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 chiefly to the temperature and the prevalence of 

 droughts 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 amount of 

 precipitation but by the water reaching the streams more 

 rapidly ; and it often happens that barren regions suffer 

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

 noted, however, that many of the unusual floods of late 

 years have been caused by very heavy rainfalls on account 

 of the abnormal conditions which we have been consider- 

 ing, but the results have been more marked in scantily 

 wooded regions than they would have been had the hills 

 been covered with 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 afforded us for observation while the evil effects of 

 forest destruction are too common. Whole districts which 

 once were rich and productive have become dry and bar- 

 ren, their streams have dwindled to mere brooks, except 

 after heavy rains, when they rise rapidly and sometimes 

 overflow and the soil is gradually washing away from the 

 hills. The effect in temperature varies somewhat with 

 the surrounding conditions. The clearing of forest lands 

 in Germany had the effect of raising the temperature. In 

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

 perature has been 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 IN ST. BULLETIN, VOL. XVIII. 6 



