144 SOCIAL INVOLUTION 



governing power IV 11 into the bands of vigorous north, -ni 

 barbarians. The ci\ ilixalion of Rome declined. ' 



We have now examined two kinds of climatic change, 

 latitudinal and pulsatory. It remains to consider the 

 influence of more local changes, what we commonly < ,ill 

 the weather. Careful investigation has confirmed Un- 

 popular belief that clear, cool weather is invigorating. 

 Dexter, in his book, "Weather Influences, " has made 

 a study of the influence of various meteorological con- 

 ditions upon the conduct of school children, upon the 

 occurrence of crime, and upon the number of errors made 

 by bank clerks. In damp, muggy weather people feel 

 disagreeable and suppose themselves ready to do all sorts 

 of evil things. As a matter of fact they do not do them, 

 for the vital functions are so far depressed that there 

 is no surplus energy to spend in doing anything very 

 active, either good or bad. Dry, windy days stimulate 

 the vital processes, unless it be exceptionally warm, and 

 create a surplus of energy which finds expression in work 



i The evidence employed to substantiate the theory of pulsatory climatic 

 changes is roughly of four kinds. The first kind consists of physiographic 

 phenomena such as river terraces, lake strands, denuded mountain 

 slopes, desiccated springs, and rivers whose salinity has increased. A sect. ml 

 kind consists of archeological phenomena, ruins of great cities in places 

 whose supply of water is not now one-tenth large enough to support nin-h 

 a population as once existed. A third kind of evidence consists of his 

 toric accounts of famines, of old roads across the des.-rt which to-day are 

 impassable. Finally, evidence is basod UJH.M plant life. The thickness of 

 the rings of annual growth in old trees ha- IM-I-H f..und to !>< proportional 

 to the amount of rainfall. Huntin^ton m-a-iired the rings of annual growth 

 of 450 of the Big Trees of California, Sequoia gigantea, and plotted the 

 curve of climatic pulsation indicated by variation in these rings. The 

 trees which were measured were from 230 to 3200 years old. Eighty were 

 over 2000 years old and three more than 3000 years old. The data was, 

 therefore, quite comprehensive. The curve showed a remarkable verifica- 

 tion of the theory of pulsatory climatic change. The dry periods corre- 

 sponding with the periods of desiccation shown by other phenomena. See 

 "Changes of Climate and History." 



