42 C. A. SCHENCK. 



3. Any local modifications of temperature and humidity 

 caused by forest covering, buildings in cities etc. could not 

 extend upward more than a few hundred feet, and in this 

 stratum of air, saturation rarely occurs even during rainfall; 

 whereas precipitation is the result of conditions that exist at 

 such altitudes and on such a grand scale as not to be con- 

 trolled or affected by the small thermal irregularities of the 

 surface air. 



4. During the period of accurate observations the amount 

 of precipitation has not increased or decreased to an extent 

 worthy of consideration. 



5. Floods are caused by excessive precipitation, and the 

 source of the precipitation over the central and eastern portions 

 of the United States is the vapor borne by the warm southerly 

 winds from the Gulf of Mexico and the south Atlantic Ocean. 



At times spring floods occur from the rapid melting of unu- f 



sually large quantities of accumulated winter snows, and, as 

 Chittenden has pointed out, such floods come oftener from 

 the forest than from the open. 



6. The disastrous effects of soil erosion, however caused, 

 appear to have been exaggerated, and erosion is not always 

 an unmixed evil. 



7. Compared with the total area of a given watershed, that 

 of the headwaters is so small that, except locally in mountain 

 streams, their runoff would not be sufficient to cause floods, 

 everi if deforestation allowed a greater and quicker runoff. 

 Granting, for the sake of argument, that deforestation might 

 be responsible for general floods over a watershed, it would 

 be necessary in order to prevent them to reforest the lower 

 levels with their vastly greater areas, an impossibility unless the 

 lands are to be abandoned for the use of men. 



r 8. The runoff of our rivers is not materially affected by any 

 other factor than the precipitation, except that the forest, by 

 facilitating evaporation and entirely restraining small or mo- 

 derate rainfalls during the dry weather, may slightly intensify 

 low water conditions. 



9. The high waters are not higher, and the low waters are 

 not lower than formerly in fact, there appears to be a ten- 

 dency in late years toward a better low water flow in summer. 



