516 THE VAL DI CHIAISTA. 



least occasionally, in that direction down to the days of the E-o- 

 man empire, and perhaps for some time later. The depression 

 of the bed of the Arno, and the raising of that of the valley by 

 the deposits of the lateral torrents, finally cut off the branch of 

 the river which had flowed to the Tiber, and all its waters were 

 turned into its present channel, though the drainage of the prin- 

 cipal part of the Yal di Chiana appears to have been in a south- 

 eastwardly direction until within a comparatively recent period. 



In the sixteenth century the elevation of the bed of the valley 

 had become so considerable, that in 1551, at a point about ten 

 miles south of the Arno, it was found to be not less than one 

 hundred and thirty feet above that river ; then followed a level of 

 ten miles, and then a continuous descent to the Paglia. Along 

 the level portion of the valley was a boatable channel, and lakes, 

 sometimes a mile or even two miles in breadth, had formed at 

 various points farther south. At this period the drainage of the 

 summit level might easily have been determined in either direc- 

 tion, and the opposite ascents of the valley made to culminate at 

 the north or at the south end of the level. In the former case, 

 the watershed would have been ten miles south of the Arno ; in 

 the latter, twenty miles, and the division of the valley into two 

 opposite slopes would have been not very unequal. 



Yarious schemes were suggested at this time for drawing off 

 the stagnant waters, as well as for the future regular drainage of 

 the valley, and small operations for those purposes were under- 

 taken with partial success ; but it was feared that the discharge 

 of the accumulated waters into the Tiber would produce a 

 dangerous inundation, while the diversion of the drainage into 

 the Arno would increase the violence of the floods to which that 

 river was very subject, and no decisive steps were taken. In 

 1606 an engineer, whose name has not been preserved, proposed, 

 as the only possible method of improvement, the piercing of a 

 tunnel through the hills bounding the vaUey on the west to con- 

 vey its waters to the Ombrone, but the expense and other objec- 

 tions prevented the adoption of this scheme.* The fears of the 

 Roman Government for the safety of the basin of the Tiber had 

 induced it to construct embankments across the portion of the 



* MoKOZzi, Dello siato, etc., delV Arno, ii., pp. 39, 40. 



