THE VAL DI CHIAITA. 515 



The bed of the Aruo near Arezzo and that of the Pagha at 

 the southern extremity of the Yal di Chiana did not differ much 

 in level. The general inclination of the valley was therefore 

 small ; it does not aj)pear to have ever been divided into oppo- 

 site slopes by a true watershed, and the position of the summit 

 seems to have shifted according to the varying amount and place 

 of deposit of the sediment brought down by the lateral streams 

 which emptied into it. The length of its principal channel of 

 drainage, and even the direction of its flow at any given point, 

 were therefore fluctuating. Hence, much difference of opinion 

 was entertained at different times with regai'd to the normal 

 course of this stream, and, consequently, to the question whether 

 it was to be regarded as properly an affluent of the Tiber or of 

 the Arno. 



The bed of the latter river at the bend has been eroded to the 

 depth of thirty or forty feet, and that, apparently, at no very re- 

 mote period.* If it were elevated to what was evidently its 

 original height, the current of the Arno would be so much above 

 that of the Pagha as to allow of a regular flow from its channel 

 to the latter stream, through the Yal di Chiana, provided the bed 

 of the valley had remained at the level which excavations prove 

 it to have had a few centuries ago, before it was raised by the 

 deposits I have mentioned. These facts, together with the testi- 

 mony of ancient geographers which scarcely admits of any other 

 explanation, are thought to prove that all the waters of the Up- 

 per Arno were originally discharged through the Yal di Chiana 

 into the Tiber, and that a part of them still continued to flow, at 



ancient observation of the fact just stated on the authority of Fossombroni. 

 Ignorance mistakes the effect for the cause, and the absence of this bird may 

 have been supposed to be the occasion, not the consequence, of the unhealthi- 

 ness of particular locab'ties. This opinion once adopted, the swallow would 

 become a sacred bird, and in process of time fables and legends would be in- 

 vented to give additional sanction to the prejudices which protected it. The 

 Romans considered the swallow as consecrated to the Penates, or household 

 gods, and according to Peretti {Le Berate del Villaggio, p. 168) the Lombard 

 peasantry think it a sin to kill them, because they are le galUnelle del Signore, 

 the chickens of the Lord. 



* Able geologists infer from recent investigations, that, although the Arno 

 flowed to the south within the pliocenic period, the direction of its course was- 

 changed at an earlier epoch than that supposed in the text. 



