Improvement of Land by Silting 



263 



and in the district of the mouths of the Rhone, 

 between Aries and Mirimas, for example, on broad, 

 flat plains of extremely coarse gravel, where in earlier 

 years the uncontrolled waters have permitted no soil 

 to form, this system of silting, "colmatage" or 



Fig. 48. Head-gate on the Durance above Avignon, France. 



" warping, " has been introduced, and rich deposits 

 laid down among and above the coarse materials, 

 until productive fields, orchards and gardens have 

 taken the place of wide reaches of naked gravel 

 beds. 



Fig. 48 is a head - gate on the Durance, above 

 Avignon, where a portion of the water of the district 

 is taken out. The soil here, for depths exceeding 

 10 feet, as shown by cuts observed, is made up, seem- 



