WIND DEPOSITS 685 



following an eruption on Iceland, was obtained from the United States 

 National Museum. This dust was carried a distance of 800 miles by the 

 wind. 



Some dust was collected close to wagon roads, where it was raised by 

 passing vehicles and sifted as it fell by gentle winds. In dust of this 

 kind, which fell 5 feet from the road, 23 per cent was fine sand and 11 

 per cent was composed of still coarser grains. In dust which fell 10 

 feet farther away there was only a little over 4 per cent of the coarse 

 grades. In this sample very fine sand forms 31 per cent. Ten feet still 

 farther out this grade is represented by less than 10 per cent. These 

 grades evidently easily settle out of gentle atmospheric currents. Of 

 particles which are less than one sixty-fourth of a millimeter in diam- 

 eter there are only small quantities, presumably because such particles 

 tardily settle even in ordinary low winds. 



Dust which was swept by the wind from the banks and the bottom 

 lands of the Minnesota Kiver and lodged on the ice in its channel shows 

 about the same composition as the average of the last samples. 



Two samples of dust were collected in houses 4 miles away from 

 blown sandy fields in IvTorth Dakota. 



List of Samples in Table 26 



264. Dust in a house four miles from a blown field, North Dakota. 



265. Dust in a school-house four miles from a blown field, North Dakota. 



266. Collected in a running railroad coach after a sandstorm in Arizona. 



267. Collected in a running railroad coach in southern Minnesota. 



268. Collected in a running railroad coach in Nebraska and Kansas. 



269. Collected in a running railroad coach in New England. 



270. Collected in a running railroad coach in North Dakota and Montana. 



271. Collected in a running railroad coach in the Rocky Mountains and the 



Cascades. 



272. Collected in a running railroad coach in Utah. 



273. Collected in a running railroad coach in North Dakota after a storm. 



274. Collected in a running railroad coach in North Dakota. 



275. Collected in a running railroad coach in western Minnesota. 



276. Collected in a running railroad coach in eastern Colorado. 



277. Collected in a running railroad coach in Kansas. 



278. Collected in a running railroad coach in Idaho and Washington. 



279. From a window-sill in a house in Yuma, Arizona. 



280. Volcanic dust from snow in Norway. 



281. Dust taken 5 feet from a wagon road near Baltimore, Maryland. 



282. Dust taken 15 feet from a wagon road near Baltimore, Maryland. 



283. Dust taken 25 feet from a wagon road near Rock Island, Illinois. 



284. Dust taken 25 feet from a wagon road near Baltimore, Maryland. 



285. Dust collected from the ice on Minnesota River. 



