KIMBALL: HAZE OF JUNE, 1912 403 



very low during the morning of the 11th, and markedly higher 

 again on the morning of the 12th. 



On the 8th and 9th, shortly before noon, the radiation received 

 diffusely from the whole sky was about 10 per cent of the vertical 

 component of direct solar radiation, while on the 10th at about 

 the same hour it was 30 per cent of this component. 



Sky polarization observations. Measurements with a Pickering 

 polarimeter of the polarization of sky light at the point of maxi- 

 mum show that the polarization decreased from 67 per cent at 

 9 a.m. of the 9th to 14 per cent just before noon of the 10th. It 

 increased to 42 per cent at 5.10 p.m., and to 64 per cent at sunset, 

 on the 10th, but was low during the morning of the 11th, and again 

 higher on the morning of the 12th. 



Measurements of the anti-solar and the solar distances of the 

 neutral points of Arago and Babinet, respectively, showed a slight 

 increase in the anti-solar distance of Arago's point of the 10th as 

 compared with the 8th, while the increase in the solar distance 

 of Babinet's point was more than two degrees. 



Conclusions. The decrease in the percentage of polarization 

 of skylight, and in the value of the atmospheric transmission 

 coefficient, a, between June 9 and 10, and also the increase in 

 the solar distance of Babinet's neutral point between June 8 and 

 10, are attributed to the increased haziness of the atmosphere on 

 the latter date. 



While increased haziness at the center or in the rear of an area 

 of high pressure is a common occurence at Mount Weather, the 

 haze of June 10 and 11 was of unusual density. The winds thru- 

 out the five-day period, June 8 to 12, were generally from some 

 point between north and west, and were light on the 10th and 

 1 1th. We must therefore attribute the increased haziness of these 

 two days to processes taking place in the atmosphere, rather than 

 to changes in the constituents of the atmosphere due to air cur- 

 rents from a direction differing from that which had prevailed. 



The most active process during this period appears to have 

 been convection, which must have carried considerable quantities 

 of dust and moisture from the surface to at least the top of the 

 cumulus cloud layer, or to about 3 kilometers above sea level. 



