254 BOARD OF AGRICULTURE. 



supply the rivulets from which the great water-courses draw 

 their supply. The water falling on a tract of land stripped 

 of its covering of woods is rapidly evaporated by the summer 

 sun, or in winter rushes off over the surface of the frozen 

 ground to the nearest water-course, converting this for the 

 time being into a roaring torrent. In a country properly 

 wooded, the result would be exactly opposite. The summer 

 rain, falling on the ground, protected by the forest from 

 evaporation, is held as in a sponge, slowly but surely find- 

 ing its way to the water-courses, while the melting snows and 

 winter rains gradually soak into the soil which in the forests 

 is never so deeply frozen as in the open ground. This is 

 no mere theory, but a fact of which the proof is, alas ! too 

 easily found, and too convincing. It is a subject of common 

 remark in the country, that brooks which formerly ran 

 throughout the year, are now dry save after the autumn rains, 

 or the melting of the snows in spring, when they become 

 raging torrents, carrying off to the sea in a few days the 

 water which formerly supplied them with a moderate but 

 constant flow throughout the summer. Unfortunately, no 

 observations of the flow of the great rivers in the United 

 States have been made, covering a period of time of sufficient 

 length, to enable us to draw any conclusions in regard to it. 

 But in Europe this subject has received more careful investi- 

 gation. Herr Wex, at the recent yearly meeting of the Geo- 

 graphical Society of Vienna, demonstrated that the average 

 level of the river Elbe had fallen seventeen inches ; that of the 

 Rhine, over twenty-four inches ; that of the Vistula, twenty- 

 six inches ; and that of the Danube at Orsova, as much as 

 fifty-five inches during the past fifty years. Accompanying 

 this fall in level, there was also shown to be a constantly 

 increasing diminution of the discharge from springs. In- 

 stances, though of less general importance, are not wanting 

 near home. " There * is a good illustration of the effects of the 

 destruction and reproduction of forests in drying up and 

 restoring ponds in my immediate neighborhood. Within 

 about one-half mile of my residence 'there is a pond upon 

 which mills have been standing for a long time, dating back, 

 I believe, to the first settlement of the town. These have 



* Trees of America. R. U. Piper, Boston, 1855. 



