On Manures. 225 



of lime or clay (H 9 ). It may likewise be of use in opening 

 the pores of an adhesive clay soil ; but it cannot unmixed be 

 considered as an enriching manure, though it may be ad- 

 vantageously employed in composts. It has been remarked, 

 that no plants grow on the refuse of a peat-stack or heap, 

 which could not be the case, if that species of earth, by it- 

 self, were favourable to vegetation. 



3. Clay, or Sand. The plan of improving the texture of 

 a soil, by conveying clay, where sand predominates, and the 

 reverse, has been already alluded to, in Chap. I. Sect. 2, 

 and has been attended with great advantage. Clay can 

 hardly fail to be useful to sand ; but it has been justly ob- 

 served, that many soils acquire the name of clays, because 

 they are cohesive for want of effective draining, which, when 

 examined, are found to be sandy loams, and consequently 

 have no occasion for any additional quantity of sand( 34 ). 

 In Cheshire, sand is frequently used as manure on stiff lands, 

 and when laid on in sufficient quantities, with great suc- 

 cess (** 1 ). 



4. Burnt Clay It is well known, that burning clay is an 



old practice, which, at various periods, has been pursued with 

 energy, and at other times has fallen into neglect. In a work 

 printed in London, an. 1732, " The Country Gentleman's Com- 

 " panion" it is stated, that the Earl of Halifax was the inven- 

 tor of that useful mode of improvement ; and that it was much 

 practised in Sussex. There are, in that work, engravings of two 

 kilns for burning clay, one adopted in England, and the other 

 in Scotland, where it is said to have been ascertained, that 

 lands, reduced by tillage to poverty, would produce an excel- 

 lent crop of turnips, if the ground were ploughed two or three 

 times, and clay ashes spread over it. In 1786, Mr James 

 Arbtithnot, of Peterhead, revived the practice, and tried seve- 

 ral successful experiments with burning clay, with a view, both 

 to simplify the process, and to reduce the expense ; but it has 

 never been very extensively adopted ( a43 ). An intelligent 

 correspondent, however, maintains, that burnt clay deserves 

 to be ranked among the most valuable manures, not only from 

 the facility with which it is obtained, but from its being suited 

 to soils in general, and to crops of every description ( Z43 ). 

 This is accounted for, by its containing oxide of iron, which 

 is favourable to vegetation. It is said, that more than one 

 half of the potatoes raised in Ireland, more especially in the 

 western parts of that country, are produced from that ma- 

 nure (*44). 



In preparing clay for manure, a great distinction ought to 



p 



