CLIMATE OF HISTORIC TIMES 549 



conclusions as to variations of temperature. He finds that in Kew Mex- 

 ico, Arizona, and southern California variations of temperature "display 

 a striking preference to belong to the inverse type, and that in Pennsyl- 

 vania and Oregon the direct type must predominate." By direct he 

 means that the temperature rises and falls in harmony with that of Are- 

 quipa, whose cycle of two or more years is taken as the standard of the 

 pleions and antipleions of temperature which seem to arise from varia- 

 tions in solar radiation. 



Asia. — In the Old World it has not been possible to work out the matter 

 so carefully as in the New, partly because the problem is more complex 

 and partly because there is no uniform series of records easily available. 

 In Asia most authorities, as is indicated by Gregory's map, believe that 

 the climate of the center of the continent has changed. These changes 

 appear to have been of essentially the same sort as those of the south- 

 western United States, as is indicated by the trees of California, the 

 fluctuations of the Caspian Sea, and other evidences which form the basis 

 of the curves of figure 13. Here, then, just as in the United States, the 

 distribution of past climatic changes agrees with what we should expect 

 if the changes were due to variations in the sun. In western Asia and 

 the Mediterranean region I am strongly inclined to the same opinion for 

 •reasons already stated. Another reason for holding this view is that in 

 its relation to the continent and in its general climatic conditions this 

 area closely resembles the portion of the United States where the rainfall 

 seems to have diminished. 



Europe. — In Europe it will within a few years be possible to make maps 

 like the two of the United States shown in figures 16 and 17. Meanwhile 

 we must turn to other lines of evidence. In that continent, as we have 

 seen, periods of sun-spots appear to be characterized by continental con- 

 ditions with dry winters and wet summers. At such times the barometric 

 gradients are steepened, so that storms in the peripheral regions tend to 

 be more violent than at times of sun-spot minima. The only evidence 

 which we have as to changes of climate in Europe suggests that such con- 

 ditions prevailed at certain times many centuries ago. Tycho Brahe, 

 during the years 1582-1597, made meteorological observations on a little 

 island in the !N"orth Sea. He recorded the direction of the wind and the 

 occurrence of days characterized by cloudiness, rainfall, sun, and hail. 

 His data have been compared with those of modern times, and the results 

 are summed up in Hann's Klimatologie, volume 1, pages 346-347. The 

 general conclusion is that there is some indication that in Tycho Brache's 

 day the climate of western Europe was a trifle more continental than 

 now, but, as Hann points out, the difference between then and now was 



