422 
THE YAL DI CHIAJSfA. 
did not meet with immediate general acceptance, but it was 
soon adopted for local purposes at some points in the southern 
part of the valley, and it gradually grew in public favor and 
was extended in application until its final triumph a hundred 
years later. 
In spite of these encouraging successes, however, the fear 
of danger to the valley of the Arno and the Tiber, and the 
difficulty of an agreement between Tuscany and Home—the 
boundary between which states crossed the Yal di Chiana not 
far from the halfway point between the two rivers—and of 
reconciling other conflicting interests, prevented the resump¬ 
tion of the projects for the general drainage of the valley until 
after the middle of the eighteenth century. In the mean time 
the science of hydraulics had become better understood, and 
the establishment of the natural law according to which the 
velocity of a current of water, and of course the proportional 
quantity discharged by it in a given time, are increased by 
increasing its mass, had diminished if not dissipated the fear 
of exposing the banks of the Arno to greater danger from 
inundations by draining the Yal di Chiana into it. 
The suggestion of Torricelli was finally adopted as the basis 
of a comprehensive system of improvement, and it was decided 
to continue and extend the inversion of the original flow of the 
waters, and to turn them into the Arno from a point as far to 
the south as should be found practicable. The conduct of the 
works was committed to a succession of able engineers who, 
for a long series of years, were under the general direction of 
the celebrated philosopher and statesman Fossombroni, and the 
success has fully justified the expectations of the most sanguine 
advocates of the scheme. The plan of improvement embraced 
two branches : the one, the removal of certain obstructions in 
the bed of the Arno, and, consequently, the further depression 
of the channel of that river, in certain places, with the view 
by raising the bed of the valley with their deposits, will realize the fable 
of the Tagus and the Pactolus, and truly roll golden sands for him that is 
wise enough to avail himself of them.”— Fossombroni, Memorie sopra la 
Val di Chiana , p. 210. 
