BASINS OF EECEPTION. 477 



enough to retain tlie superfluous waters of great rains and thaws.* 

 Besides the utility of such basins in preventing floods, the con- 

 struction of them is recommended by very strong considerations, 

 such as the furnishing of a constant supply of water for agricul- 

 tural and mechanical purposes, and, also, their value as ponds for 

 breeding and rearing fish, and, perhaps, for cultivating aquatic 

 vegetables.f 



The objections to the general adoption of the system of reser- 

 voii's are these : the expense of their construction and main- 

 tenance ; the reduction of cultivable area by the amount of sur- 

 face "they must cover; the interruption they would occasion to 

 free communication ; the probability that they would soon be 

 filled up with sediment, and the obvious fact that when full of 

 earth, or even water, they would no longer serve their principal 

 purpose ; the great danger to which they would expose the coun- 

 try below them in case of the burstuig of their barriers ; ^ the 

 evil consequences they would occasion by prolonging the flow of 

 inundations in proportion as they diminished their height ; the 

 injurious effects it is supposed they would produce upon the 

 salubrity of the neighboring districts ; and, lastly, the alleged im- 

 possibihty of constructing artificial basins sufficient in capacity 

 to prevent, or in any considerable measure to mitigate, the evils 

 they are intended to guard against. 



The last argument is more easily reduced to a numerical ques- 

 tion than the others. The mean and extreme annual precipita- 

 tion of all the basins where the construction of such works would 



* On the construction of temporary and more permanent barriers to the cur- 

 rents of torrents and rivulets, see Marchand, Les Torrents des Alpea, in Bevtia 

 des Eaux et Forets for October and November, 1871. 



f In reference to the utilization of artificial as well as natural reservoirs, sec 

 AcKERHOP, Die Nutzung der Teiche und Oewdsser, Quedlinburg, 1869. 



X For accounts of damage from the bursting of reservoirs, see Vallee, 

 Memoire sur les Reservoirs d' Alimentation des Canaux, Annates des Fonts et 

 Chaussees, 1833, ler semestre, p. 261. 



The dam of the reservoir of Puentes in Spain, which was one hundred and 

 sixty feet high, after having discharged its functions for eleven years, burst, 

 in 1802, in consequence of a defect in its foundations, and the eruption of the 

 •water destroyed or seriously injured eight hundred houses, and produced 

 damage to the amount of more than a million dollars. — Aymakd, Irrigations 

 du Midi de V Europe, pp. 257-259. 



