THE VAL DI CHIANA. 5385 
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 deter- 
mined in either direction, and the opposite descents of the val- 
ley made to culminate at the north or at the south end of the 
Jevel. 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. 
Various schemes were suggested at this time for drawing 
off the stagnant waters, as well as for the future regular drain- 
age of the valley, and small operations for those purposes were 
undertaken with partial success; but it was feared that the 
discharge of the accumulated waters into the Tiber would pro- 
duce a dangerous inundation, while the diversion of the drain- 
age 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 pre- 
served, proposed, as the only possible method of improvement, 
the piercing of a tunnel through the hills bounding the valley 
on the west to convey its waters to the Ombrone, but the ex- 
pense and other objections 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 embank- 
ments across the portion of the valley lying within 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 neighborhood. 
The effect of this measure and of the continued spontaneous 
* Morozzi, Dello stato del? Arno, ii., pp. 39, 40. 
