PREPARATION OF THE SOIL. 51 



the attacks of disease and insects. The grapes, too, 

 will not ripen well, but will remain sour and ill-fla- 

 vored. 



M. Gasparin gives the following observations with 

 regard to the influence which a dry or a moist soil 

 exerts upon the grape : " Other things being equal, 

 we obtain grapes which contain much sugar and lit- 

 tle acid from vines grown in a dry soil ; more free 

 acid in a moist soil, and much acid, albumen and 

 mucilage with little sugar in a soil which is absolu- 

 tely wet." 



Another advantage consists in, the fact that well- 

 drained land always possesses a higher temperature 

 than that which is wet. This difference amounts to 

 10° to 12° Fall, and is accounted for by the rapid 

 absorption of heat by the water as it becomes con- 

 verted into vapor. During this process, too, it is pro- 

 bable that the nascent vapor robs the earth of a por- 

 tion of the ammonia and gases which it would have 

 separated from the water and retained if it had acted 

 as a filter and the water had passed off by the drains. 

 But however this may be, its effect on temperature 

 is such that Johnson regards thorough draining as 

 equal to a change of climate. 



But not only does draining enable the soil to filter 

 all the -water which descends upon it, retaining its 

 ammonia, gases and even salts ; it is probable that by 



