170 



MICHIGAN ACADEMY OF SCIENCE. 



Coates informs me, on authority of Mr. George H. Porter, of Sparta^ 

 that a similar storm occurred at that place in 1873. On February 18, 

 1896. ]\Ir. Herman P. Thomas of Cassopolis witnessed a dustfall there. 

 He weighed a collection from a measured space from which he computed 

 245 pounds per acre, a quantity greatly exceeding that indicated by 

 measurements in the recent instance. 



The Monthly AVeather Review of January, 1895, contains a detailed 

 account of a dust storm in parts of Indiana and Kentucky with results 

 of careful analyses of numerous sami)les of the material. 



In all these instances the material seems to have been nearly or quite 

 identical with that of the recent storm. 



\y^<^\>i. 



1. A map showing approxlniatelv the extent of the dust shower in western Michigan,. 



January 27, 1902. 

 Places at which the dust is Itnown to have fallen are marked with x. 

 Extent from north to south along the lake shoi-e about GO miles. 

 Greatest extent eastward from shore about oO miles. 



Average amount of dustfall per square foot based on three measurements 2.058 grams. 

 Estimated amount of dust deposited on one scpiare mile, ii.'.i'-i tons. 

 Amount computed for area of 1 ,('.0() s(iuare miles, about ]<),000 tons. 



In attempting to explain the raising and transporting for so great a 

 distance of this mass of soil all readily available data were acquired 

 relating to (1) wind directions and velocities, (2) distribution of loess, 

 (3) snow covering in -the loess regions. The officials of the U. S. 

 Weather Bureau both at Washington and at the Grand Haven station 

 kindly furnished an abuudancc of meteorologiral data by maps and 

 otherwise. These were diligently studied to tind indications of a possi- 

 ble bare spot of loess where the prevailing wind could have done the 

 work. 



