THE VAL DI CniANA. 517 



valley Ijiiig witliin its territory, and these obstructions, though 

 not specifically intended for that purpose, naturally promoted the 

 deposit of sediment and the elevation of the bed of the valley in 

 their neisrhborhood. The effect of this measure and of the con- 

 tinned spontaneous action of the torrents was, that the northern 

 slope, which in 1551 had commenced at the distance of ten miles 

 from the Arno, was found in 1605 to begin nearly thu-ty miles 

 south of that river, and in 1645 it had been removed about six 

 miles farther in the same direction.* 



In the seventeenth century the Tuscan and Papal Governments 

 consulted Galileo, Torricelh, Castelli, Cassini, Yiviani, and other 

 distinguished philosophers and engineers, on the possibihty of re- 

 claiming the valley by a regular artificial drainage. Most of these 

 eminent physicists were of opinion that the measure was imprac- 

 ticable, though not altogether for the same reasons ; but they seem 

 to have agreed in thinking that the opening of such channels, in 

 either direction, as would give the current a flow sufliciently 

 rapid to drain the lands properly, would dangerously augment 

 the inundations of the river — whether the Tiber or the Arno — • 

 into which the waters should be turned. The general improve- 

 ment of the valley was now for a long time abandoned, and the 

 waters were allowed to spread and stagnate until carried off by 

 partial drainage, infiltration and evaporation. Torricelli had 

 contended that the slope of a large part of the valley was too 

 small to allow it to be drained by ordinary methods, and that no 

 practicable depth and width of canal would suffice for that pur- 

 pose. It could be laid dry, he thought, only by converting its 

 surface into an inclined plane, and he suggested that this might 

 be accomphshed by controlling the flow of the numerous torrents 

 which pour into it, so as to force them to deposit their sediment 

 at the pleasure of the engineer, and, consequently, to elevate the 

 level of the ai-ea over which it should be spread.f This plan did 



* MoROzzi, Dello state, etc., delV Arno, ii., pp. 39, 40. 



f Torricelli thus expressed himself on this point : " If we content ourselves 

 with what nature has made practicable to human industry, we shall endeavor 

 to control, as far as possible, the outlets of these streams, which, by raising 

 the bed of the valley with their deposits, will realize the fable of the Tagus 

 and the Pactolus, and truly roU golden sands for him that is wise enough to 

 avaa hi m self of them." — Fossombroni, Memorie sopra la Val di Chiana, ix 

 219. 



