83 ANNALS NEW YORK ACADEMY OF iiCIENCES 



At the begiiiiiiiig, 1 liad no intention of doing the work for all the years 

 and 8() I made the annual departures correspond to those given in the 

 "Monthly Weather Eeview." These departures are probably taken from 

 the means of the entire series of observations, and these means increasing 

 Or decreasing as the number of years taken into consideration increases, 

 the departures are necessarily not homogeneous. This lack of homo- 

 geneity has no importance, since I adjusted the values, for each year, so 

 they would correspond to the last annual departures (from the normals) 

 given in the annual summaries of the "Monthly Weather Eeview." 



The material which I have at hand consists of ten annual maps, giving 

 the distribution of the annual departures from normal means, and of one 

 hundred eight consecutive maps, showing the progressive changes of the 

 map of each year into that of the following year. 



First of all, I must say that comparing the ten annual maps, obtained 

 by utilizing district departures, with the ten detailed maps, described 

 previously, one has to admit that the method of grouping the results of 

 different stations to obtain regional averages is most inconsistent and 

 defective. One can imagine how inefficient our daily weather maps would 

 be if instead of utilizing the values given for individual stations we made 

 regional averages. Still, even such smoothed weather maps would give 

 some idea about the position of lows, and highs and cold waves could also 

 be located, though in a very vague and unsatisfactory way. 



On the consecutive maps I have drawn, the pleions and antipleions are 

 of course badly deformed and most interesting details are lacking, but 

 the more or less progressive displacements taking place can easily be 

 followed and the precise moments when the important changes in the 

 distribution of temperature occur are detected without great difficulty. 

 I will therefore compare the maps, simply in order to reach a better 

 understanding of the transformations of the annual departure maps from 

 one to another. 



1900-1901. The consecutive maps show that the antipleion of 1901 

 came from the south and progressed westward over the States. After 

 some minor oscillations of the quasinormal line,^® the upward movement 

 of the antipleion starts with the map of September, 1900,-August, 1901. 

 The annexed diagram shows the successive positions of this line on the 

 consecutive maps for the periods ending in August, September, October, 

 November and December, 1901 (Fig. 32). The western pleion remained 

 practically unchanged. 



28 These quasinormal lines deal with departures from normal values, and, evidently, 

 differ from those of the maps expressing the distribution of departures from ten yearly 

 means. 



