THE CLIMATOLOGY OF THE UNITED STATES. 49 



control of man are the forests. These have an important 

 bearing on the climate of a place and their wholesale des- 

 truction is apt to create an unfavorable change. This is 

 confined cliiefly to the temperature and the prevalence of 

 dronghts and floods. In the case of the latter in a defor- 

 ested region, the efFect, so far as the destruction of the 

 forest is concerned, is not produced by an extra anionnt of 

 precipitation but b}^ the water reaching the streams more 

 rapidly ; and it often happens that barren regions suflfer 

 most from floods, other things being equal. It should be 

 iioted, however, that many of the unnsnal floods of late 

 years have been caused hj very heavy rainflills on aecount 

 of the abnormal conditions which we have been consider- 

 ing, but the results have been more niarked in scantily 

 wooded regions than they would have been had the hüls 

 been covered witli a heavy growth of timber. It has been 

 quite strongly maintained by some authorities that forests 

 do not actually cause more rain ; but if they do not in a 

 direct way, they do indirectly, and numerous examples 

 are afibrded us for Observation while the evil effects of 

 forest destruction are too common. Whole districts which 

 once were rieh and productive have become dry and bar- 

 ren, their streams have dwindied to mere brooks, except 

 after lieavy rains, when they rise rapidly and sometimes 

 overflow and the soil is gradually washing avvay from the 

 hüls. The effect in temperature varies somevvhat with 

 the surrounding conditions. The Clearing of forest lands 

 in Germany had the eff'ect of raising the temperature. In 

 England the same result followed, but in Iceland the tem- 

 perature has ]:)een lowered. It may be said, however, as 

 a rule that a forest equalizes the annual temperature as 

 well as the distribution of the rainfall. 



About ten years ago I wrote an article, calling atten- 

 tion to the importance of united work for the preservation 



ESSEX INST. BULLETIN, VOL. XVIII. G 



