330 M. BECQUEREL, ON THE CLIMATIC EFFECTS OF FORESTS. 



To complete the documents proper for elucidating the question, we 

 will add still other important observations. M. Berghaus^ found that 

 the volumes of water in the Oder and the Eble had diminished between 

 1778 and 1835 in the former, and between 1828 and 1838 in the latter, and 

 that this decrease still continued, and, remaining so, it was at length ne- 

 cessary to change the form of the boats ; and statistics show that it can 

 only be ascribed to the clearing of mountains. 



Attempts have been made to ascertain whether the amount of water 

 falling in different countries in Europe have diminished, but without 

 finding proofs. In fact, since 1G89, it has been observed that the amount 

 of water falling at Paris slightly increased, rather than diminished 

 Cesaris has noticed the same at Milan, since 17G3, and it is the same at 

 Eochelle and in the valley of the Rhone. 



The hypothesis of the diminution of rains must not be rejected until 

 we consider whether the number of rain-falls has changed, and take into 

 account the fact generally admitted that great rains furnish more water 

 to the rivers than the same amount of water falling through several 

 days, with intervals of dryness between. But the discussion of obser- 

 vations still does not clear up the question, and we must still appeal to 

 the changes wrought upon climate by cultivation. 



It may possibly happen that earthquakes may disturb a spring by 

 moving the strata, but this is rare. A great number of facts, on the 

 contrary, tend to show that the diminution of volume is found almost 

 immediately following upon great clearings. We may cite especially 

 the example of the waters of Marmato, already noticed. 



Other examples may be mentioned that are not without interest. The 

 Romans were able to bring to Oileaus the waters of the fountain of 

 l'Etuv6e, which is now entirely dry.^ Important excavations, under- 

 taken some years since, have brought to light the foundations of Roman 

 structures for supplying water where spring no longer exists, and a 

 stream which empties into the Loire east of Orleans, and contributed 

 in the siege of 1428, and to the turningof mills, no longer exists as it did 

 when Orleans had great forests on that side, now cleared. By reason 

 of this clearing the wells in the city give less water than formerly, so 

 that the municipal authorities have been obliged in recent years to 

 bring waters for domestic use from the sources of the Loiret, at a cost 

 of 300,000 francs. 



In the canton of Chatillon-sur-Loing (Loiret) there is a cofaimune 

 named Sainte Genevieve-des-Bois, which was once wooded, but now 

 there exists only some li ttle clumps of trees here and there. A stream 

 flowed by the village which is now a dry channel, except when filled in 

 winter. 



^Cou7'8 ffAfjricullure, By M. Gasp.irin, ii, 146. 



2 Au analogous instance is presented in Patroon's Creek, that some thirty yenrs ago 

 vras taken and the mill privileges purchased for a hirge sum by the city of Albany, 

 N. Y., for supplying that city with pure water. This stream had been perennial, and 

 its ample supply mainly derived from the drainage of a flat, sandy country, with few 

 springs, but an abundance of water in the soil so long as it remained covered with 

 forest vegotatiou. This growth having largely disappeared, the stream has failed, and 

 now its diminished supply is made up by pumping from the Hudson River. 



An instance of conservative hydrology of dillerent results is presented on the oppo- 

 site side of the river and but a few miles distant. Two streams that flow into the Hud 

 son, iu the city of Ti'oy (the Poestenkill and Wynantskill), have an ample amount of 

 hydraulic power maiutaiued through the summer by the construction of reservoirs in 

 the hilly country arouud their sources, for retaining the excess of winter rains for 

 discharge at the time when needed throughout the summer. Although the forests 

 Lave no direct connection with the water-supply in the latter case, there can be no 

 doubt but that their presence would contribute greatly to the cost of maiutenance by 

 easing the violence of floods and securing the more unirorm delivery of the waters. 

 (H.) 



