Burning Land for Manure. 



47 



a natural soil, composed of certain kinds of disintegrated lava, or 

 even granite, in which it is even e\4dent that an actual analvsis 

 would detect the presence of a lar^e per centage of alkali, not 

 improbably of a certain amount of phosphate of lime, and,, in 

 short, of all those ingredients which plants require for their 

 support in suflBcient abundance. Nevertheless land of this de- 

 scription, in consequence of the close union of the elementary 

 matters of which it consists and the compactness of its mechanical 

 texture, might he as barren and as incapable of imparting food to 

 plants, as an artificial soil composed of pounded glass is known 

 to be. notwithstanding the large propordon of alkali contained 

 in it." 



'■In order, therefore, to ascertain the respective amount of the 

 active and dormant ingredients existing in soils, the writer di- 

 gested some soil for four or five successive hours in muriatic 

 acid, justly observing that whatever cannot be extracted from a 

 soil by such a digestion must be in such a state of combination 

 as will render it totally incapable of imparting anything to a plant 

 for such a period of time, at least, as can enter economically into 

 the calculations of the agriculturist ; and moreover that all which 

 muriatic acid exiracts, but which water impregnated with carbonic 

 acid fails in dissolving, ought to be regarded as contributing 

 nothing towards present fertility, although it may ultimately be- 

 come available as food lor plants." 



Dr. Daubeny. therefore, first ascertained the nature and 

 amount of the ingredients separable from a given weight of soil 

 by means of muriatic acid : and secondly, those obtained from an 

 equal weight by a definite quantity of water impregnated with 

 carbonic acid gas. Thus bv a careful analysis he ascertained — 

 That the soil of the Botanic Garden at Oxford contained within 

 an area of 100 square feet and a depth of 3 feet from the surface 

 3-5 lbs. of phosphoric acid, 6-9 lbs. of potash, and 2-9 lbs. of 

 soda, all in a state to be separated from the general mass by 

 muriatic acid."' 



That the above, however, were for the most part in a dormant 

 condition, appeared from the much smaller amount of the same 

 which could be extracted by water containing carbonic acid ; for 

 it was found that of all the alkaline sulphates'^ not 11 lbs. could 

 be procured by these means instead of 19 '2 lbs. 



By operating in a similar manner upon soils of the same qua- 

 lity as the above, which had been exhausted by several years' 

 previous cropping, it appeared that the amount of the ingre- 

 dients alluded to as dormant in the soil did not much vary from 



* The alkalies were estimated as sulphates, as it was found convenient 

 to unite them with sulphuric acid, in vrhich state they admitted of being 

 heated and weighed without incurring loss. 



