E. Loomis — Areas of low pressure. 5 



Comparison of Storm tracks toith Wind directions, over the 

 Atlantic Ocean. 



Longi- 

 tude. 



Latitude 



of storm 



tracks. 



Direction 

 of storm 

 tracks. 



Latitude 



of wind 



directions. 



Direction 



of 



wind. 



Difference 



of 

 latitude. 



Wind most 

 northerly. 



60° 



46-9° 



N. 67-0° E. 



425° 



X. 79-3° W. 



4-i° 



-33-7° 



50 



48-9 



637 



42-5 



S. 85-2 W. 



6-4 



-21-5 



40 



51-3 



667 



47-5 



S. 61-6 W. 



3-8 



+ 5-1 



30 



53-9 



72"2 



47-5 



S. 73-5 W. 



6-4 



- 1-3 



20 



54-9 



81-5 



50-0 



S. 65-2 W. 



4-9 



+ 16-3 



10 



55-5 



86-2 



52-5 



S. 58-6 W. 



3-0 



+ 27-6 



Column 1st shows the longitudes for which the comparisons 

 are made ; column 2d shows the latitude of the points to which 

 the direction of the storm tracks corresponds ; column 3d 

 shows the average direction of the storm tracks for the months 

 of January, April, July, and October ; column 4th shows the 

 latitudes corresponding to the wind directions; column 5th 

 shows the direction of the wind for the given latitudes and 

 longitudes ; column 6th shows the differences of latitude be- 

 tween the points to which the storm tracks correspond, and 

 those to which the wind directions correspond ; column 7th 

 shows the difference between the average direction of the wind, 

 and the average direction of the storm paths for the points of 

 comparison. 



It will be seen that there is an average difference of nearly 

 five degrees between the latitudes of the points for which the 

 wind directions are given, and those to which the storm tracks 

 correspond. I have endeavored to determine the proper correc- 

 tion of the wind directions for this difference of latitude, but 

 the corrections appear so questionable that I have made no use 

 of them. 



We see that for the middle of the Atlantic Ocean near the 

 parallel of 50° the average direction of storm paths corresponds 

 very closely with that of the average progress of the wind ; but 

 in the western part of the Atlantic, the average course of storms 

 is 30 degrees more northerly than that of the wind, while in the 

 eastern part it is nearly 30 degrees more southerly. 



I next made a similar comparison for twelve of the Signal 

 Service stations in the northwestern part of the United States, 

 between the Rocky Mountains and the meridian of 90° from 

 Greenwich, for the three winter months for the ten years from 

 1873 to 1882. The wind directions were deduced from the 

 sum of the observations for each of the eight principal points of 

 the compass and the direction of the storm paths on the Signal 

 Service maps was measured with a protractor. The following 

 table shows the result of this comparison. Column 2d shows 

 for each of the stations the mean direction of the wind ; column 

 3d shows the average direction of the storm paths ; and 



