26 



ing industry more tban keep pace with tlie substitution of other materi- 

 als, and a rising price of wood is likely to be the result. 



But forests occupy an entirely different position from all other forms 

 of natural wealth, and a far more fundamental one. They determine, 

 to a very large extent, climatic and hygienic conditions, and, through 

 these, the prosperity of industry and the distribution of disease and 

 health. The functions of forests in modifying climate and soil are so 

 fully and ably presented in the various reports and bulletins of the De- 

 partment of Agriculture, and in the proceedings of the various Forestry 

 Associations, that the merest suuimary of the important facts will suffice 

 for our present purpose. 



Whether the presence of forests actually inereases the total amount 

 of rain-fall within any great region may still be a subject for dispute, 

 but all authorities agree that forests produce a much more equable dis- 

 tribution of moisture throughout the year than exists where they are not 

 found. In a treeless district, particularly if it be hilly, the rain glides 

 oft into the rivulets and into the rivers, scarcely moistening the ground 

 below its surface. The burning rays of the sun, or the sweeping blasts 

 of air, cause the rapid evaporation of what may remain here and there 

 on the surface or may have penetrated a little way into the soil. A 

 few hours after the rain there are almost no signs that rain has fallen 

 at all. On the contrary, where there are forests the interlaced roots 

 of the trees and the mass of leaves above them act as a sponge, which 

 absorbs the water and holds it long enough to enable it to perform its 

 service of quickening animal and vegetable life. The water oozes and 

 trickles down through this spongy substance, and flows slowly away to 

 feed the springs and streams. The modifying action of great forests 

 on the distribution of moisture is both direct on the immediate region 

 lying about them, and indirect on distant localities, owing to their influ- 

 ence on the character of the streams and rivers which drain their areas. 



Where streams are not thus protected and modified at their sources 

 by forests they may become the cause of almost as much injury as ben- 

 efit. Owing to the fact that the water flows off so rapidly, the streams 

 become at one time raging torrents, sweei)ing everything before them 

 and inflicting an amount of damage which it requires much of the time 

 elapsing between floods to make good, while at another they dwindle 

 into insignificance, scarcely furnishing water enough for the flocks and 

 herds along their banks. Where the forests have been cleared from 

 the sources and banks of historic rivers the result has been an entire 

 change in the character of the streams. The history of the Rhine, 

 Ehone and Danube^ in this respect, is full of instruction for us, and if 

 alternating periods of drought and disastrous floods can not always be 

 directly traced to the removal of the forests, their aggravation and 

 frequency has been shown, even in this country, to be due to such re- 

 moval. 



This influence of forests on the character of our streams is a much 



