ON THE IMPROVEMENT OF SOIL. 163 



moisture and air. Marl in masses would be totally use- 

 less on the ground ; yet it is necessary to begin by laying 

 it on the ground in heaps, for the more it is heaped the 

 more it dilates, splits, and crumbles to dust ; in which 

 state it is fit to spread upon the ground. 



Marl is sometimes intermixed with other earths ; some- 

 times formed into a compost with manure before it is laid 

 on the soil : it should be applied sparingly at a time, and 

 renewed frequently. Its advantages are manifest: it sub- 

 divides the soil and accelerates decomposition, its calca- 

 reous particles disorganizing all animal or vegetable bod- 

 ies, by resolving them into those simple elements in which 

 state they combine with oxygen ; it facilitates this union : 

 hence, though not itself of a nutritious nature, it promotes 

 the nourishment of plants by preparing their food. The 

 best period for marling ground is the autumn. 



Lime is also an excellent amendement. It is procured 

 from limestone by exposing it to the heat of the kiln, 

 which evaporates the water and carbonic acid with which 

 lime is always found combined in nature, and renders it 

 quick, as it is commonly called ; that is to say, of a caus- 

 tic burning nature, having such an avidity for water and 

 carbonic acid, from which it has been forcibly separated, 

 that it seizes upon these bodies wherever they are to be 

 met with, and disorganises the compounds in which they 

 are contained in order to combine with them. 



Emily. But since lime is of so destructive a nature, I 

 should have thought that it would have been necessary to 

 add, instead of subtracting, water and carbonic acid, in 

 order to soften its caustic properties, which seem calcu- 

 lated rather to destroy than promote vegetation. 



Mrs. B. Were quick-lime applied immediately to 

 plants, it is true that it would prove a poison to them ; 

 but, when spread upon the earth, it rapidly attracts water 

 and carbonic acid from the atmosphere, and it is only 

 when thus modified that it promotes vegetation. 



Emily. Then why force from it, in the kiln, those 

 very ingredients which must be restored to it so soon af- 

 terwards ? 



896. What is said of marl in masses'? 897. With what is it mix- 

 ed*? 898. How does it operate on the soill 899. How is lime 

 prepared, and how does it affect the soil 1 ? 900. If applied immedi- 

 ately to plants how would it affect them! 



