604: Winchell and Miller — 



Size 12 3 Size 



•005 mm. 



11-15 



17-8 



11-3 



•004- -008 



1-5 





•005- -010 



2201 







•008- -016 



141 



•7 



.010- -025 



56-17 



65-8 



74-1 



•016- -032 



36-2 



5-2 



•025- -050 



5-99 







•032- -125 



31-5 



42-0 



•05 - -10 



1-22 



140 



13-2 



•063- -125 



7-8 



42-0 



•10 - -25 



104 



1-5 



•8 



•125- -250 



5-5 



100 



•25 - -50 



•58 



0-2 



•3 



•25 - -50 



30 



tr 



•5 -10 



•29 



1-0 



•2 



•5 -1-0 



•2 



. • • • 



1-0 -20 



1-08 



0-0 

 100-3 



•0 

 99-9 



1-0 -20 



100-0 









99-53 



99-9 



1. Dust from snow fall at Madison, Wis., March 9, 1918. 



2. Soil, Hays, Kansas, which is subject to blowing. E. E. 

 Free. "The Movement of Soil Material by the Wind, U. S. Bur. 

 Soils, Bulletin 68, page 168, 1911. 



3. Silt loam soil ("Waukesha") from valley loess, Douglas 

 Co., Neb., A. H. Meyer, et al., U. S. Bur. Soils, 15th Kept., 

 p, 1994, 1913. 



4. Dust from dust shower, Chicago, 111., Feb., 1896. J. A. 

 Udden, The Mechanical Composition of Wind Deposits, Augus- 

 tana Libr. Pub. 1, p. 55, 1898. 



5. Volcanic dust which fell on snow in Norway after a recent 

 eruption in Iceland. J. A. Udden, I. c, p. 36. 



No explanation is offered here for the small range of 

 sizes within which snch a large part of the Madison 

 dust is included, other than the remarkable sorting power 

 of the wind; perhaps this is a sufficient explanation even 

 as compared with the shower and volcanic dust, if the 

 smaller size of the Madison dust is remembered. 



Quantity of the dust. — Several samples of the dust were 

 obtained at Madison. Professor W. H. Twenhofel col- 

 lected the yellow snow from one measured square yard 

 of surface; A. N. Winchell obtained another sample 

 amounting to 5% liters of snow water, while smaller 

 amounts were gathered by E. E. Miller and W. J. Mead. 

 The residue left after evaporating the colored snow 

 obtained from one square yard of surface weighed four 

 grams, while the sample of 5% liters of snow water 

 yielded 5-2 grams of residue which settled to the bottom, 

 as well as -15 grams of black material, which floated at 

 the surface or in the liquid. These two determinations 

 are mutually corroborative since the second sample was 

 obtained from somewhat more than one square yard of 

 surface. They indicate that the residue amounted to 4-8 



