OF WATERING PLANTS. 147 



certain elevation, found an issue to the north, precisely 

 in the opposite direction to that in which the water for- 

 merly flowed out of the valley. The rivulets, therefore, 

 on entering the valley, were all obliged to change their 

 course. In making this turn, their velocity was dimin- 

 ished ; and having no longer power sufficient to carry 

 with them the earthy materials with which they were la- 

 den, these were deposited in the lake, in which they ac- 

 cumulated, and, in the course of time, converted it into 

 a marsh. The ingenious and sagacious Torrecelli avail- 

 ed himself of the evil to devise a remedy ; and employed 

 the very means which had converted the lake into a 

 marsh to convert the marsh into dry land. 



Emily. That was a most happy idea ; but how did he 

 accomplish it ? 



Mrs. B. He caused a mound or bank of earth to be 

 raised towards the base of the hill, around the part where 

 a rivulet changed its course. This was left open on the 

 most elevated side ; so that the water, laden with earth, 

 in its descent might have free access to it ; on the lower 

 side a small aperture was made through which the water 

 alone could escape, leaving behind the earthy matter, 

 with which it was saturated. In the course of time, the 

 soil within this enclosure, was elevated by the accumula- 

 tion of earth, above the level of the stagnant water; and 

 rose, like a dry little island, on the edge of the marsh. 

 A contiguous enclosure was then made, and raised by 

 similar means ; a third and a fourth followed in succes- 

 sion. These labors have been going on during two 

 centuries : of late years they have been prosecuted with 

 great activity and sagacity by the celebrated Fosombroni 

 of Florence ; and only a few years more will be required 

 to complete them. Already you have beheld this district 

 transformed, from a melancholy and pestilential marsh, 

 into a richly cultivated valley, watered by a clear stream, 

 the result of the torrents purified from their earthy deposits. 



Caroline. It is, indeed, quite a metamorphosis; and 

 is not this mode adopted in other countries ? 



Mrs. B. It is frequently employed in the environs of 

 Bologna, and in several other parts of Italy. This ope- 



815. Why was the mud deposited instead of being carried away with 

 the water! 816 What was the plan of Torreeelli! 817. How 

 long have these labors been in operation'? 818. What is the present 

 condition of this valley! 819. Where else has this mode of operation 

 been adopted! 



