PREPARATION OF THE SOIL. 51 



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

 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 Fah. 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 j 

 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 



