DISCUSSION AND ANALYSIS OF WINDS. 677 



but these are easily accounted for, if we remember that the period of observation 

 was short, mostly one year only, and that the climate of the Arctic regions is very 

 changeable ; still there are some differences in the direction of the winds which 

 can only be ascribed to their geographical position. Thus Northern Greenland has 

 the greatest prevalence of the true polar winds, northeast, and this is due in no 

 small degree to its proximity to Iceland, as well as to the open water of Smith's 

 Sound near a very cold continental area. 



The most northerly stations west of Smith's Sound, as Northumberland Sound 

 and Port Refuge, have the least amount of northern winds. This is, no doubt, 

 owing to their distance from Iceland, and, probably also, to a partly open sea to the 

 northward of them. If there is really an open sea in this direction, the pressure 

 there must be lower in winter than on the ice-bound straits of the Archipelago. 

 This would give rise to southerly winds to equalize the pressure, and thus explain the 

 greater number of these winds in Northumberland Sound and Port Refuge. They 

 do not prevail at these places, because the depression about Iceland is still felt 

 there as well as the depression which must exist on the open waters of Davis' 

 Strait and Smith's Sound. As the other stations of the Archipelago, except Mel- 

 ville and Dealy Island, are much nearer to Davis' Strait, they must feel its influ- 

 ence much more, while a great extent of islands and frozen bays and sounds sepa- 

 rate them from the northern partly open Polar Sea. 



The prevailing northerly winds in summer can be explained partly by the same 

 cause as those of winter — the low pressure about Iceland. It is true the barometer 

 near Iceland is not as low in summer as in winter. But in the Arctic zone of 

 America the pressure rises also, especially from February to May ; in the last-named 

 month it is the highest of the year in most of the stations of this region. 



It is probable that the pressure continues to rise in the circum-polar zone till 

 July, thus causing the northerly winds of Arctic America. At this season air is 

 also drawn towards the interior of North America, especially towards the region 

 between the Rocky Mountains and 95° W. Long. 



Arctic America is noted for its frequent calms in the colder part of the year — a 

 feature observed by nearly all who wintered in these regions. They are, however, 

 recorded in a very discordant manner in the journals of observations, showing 

 there was a great difference in the meaning of the word " calm." This want of 

 agreement has prevented a more elaborate discussion of this phenomenon, one of 

 the most important in regard to the movements of the atmosphere. 



Dr. Bessels has calculated the percentage of what he calls "absolute calms," for 

 the hours when a self-registering wind-vane did not indicate any movement of air 

 whatever, for the second winter-harbor of the U. S. Expedition, inider Capt. Hall, 

 at Polaris House or Lifeboat Gove. 



Hours of Absolute Calm in 1000. 

 November, 18T2, ^4 January, 1873, 298 March, 1813, 188 



December, " 47 February, " 79 April, " 179 



May, " 116 



Average for seven months, 140. 



I should remark, that in many of the stations the proportion of calms increases 



