SUBMERSION OF VINEYARDS. 203 



^correspond to the systems of plantation in use. On hori- 

 zontal lands where large beds can be made it is preferable 

 to give them a square shape, as a greater area can be sur- 

 rounded with the same length of bank, and as it allows cross 

 ploughing. If the land is slightly sloped it is necessary to 

 make rectangular beds following the mean line of profile, so 

 as not to increase the height of the lowest bank. 



(B.) . Size of beds. From the point of view of the destruc- 

 tion of phylloxera the larger the bed the better. As a 

 matter of fact the area of the banks is small if compared to 

 the whole surface, and we know that the roots of vines 

 growing under the banks always harbour living insects and 

 become a centre of infection, which must be diminished as 

 much as possible. 



But is it generally impossible in practice to apply this 

 principle to its last limit, which would be that of making 

 a single bed of the whole vineyard, surrounding it by a 

 single bank. The reasons preventing it are 1st, that the 

 soils are not horizontal, thus compelling the slope to be 

 divided in sections to avoid making too high a bank on the 

 lowest side ; 2nd, the impossibility of having a sufficient 

 quantity of water to fill it ; 3rd, the danger of having the 

 banks washed away by the small waves formed by the wind 

 if the surface is too large ; 4th, the large loss which would 

 result from the bank breaking in one point and emptying 

 the whole basin. To sum up, the size which seems to be the 

 most practical is from 7 to 25 acres. 



The beds should be arranged so as to allow the water to 

 overflow from the top into the lower basins ; for that purpose 

 small sluice boxes are placed in suitable positions, these 

 being also fed from the main channel and emptying auto- 

 matically. Finally, drains must be established to enable 

 the soil to be drained quickly after the operation. 



(C.) Banks. The banks should be prism-shaped, with 

 slopes at 45. This shape insures greater strength, and 

 enables them to be used as paths during the operation. The 

 width on the top depends on the depth of the water. It 

 varies between 18 inches for a height of 18 inches, which is 

 the minimum, and 3 feet for a height of 18 inches to 3 feet. 

 If very large beds are made the banks should be large enough 

 to enable them to be used as roads during the vintage. There 

 is no danger in making banks as high as 3 feet, but above 



