1 84 EVOLUTION OF THE EARTH 



the answer to a series of questions recently sent out by the 

 writer. As Dr. W. D. Matthew, one of the most careful stu- 

 dents of the matter, says, "I should demand proof before I 

 would admit that there has been no change within 2,000 

 years." 



The weakness of the hypothesis of climatic uniformity is 

 indicated by a consideration of the strongest argument in its 

 favor. It runs thus: The palm and the vine grow together 

 only within a most limited range of temperature. Today they 

 grow together in essentially the same places as 2,000 or 3,000 

 years ago. Hence no change of temperature and no change 

 of climate. This argument is weak in two respects. In the 

 first place, students of the Glacial Period agree that at the 

 height of the last epoch of advancing ice, perhaps 30,000 years 

 ago, the mean temperature of the earth was only about 10, or 

 at most 20 F., lower than now. On that basis an historic 

 change of climate one-tenth as great as the enormous change 

 since the height of glaciation would mean a change of only one 

 or two degrees in temperature, an amount too small to detect 

 by means of vegetation. In the second place, the fact that 

 there has been no appreciable change of temperature in his- 

 toric times does not mean that there has been no change in the 

 distribution of rainfall. The records of the United States 

 Weather Bureau show that during the years 1875 to 1884 the 

 region from Galveston to New Orleans had 40 per cent more 

 rainfall than during the ten years from 1890 to 1899. The 

 difference in temperature between these two periods was only 

 0.42 F. Curiously enough, the wet period was the warmer, 

 although in other cases the reverse has been true. If such 

 important changes in the distribution of rainfall can occur in 

 our own day with almost no change in temperature, there is 

 no reason why much larger changes may not have occurred 

 similarly in the past. That such changes have occurred is indi- 

 cated by almost innumerable waterless ruins like those which 





