214 ACTION OF FORESTS ON THE SUHPACE-FLOW OP RAIN WATER. 



M. Conte-Granchamps, Ingenieur en Chef des Fonts et Chmissees, 

 has established by direct experiment, made with precision and with 

 the greatest care in the forests of coniferous trees situated in the 

 regions of the Loire and the Alps : — 



" 1. That existing sources have ceased to flow on the destruction 

 of forests. 



" 2. Thai these identical springs have re-appeared along with 

 vegetation. 



" 3. That the discharge from a water-course, the bassin de reception of 

 which is wooded, varies from one to two ; whilst that of another water- 

 course, proceeding from a bassin de reception which is devoid of woods, 

 all things else being equal, varies from one to six. 



" 4. Finally, that the reboisement of one hectare, or two and a half 

 •acres, will increase the discharge from the spring sixteen cubic 

 metres daily ; whilst gazonnement, or covering it with herbage, in the 

 sS,me circumstances increases the discharge by four cubic mfetres." 



And on the other hand, M. d'Arbois de Jubainiville, in reply to an 

 appeal made to its readers by the Revue des Eaux et Forets, for 

 information respecting the influence of forests over the water system, 

 expresses himself as follows : — 



" Several forest clearings have been executed in the canton of 

 Vaucoul6urs. I have tried to discover what changes have been 

 produced in the springs. All the springs of this territory have their 

 rise in the middle strata of the oolitic system. And the forests above 

 are treated as are usually coppice and timber forests. 



" In the territory belonging to the commune of Taillancourt the 

 spring of Vaux-de-Bure had never dried up so long as the plateau 

 which supplied it was shaded by the forest of Vaux-de-Bure, but 

 ever since the half of that forest was cut down every summer the 

 spring has ceased to flow. The clay bed underlying the spring is at 

 no great depth ; it lies within a few metres of the surface throughout 

 the greater part of the basin of supply. 



" In the commune of Sauvoy, near the Mayoralty, a perennial 

 spring became ephemeral when a wood was cut down which covered 

 the side of a hill, at the foot of which the spring was situated. 



" On the contrary, in the commune of Mopsigny-les-Vaucouleurs, 

 the partial clearing of a hill overhanging the spring has not interfered 

 with the outflow, the fountain of supply seeming to be very deep. 



"I have also examined the efi'ects of exploitation where felling 

 takes place in the basin of the springs, giving thus free access to 

 to them of sunshine and wind. 



