i8o THE POPULAR SCIENCE MONTHLY, 



utes ; hardly bad it begun wben tbe torrent of St. Pbalez became 

 awful ; it filled the ravine from bank to bank, seizing and carrying 

 off rocks which had been used to form a road, which was considered 

 safe against all contingencies. At the same time, that of Combe 

 d'Yeuse and all those traversing wooded lands remained dry or car- 

 ried a comparatively insignificant quantity of water. 



The forest conservator describes a second scene on the same spot 

 in the following October. In a few minutes after the rain began, the 

 torrent of St. Phalez gushed forth with the same destructive effect as 

 before. But after an entire day of rain a small stream appeared com- 

 ing down the Ravine d'Yeuse, which increased for three days and then 

 for two declined. The only damage done was to a little footpath. 

 " Thus we have," says the reporter. " two torrents very near to each 

 other, and exposed to the same conditions, except that the basin 

 drained by the one comprises fifty hectares of cultivated lands, that 

 of the other two hundred and fifty hectares of woodlands. The first 

 receives and allows to flow away the waters of the greater part of a 

 storm in a few hours at most, causing thereby considerable damage ; 

 the second, which has received a greater quantity of rain, stores it 

 keeps it for two days evidently retaining a portion of it, and takes 

 three or four days to yield up the surplus, which it does in the form 

 of a limpid and inoffensive stream." 



So also in the colder latitudes, where during the wintry months 

 the moisture of the atmosphere is precipitated in the form of snow 

 and accumulates often to a great depth, the conservative influence of 

 the forest is very obvious. The temperature of the woods is warmer 

 in winter, as it is cooler in summer, than that of the open ground. 

 Sheltered from the winds and, to a considerable degree, from the cold, 

 the snows themselves forming a protecting covering, the earth seldom 

 freezes in the forest, and the warmth from the ground below gradu- 

 ally melts the snow and so feeds the springs and streams as to main- 

 tain in them an equable flow. As the warmer sun and wind of ad- 

 vancing spring-time begin to heat the surface of the ground, the 

 screen of the trees prevents their influence from being so sensibly felt 

 in the woods as in the open fields. The result is, that the snows dis- 

 solve gradually, and the resultant water, sinking in the first place and 

 for the most part into the spongy, leafy soil, flows away gently, as do 

 the rains of summer-time, into the valleys and fields below. But, when 

 the forests have been removed, the case is very different. The snows, 

 no longer screened from the sun's rays and the warm winds by the 

 interposed foliage or even the naked trunks of the trees, are rapidly 

 dissolved, often before the earth beneath or the ground over which the 

 waters must flow has been unlocked from the wintry frosts. As a 

 necessary result, thousands of rivulets are formed almost at once, 

 which are precipitated into the adjacent streams, whose rapidly in- 

 creased volumes are hurried to the larger streams below, and thus we 



