LOESS-DEPOSITING WINDS IN LOUISIANA 541 
are from northerly directions, 16 per cent from southerly directions, 
Ir per cent from easterly directions, and 43 per cent from westerly 
directions. It should be noted that only the highest winds are 
included in the data given above. Undoubtedly the high winds are 
effective dust carriers, but loess is so fine grained that it could 
doubtless be carried by ordinary winds, other things being favorable. 
Fig. 3, which shows the winds of all velocities, probably is more 
significant than Fig. 4, which shows only a part of the high winds. 
Remembering the much greater thickness and width of the eastern 
loess belt, it would seem that the present winds would not be com- 
petent to account for the disparity between the eastern and western 
loess belts. This is certainly true so far as occurrences are con- 
cerned, and there is no reason to believe that either the persistence 
or velocity of winds from any one direction are especially notable. 
During loess-depositing times westerly winds must have been more 
predominant than at present. The present southerly winds would 
seem to be competent to deposit the greater thickness of loess at 
Avoyelles Prairie and Sicily Island. Obviously more observations 
of loess thickness on isolated areas are needed before positive con- 
clusions can be drawn as to the efficiency of southerly winds. 
SUMMARY 
(1) The greater efficiency of westerly winds in the southern loess 
belts is shown by (a) the greater width and thickness of the eastern 
loess belt and (6) by the higher percentages of lime, potash, and 
phosphoric acid of the soils of the western belt. (2) The greater 
thickness of loess on the southern sides of two isolated loess areas 
indicates that southerly winds were more efficient in this region 
than northerly winds. (3) From the meager data available it 
would seem that westerly winds were more frequent and effectual 
in loess-depositing times than at present. 
