414 FORESTS AND THEIR CLIMATIC INFLUENCE. 



dimimitiou, from 1778 to 1835 in tlie first of tliese rivers, and from 1828 

 to 1830 iu the second, and that tliis diminntiou was so sensible tliat, 

 should it proceed at the same rate, it would be necessary at the lapse 

 of a certain period to change the construction of boats ; here, however, 

 statistical observations evince that this fact cannot be attributed to the 

 extermination of the forests of the mountains. In order to exi)lain it, 

 inquiry has been made whether the quantity of rain falling in the different 

 parts of Europe has not undergone a corresponding (•iminution, but the 

 hy])Othesis has not been sustained. In tact, since 1089, during which 

 interval the quantity of rain falling at Paris has been observed, a slight 

 augmentation, rather than any diminution, has been verified. Cesaris 

 has recognized the same increase for the city of Milan from 1703 to the 

 present epoch; and a similar result appears, in regard to Eochelle and 

 the basin of the Ehone. The supposition of a diminution of rain being 

 hence untenable, it has been surmised that possibly the number of rain- 

 falls may have changed, a conjecture founded on the generally admitted 

 fact that a great rain furnishes more water to the river courses than the 

 same quantity distributed over several days with intervals of dryness. 

 But the discussion of the observations has afforded no confirmation of 

 this view. It has been found necessary to fall back upon the changes 

 j)roduced in clinmtes by the progress of cultivation. 



It may happen, as has sometimes been the case, that concussions of 

 the earth dry up the sources of streams, but this is not common. A 

 great number of facts demonstrate, on the other hand, that the diminu- 

 tion is often an almost immediate sequence of extensive clearings. We 

 would point especially to the instance already cited of the water-courses 

 of Marmato. i^or are there other examples undeserving of a passing' 

 reference. The Eomans were able to bring to Orleans the waters of the 

 fountain of Etuvee, which at the present time is entirely dried up. Ex- 

 tensive excavations, made within a few years, have brought to light the 

 foundations of Eoman constructions where no source of water any longer 

 exists; a stream, moreover, to the east of Orleans, which contributed 

 to the defense of the city during the siege in 1128, and which was con- 

 siderable enough to turn mills, has completely disappeared. Now, on 

 that side of Orleans there were great forests, which have been cleared 

 away. In consequence of these clearings the wells of the city have 

 continued to yield less and less water, so that the municipal adminis- 

 tration has been obliged, within a few years, to incur an expense of 

 300,000 francs (800,000) in order to bring potable water from the source 

 of the Loiret. 



In the canton of Chatillon-sur-Loing there is a commune called Sainte- 

 Genevieve-des-Bois, which would appear to have been once a tract of 

 forest, but which presents to-day only small groves scattered here and 

 there. A stream formerly flowed at the foot of the town where at pres- 

 ent exists only its dried bed, never containing water except iu winter. 



In discussing the important question of the influence of disboscation 

 on water-courses, we arrive at the following- conclusions: 1. Extensive 

 clearings diminish the quantity of spring or flowing* water in a country; 

 2. It cannot yet be determined whether that diminution should be attrib- 

 uted to the less considerable quantity of rain which falls, or to a greater 

 evaporation of the pluvial supply, or to both causes united, or to some 

 new distribution of the water derived from rains; 3. The cultivation 

 j)racticed in an arid and denuded country dissipates a part of the flowing 

 waters; 1. In countries which have undergone no changes in cultivation 

 the quantity of water in streams or from sources appears to be always 

 the same; 5. Forests, while preserving such waters, economize and reg- 



