16 E. Loornis — Contributions to Meteorology. 



This table appears at first view to present a discouraging 

 medley of anomalies, but some of the anomalies may appear less 

 formidable after a careful examination. It seems highly pro- 

 bable that the slow progress of storm areas in southern Asia is 

 partly due to the small velocit}^ of the winds of that region. It 

 is not obvious why storms should travel more rapidly near the 

 West India Islands than in the China Sea. It is possible that 

 this anomaly may disappear when the mean velocity of the wind 

 has been determined by a more extended series of observations. 



It seems to be established that over the Atlantic Ocean the 

 mean velocity of the wind is considerably greater than the rate 

 of progress of storms. This inequality is strikingly exhibited 

 in numerous cases. Over this Ocean, we frequently find an area 

 of low pressure, 2000 miles or more in diameter, with a pres- 

 sure of about 28 inches at the center, attended by winds blow- 

 ing with hurricane violence, while from day to day the center 

 of the low area makes little or no progress eastward, showing 

 that the movement of the atmosphere which corresponds to the 

 average system of circulation, is almost entirely interrupted over 

 this ocean. 



The most noticeable anomaly shown in the preceding table is 

 however presented by the United States, where the mean 

 velocity of the wind is only one-third as great as over the 

 Atlantic Ocean, but storms travel with nearly double velocity. 

 This anomaly may be partly explained if we admit that the 

 progress of storms is determined, not by the wind which pre- 

 vails in close contact with the earth's surface, but by that which 

 prevails at an elevation of several hundred feet, where the 

 velocity is probably much greater than at the earth's surface. 

 The same anomaly however is found when we compare the 

 storms of the United States with those of Europe. In northern 

 Europe the surface winds have a velocity greater than those of 

 the United States, and we may infer that the same is true for 

 elevations of 1000 or 2000 feet above the surface ; yet storms 

 in Europe advance with but little more than half the velocity 

 of those in the United States. There must then be a powerful 

 cause which accelerates the movement of storm areas in the 

 United States, and which does not operate in Europe or over 

 the Atlantic Ocean ; and apparently the same cause does not 

 operate in southern Asia, or in the West Indies, at least in an 

 equal degree. This cause (or one of these causes) is probably 

 the precipitation in the form of rain or snow which, in the 

 United States, usually takes place on the east side of a storm 

 area, greatly in excess of that on the west side, as I have shown 

 in my seventeenth paper ; but for the interior of Europe the 

 same does not appear to be true, or certainly not in an equal 

 degree, as I have shown in my twelfth paper. 



