ARCTOWSKI. CHANGES IN DISTRIBUTION OF TEMPERATURE 87 



of the equideparture curves is the same. A seesaw movement would ex- 

 plain the transformation ; but, as will be seen later, such an explanation 

 is not satisfactory. 



The map of 1908 (Fig. 30) indicates a simple displacement of the 

 pleion towards the north. The shape of the pleion remained practically 

 the same and in the west an antipleionian wave, following the movement, 

 advanced over the continent. The pleion has two crests, one going from 

 Alberta towards Kentucky, with the departures of -|- 2°.6 in Calgary, 

 -f- 2°.l in Medicine Hat, + 1°.9 in Bismarck, Minneapolis and Cincin- 

 nati, and a second wave following a perpendicular direction along the 

 Atlantic coast in the New England States (-(- 1°,6 in Boston and New 

 Haven). Curiously enough, farther south, a depression in the pleion is 

 noticeable, the departure being -f- 0°.5 at Eichmond, Raleigh and Char- 

 lotte, and only + 0°.3 in Lynchburg. On the Atlantic there is an anti- 

 pleion, the quasinormal line going from Jupiter, Fla., towards Halifax, 

 In Bermuda, the departure is — 0°.9. 



Finally, the map of 1909 (Fig. 31) shows the disappearance of the 

 northwestern crest of the pleion under the influence of the advancing 

 antipleion, whose two distinct centers moved from Eureka towards Battle- 

 ford and from Independence toward Valentine. The pleion of 1908 has 

 been reduced to a wave extending from Nova Scotia towards Texas. The 

 most positive departures are + l°.l in Sydney, Grand Manan and Char- 

 lottetown, and -|- 1°.7 in Fort Worth, Tex. 



To gain a more precise knowledge of the displacements of the pleions 

 and antipleions, which took place during the years 1900-1909, I made 

 consecutive maps and consecutive curves. I will examine separately the 

 results gained by the study of the curves and of the maps. 



Consecutive Maps 



The annual departures of 175 stations were utilized to draw the maps 

 I have just described. To obtain similar consecutive maps would have 

 involved a great amount of purely clerical work. I simplified the task 

 by omitting the Canadian data and taking only the means of the twenty- 

 one districts into which the United States are divided in the columns of 

 data published in the "Monthly Weather Review." I copied the monthly 

 means for the years 1900-1909 for these districts, then calculated the 

 consecutive totals, then the individual means and finally the departures 

 of these means from the normal values. This last operation was some- 

 what arbitrary and I would certainly have done better by taking the de- 

 partures from the ten-yearly means. 



