518 THE VAL DI CHIANA. 



not meet with immediate general acceptance, but it was soon 

 adopted for local purposes at some points in the southern part oi 

 the valley, and it gradually grew in public favor and was extend- 

 ed in appKcation 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 Rome — the boundary be- 

 tween which states crossed the Yal di Cliiana not far from the 

 half-way point between the two rivers — and of reconciling other 

 conflicting interests, prevented the resumption of the projects 

 for the general drainage of the valley until after the middle of 

 the eighteenth century. In the meantime the science of hy- 

 drauhcs 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 dimin- 

 ished 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 tm^n 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 suc- 

 cess has fully justified the expectations of the most sanguine ad- 

 vocates of the scheme. The plan of improvement embraced two 

 branches : the one, the removal of obstructions in the bed of the 

 Arno, and, consequently, the further depression of the channel 

 of that river, in certain places, with the view of increasing the 

 rapidity of its current ; the other, the gradual filling up of the 

 ponds and swamps, and raising of the lower grounds of the Yal 

 di Chiana, by directing to convenient points the flow of the 

 streams which pour down into it, and there confining their 

 waters by temporary dams until the sediment was deposited where 

 it was needed. The economical result of these operations has 

 l3een, that in 1835 an area of more than four hundred and fifty 



