ATMDSI'lllOlilC mST 



41 



ill Illinois. The \vhisk« wei-e taken down once a day and 

 washed in water which was allowed to stand until the 

 dust had settled. This was then removed, dried, and 

 ignited. One series of sneli samples was secured during- 

 the month of March in 1895. These ware taken daily 

 and mixed into five larger samples, each of which repre- 

 sented days with maximum hourly wind velocities rang- 

 ing between certain limits as indicated in the table of 

 analyses. The range of these velocities during the month 

 was from twelve to thirty-three miles per hour, and the 

 quantities of dust taken were quite proportionate to the 

 sixth power of these velocities, ranging from one tenth of 

 a gram to fifty grams. The analyses do not indicate 

 that there was any decided increase in the size of the par- 

 ticles transported during the days having the strongest 



wind, as might have been expected 

 (Tab. XXV). The maximum in 

 each of the samples occurs iii the 

 medium dust and the samples 

 taken on the calmest days appear 

 to contain the largest proportion 

 of coarse admixtui'es. There is, 

 however, a small decrease of the 

 fine admixtures in the dust taken 

 during the most windy day, when 

 the highest hourly velocity was 

 thirty-three miles. 



In June the same year mate- 

 rial was collected in the same way 

 and at the same place, daily, for 

 one week, and a separate analysis 



Table XXV. (Coniinued) 



loe 





Maximum 



Average. 



hourly velocity, 





33 miles. 





tr. • 



tr. ' 



14.2 1 



12.2 1 



21.3 1 



18.7 1 



50.5 l| 



43.7 p 



12.4 1 



22.7 W 



1.0 [ 



2.2 



