'274 VEGETABLE FOOD. 



the slug. Both lime and chalk are excellent appli- 

 cations on clayey soil for counteracting its adhesive- 

 ness ; because, as both are powerful absorbents of 

 water, the frost acts with redoubled force in disrupting 

 the compact surface of the clay rendering ploughing 

 and harrowing easy. Both these substances, as well 

 as common salt, are also used on dry gravelly land ; 

 they being attractive of moisture in all seasons, and 

 consequently highly serviceable to summer crops. It 

 is only when lime is in its caustic state it is preju- 

 dicial to slugs ; after being slaked and saturated with 

 moisture it only acts in the manner of chalk. Some 

 kinds of lime-stone contain magnesia; which last 

 substance has been found deleterious to vegetation 

 in its caustic state : and therefore only fit to be 

 used on peaty soils. 



All fresh or newly broken up ground contains 

 some peculiar quality particularly acceptable to plants, 

 especially such as have never, or not for a long period 

 before, been cultivated thereon. Such soil is called 

 maiden or untried ; and unless decidedly sterile, by 

 reason of wanting a sufficient depth of surface mould, 

 or strongly impregnated with metallic principles, 

 will yield abundant crops successively for several 

 years. From this circumstance it would appear not 

 only that vegetable food exists in soils which have 

 never been enriched by the cultivator, but that it is 

 also exhaustible. Hence the necessity of applying 

 manure to keep land in heart, and to enable it to 

 yield remunerating crops. 



