MANUEKS. 157 



mixed with farmyard manure, vegetable mould, &c., and is one of 

 the constituents of surkhi-ash (No. 7). 



6. CHARCOAL. This, like wood-ash, can only constitute an 

 auxiliary manure. Its high manurial value is almost entirely due 

 to the remarkable avidity with which it absorbs ammonia, carbonic 

 acid and other gases, and the equal facility with which it gives 

 them up to the roots of plants, and to its rendering stiff and cold 

 soils friable and warm, and dry and porous soils hygroscopic. 



7. SURKHI-ASH. As the name imports, this substance is a mix- 

 ture of burnt earth and a large proportion of vegetable ash and 

 charcoal dust. The ordinary mixed ash and dust of a brick, tile 

 or charcoal kiln may be used ; but, whenever possible, the manure 

 should be specially prepared. On land covered with rich herbage 

 the surface soil, with the roots of grasses and other plants that 

 traverse it, should be cut up, while still moist, in brick-shaped soda 

 (Fig. 10), which should be dried in the sun. The best soil for the 

 purpose is loam, the poorest are sandy soils. Stiff clays, especially 

 if they are ferruginous, are easily liable to be burnt too hard, 

 AVhen the sods are dry, they should be piled up in small kilns 

 about 1^ yards in diameter and 3 feet high, and the kilns should 

 then be fired in dry weather. The arrangement of the kilns is 

 shewn in Fig 11. a is a mass of small wood over which two layers 

 of the sods are built up in the form of a dome b. Over this is 

 laid a layer of small wood c, and over this again two layers of sods 

 ?, and so on. In building up the kiln a passage m.m. is left on a 

 level with the ground, whereby the kiln is fired. Obviously tho 

 sods should be arranged with their upper grassy surface inside. 

 As the combustion progresses and the small wood gets consumed > 

 the entire mass subsides, producing vents here and there which 

 should be at once filled up and covered over with fresh sods. In 

 doing this more sods are often used up than in the first building 

 up of the kiln. The completion of the burning may require seve- 

 ral days. When the kiln has cooled down sufficiently to be 

 handled, the sods should be taken out and broken up fine, an oper- 

 ation that is more easily effected before they have become quite 

 cold. The surkhi-ash should be at once collected in heaps and 

 put under shelter. The advantages of using surkhi-ash are two- 

 fold. Besides increasing the consistency of a too free, and dimi- 

 nishing the compactness of a too stiff, soil, it renders immediately 

 available to the roots of plants, in a soluble form, the mineral mat- 

 ters present both in the small wood, leaves, roots and other vege- 

 table refuse burnt and in the soil itself of the sods ; but its 



