ON MANURES. 79 



sand which is within reach of the tide, being- thrown upon the 

 sliore in storms, is, in some places, carted oft", and laid upon the 

 land with considerable advantage, though in other parts the 

 practice seems utterly unknown. Being finely attenuated, it 

 blends intimately with the soil, and thus produces very sensi- 

 ble effects in the correction of cold clays and cohesive loams, 

 on which it is usually laid to the amount of about twenty tons 

 per acre. Its chief value will, however, be proportioned to the 

 quantity of calcareous matter, or of shells, which it contains, and 

 this is in some places found to be so large as nearly to equal 

 the common properties of lime. 



It is also found in strata, imbedded in sand-cliffs, at the 

 height sometimes of 40 or 50 feet above the level of the sea, 

 in which places it is generally denominated crag, and was, no 

 doubt, deposited in former ages, ere the water had receded 

 from the shore. 



Lime — Is applied to a great variety of uses : it is employed 

 in medicine as an antacid ; mortar is composed of it, when 

 combined with sand ; and it serves as a manure, which is the 

 only view in which we now have to regard it. When used 

 for the purposes of agriculture, it is formed by exposing the 

 substances we have mentioned to a certain degree of heat in 

 the furnace, or kiln, of the lime-burner. When this has been 

 continued for a sufficient length of time, their weight becomes 

 considerably diminished, though they retain their former shape 

 and bulk ; and either limestone or chalk, when thus reduced, 

 is in most places known by the name either of lime-shells, or 

 shell-lime, or simply shells. In this state it is called quick- 

 lime: the materials of which it is thus composed possess hardly 

 any active property, but when burned, it then becomes caustic 

 to the tongue, and effects the speedy decomposition of most 

 vegetable and animal bodies. When applied in this form — 

 either in the way of compost, or spread over the soil by itself — 

 it is so far from affording nutriment to any thing that may be 

 there growing, that, were its efffects to be long continued, it 

 would consume it. But if water be thrown upon it, a great 

 degree of heat is in a short time generated ; the burnt shells 

 begin to crack and burst asunder, and the mass gradually 

 crumbles down, or falls, as it is more commonly said, into a 

 fine powder, which becomes white, of whatever colour it may 

 have been before it was calcined. Or when it has been 

 exposed for a short time to the influence of the atmosphere, it 

 is also found to lose this caustic power, and it is thus recon- 

 H 



