT. 19 



during the period generally blew from inhabited parts, and when it blew from the moun- 

 tains it only did so for a short time, and with but little force, so that the accumulated 

 impurities were not swept away. It will, however, be observed that the velocity of the 

 wind, even though it blew from a polluted direction, had a considerable influence on the 

 amount of dust. On the 3rd, 6th, and 9th of May there was much dust in the air 

 in the morning, but as the day advanced the wind rose and the number of particles 

 became smaller. 



Rigi Kulm Observations. 



Turning now to the observations made in Switzerland, and comparing them with those 

 made in 1889, a marked difference in the state of the atmosphere will be noticed. During 

 the first visit the weather generally was fine, and the air had the crisp clearness which 

 gives that hard outline and crude colouring one generally associates with Swiss scenery ; 

 whereas on the present visit the air was remarkably thick and heavy, the weather dull, 

 and the mountains loomed through a thick impure atmosphere. From the conclusions 

 arrived at in Part I., one would expect that this great difference in the condition 

 of the atmosphere on the two occasions would be accompanied by a difference 

 in the amount of dust in the air, if the humidity were the same on both occasions. 

 On comparing the results given in the tables for the different years, it will be seen that 

 there was no marked difference in the humidity ; but it will also be seen that 

 the quantity of dust in the atmosphere was much greater during the visit 

 in 1890 than during the previous year. In 1889 the highest number of particles 

 observed at this station was a little over 2000 per c.c., and this number was observed on 

 only one occasion, whereas in 1890, 10,000 particles per c.c. were observed — i.e., the 

 highest observed in 1890 was five times greater than the highest of 1889 ; and if 

 we compare the condition of the air at the level of the lake, the same contrast is apparent. 

 On the previous visit the number of particles at low level ranged from 600 to 3000, 

 while during this visit they varied from 1700 to 13,000 per c.c. Speaking roughly, 

 there was about four times as much dust in the air during the visit of 1890 as there was 

 in 1889, and the air was about four times as thick. 



On my way up the Rigi on the 15th May of 1890 I stopped at Vitznau, at the 

 foot of the mountain, to test the air at the level of the lake. From the table it will be 

 seen that the number of particles was much greater than in 1889, and that the air was 

 very thick. Three tests were made at different times, giving results varying from 10,000 

 to 11,750 per c.c. This thick haze was not due to humidity, as the wet bulb was depressed 

 10°, so that the air was what we would call very dry. On arriving at the top of the 

 mountain, the air at that elevated situation was tested two hours later. It was found 

 that here also there was a large quantity of dust, the number of particles being slightly 

 over 4000 per c.c, or double the highest number observed in 1889. 



As the air on- this day was in marked contrast to anything seen on the previous visit, 

 I shall make a few extracts from my notes on the points which specially attracted my atten- 



