658 POPULAR SCIENCE MONTHLY. 



In nearly every instance where these disturbances have been 

 described some mention is made of the quantity of the material 

 transported by the atmosphere. Nevertheless, it is exceedingly 

 difficult to make any definite estimate in this direction, as no 

 actual measurements have been made by any of the observers. 

 But a number of the accounts are such that comparisons can be 

 made between the phenomena described and some other instances 

 of dust transportation which have come to the writer's notice, 

 and which have furnished some quantitative estimates. The 

 results of such comparisons are here given for what they are 

 worth. In several cases the effect of the dust on the trans- 

 parency of the atmosphere is noted. It is thus stated that — " It 

 gives the sun a sickly color." — " It is dense enough to obscure 

 the mountain ranges from view " (at a distance of from five to 

 ten miles), — "It is sufficient to allow the sun being viewed with 

 the naked eye." — " Immense quantities of sand and dust filled the 

 air, until the sun became so obscure that it could only be seen as 

 a round ball, at which one could gaze with impunity." 



During a high wind on the 25th of March, 1895, following a 

 dry season, the atmosphere over the northern part of Illinois and 

 over a part of Iowa had an appearance which corresponded to 

 the instances here described. The storm lasted about three hours, 

 and during that time an apparatus for collecting dust from the 

 atmosphere was suspended at an elevation of about a hundred feet 

 above the ground back of the bluffs of the Mississippi River at 

 Rock Island, 111. This apparatus was so arranged that dust could 

 not be taken from a current of air more than a tenth of a square 

 foot in cross-section. It is possible that the actual current was 

 not more than a tenth as large as this. The quantity of dust col- 

 lected was about two ounces. The wind velocity for the three 

 hours was thirty miles per hour. This indicates that the atmos- 

 phere on that day carried a load of one hundred and sixty, or 

 possibly sixteen hundred, tons of dust to the cubic mile of air. 



Some of the notes refer to the accumulation of dust and sand 

 in dwelling houses and other buildings, viz. : " Merchants closed 

 their doors to protect their goods" (from the dust). — "The quan- 

 tity of sand swept from houses (by housekeepers after a storm) 

 showed the severity of the storm the two previous days. The 

 sand penetrated every nook and corner." — " The pattern of the 

 carpet may be obliterated ; drifts have been formed on the floor 

 from one to two inches in depth." — " The dust filled every resi- 

 dence completely [!] covering up everything while it lasted." — 

 " The wind hurled a few quarter sections [!J of rich loam into 

 the residences and business houses." 



Blown dust is a general and familiar nuisance to housekeepers 

 over the entire West. A minimum estimate, verified by direct 



