CLIMATE OP HISTOllIC TIMES 539 



inches and a temperature of 62.44°. A difference of 40 per cent in rain- 

 fall was accompanied by a difference of only 0.4° F. in temperature. 



The facts set forth in the preceding paragraphs seem to show that ex- 

 tensive changes in precipitation and storminess can take place without 

 appreciable changes of mean temperature. If such changed conditions 

 can persist for ten years, as in one of our examples, there is no logical 

 ]-eason why they can not persist for a liundred or a thousand. The evi- 

 dence of changes in climate during the historic period seems to suggest 

 changes in precipitation much more than in temperature. Hence the 

 strongest of all the arguments against historic changes of climate seems 

 to be of relatively little weight, and the pulsatory hypothesis seems to be 

 in accord with all the known facts. 



DIVERSITY OF CHANGES OF CLIMATE IN DIFFERENT REGIONS 



Before the true nature of climatic changes, whether historic or geo- 

 logic, can be rightly understood another point needs emphasis. When the 

 pulsatory hypothesis was first framed, it fell into the same error as the 

 hypotheses of uniformity and of progressive change — that is, the assump- 

 tion was made that the whole world is either growing drier or moister 

 with each pulsation. A study of the ruins of Yucatan, in 1912, and of 

 Guatemala, in 1913, as is explained in "The Climatic Factor," has led to 

 the conclusion that the climate of those regions has changed in the oppo- 

 site, way from the changes which appear to have taken place in the desert 

 regions farther north. These Maya ruins in Central America are in many 

 cases located in regions of such heavy rainfall, such dense forests, and 

 such malignant fevers that habitation is now practically impossible. The 

 land can not be cultivated • except in especially favorable places. The 

 people are terribly weakened by disease and are among the lowest in Cen- 

 tral America. Only a hundred miles from the unhealthful forests we find 

 healthful areas, such as the coasts of Yucatan and the plateau of Guate- 

 mala. Here the vast majority of the population is gathered, the large 

 towns are located, and the only progressive people are found. Neverthe- 

 less, in the past the region of the forests was the home of by far the most 

 progressive people who are ever known to have lived in America previous 

 to the days of Columbus. They alone brought to high perfection the art 

 of sculpture ; they were the only people who invented the art of writing. 

 It seems scarcely credible that such a people would have lived in the worst 

 possible habitat when far more favored regions were close at hand. There- 

 fore it seems as if the climate of eastern Guatemala and Yucatan must 

 have been relatively dry at some past time. The Maya chronology and 

 traditions indicate that this was probably at the same time when moister 



