WITH A VIEW TO HORTICULTURE. 53 



then in seven years the black matter or mould remaining of the dung will he 

 found among the roots of the grass at the surface, the sand in a stratum 

 three or four inches below the surface, and the lime at the bottom of the 

 artificial soil. By placing the same mixture in a flower -pot, and watering it 

 frequently during a year, the pot being plunged in the soil, the same result 

 will take place sooner, and be more conspicuous. If the pot be kept con- 

 stantly immersed in water to within an inch of the brim, the result will 

 take place in the course of a few days. These facts ought to be kept con- 

 stantly in mind by whoever w T ould improve soils by admixture ; if they are 

 not, disappointment is very likely to ensue. When soils mixed together are 

 comparatively without organic matter, and when the particles of which they 

 are composed are very small, the mixture becomes more intimate ; the 

 particles of the one soil filling up the interstices among the particles of the 

 other, and the amalgamation as it may be termed is then so complete that 

 the earths will never afterwards separate. In this way pure sands may be 

 improved by the admixture of pure clays, or by marls or chalks. The 

 words pure and amalgamate are here used, not in a chemical, but in a 

 popular sense. 



173. Changing the inclination of the surface of soils is a mode of improve- 

 ment that may frequently be adopted on a small scale, by arranging a 

 steep slope into narrow terraces, and a broad slope into level platforms. The 

 former mode has been practised from time immemorial in the Land of 

 Canaan, and in other countries of the East, and the latter is common in 

 France and Italy, in order to admit of surface irrigation without waste of 

 water. By this last mode, a field or garden is arranged into different plat- 

 forms, which may either be on the same or on different levels. In the former 

 case, the water is let into one platform after another ; or, if there is an abun- 

 dant supply, into several at the same time ; in the latter case the supply of 

 water is conducted to the highest platform, which is first watered, and 

 the others follow in the order of their elevation. Arrangements of this kind 

 are not so important in British gardens as they are in those of warmer 

 climates ; but still they might in many cases be advantageously introduced 

 with a view to watering summer crops. 



174. Burning of soils has been resorted to as a means of altering their 

 texture, destroying injurious substances, and changing or forming others 

 which may act as a manure. Burning is useless on siliceous sands contain- 

 ing little or no vegetable matter ; but on all soils containing chalk, lime, or 

 clay, it may be practised with advantage. By burning calcareous or chalky 

 soils, the same effect is produced as if quicklime had been procured and 

 added to the soil ; and by burning clayey soils the same result is obtained as 

 if sand had been procured and mixed with them. The effect of burning clay 

 is totally different from that of burning sand or lime. On sands and gravels 

 burning can have no effect, except that in some cases it renders the particles 

 smaller. Burning lime drives off the carbonic acid and the water, and renders 

 the lime caustic and well adapted for decomposing organic matter ; but the 

 lime has no sooner lost its water than it begins to attract it again, and after a 

 certain period will be found in the same state of combination with water and 

 carbonic acid as it was before. Clay, on the other hand, when once the water 

 is driven off by burning, will never regain it, but remains for ever after- 

 wards in a state which, with reference to its mechanical effect on a soil, is 

 exactly the same as that of sand. This is a fact, the great importance of 



