ATMOSPHERIC DUST, 



53 



Table XXXIV. Mechanical Composition of Shower Dust fallen at Rock Island, III., 



January, 1895. 



"Length of 

 diameter In 



147 



From the Ice of 



the MleaiSBlppi, 



near bank. 



148 



From the ice of 



the l\Hssl8sippi, 



near bank. 



149 



From a crack In 

 Ice of the Missis- 

 sippi, in channel. 



From the Ice of the 



Mississippi, centre 



of the channel. 



16-8 

 8-4 

 4—2 

 2-1 



J 



1 



1 _ 



-I 

 _i_ 



8" 



.J__ 



1(> 



O 

 JT 



et i"28 



_i _ 



1 2^ 



1 

 rsTs 



tv. < 



.5 



1.4 



15.2 



44.6 



54.0 



4.7 



.3 



> 



Average. 



atively large quantities of coarse Table xxxiv. (Continued). 



admixtures, evidently derived ^^.^ ~ 



from the ground close by (Nos. ^„^ ,,,„,,, 



144, 145, 147, 148, 151), and t\fl^t^X' 



the same is the ease with some 



material which had accumulated 



in a long crevice in the ice, across 



which the wind had been drifting 



after the deposit had settled (No. 



149). The dust taken near the ^ 



center of the channel of the Mis- ;i^-i^ 2 



sissippi river has less of the. 30.0 



coarse admixtures, as does also 49.0 



7 



that taken on snow (Nos. 146, 



150, 152, 153, 1.54, 155, 156). _^ 



