270 Horticultural Chemistry. 



bourhood. A soil with a just proportion of decomposing 

 matter, which insures that it will be capable of absorbing 

 moisture during the droughts of summer from the atmosphere, 

 as the most fertile soils are always the most absorbent, yet it 

 must not be too retentive of moisture, which is the case in such 

 soils as contain too much alumina ; neither must it too easily 

 part with it, which is a characteristic of those which contain 

 an excess of silica. A subsoil of gravel mixed with clay is 

 the best, if not abounding in oxide of iron : for clay alone retains 

 the moisture on the arable surface in too great an excess ; 

 and sand on the contrary carries it away too rapidly. It is, 

 however, evident that to insure these desiderata in any soil, 

 at all seasons, is impossible ; and it is as manifest that a soil 

 that would do so in one climate would fail in another, if the 

 mean annual temperature of them should differ, as well as 

 the amount in inches of rain which falls during the same 

 period. Since, in the western parts of England, more than 

 twice as much rain occurs as in the most eastern counties, or in 

 the proportion of 42 to 19, a soil in the east of England, for 

 any given crop, may be richer and more tenacious than the 

 one required for it on the western coast. Alumina, or clay, 

 imparts tenacity to a soil when applied ; silica, or sand, dimi- 

 nishes that power ; whilst chalk and lime have an interme- 

 diate effect, they render heavy soils more friable, light soils 

 more retentive. These simple facts are important ; two neigh- 

 bouring fields, by ah interchange of soils, being often rendered 

 fertile, which, before, were in the extremes of tenacity and 

 porosity. From these statements it is evident that no univer- 

 sal standard, or recipe, can be given for the formation of a 

 fertile soil, but one whose constituents approach in their pro- 

 portions to those of the following one cannot be unproductive 

 in any climate. It is a rich alluvial soil, which Mr. Sinclair, 

 in his invaluable Hortus Gramineus Woburnensis, gives as being 

 the most fertile for the grasses. 



■" Fine sand, 115; aluminous stones, 70; carbonate of 

 lime, 23 ; decomposing animal and vegetable matter, 34? ; 

 silica, 100; alumina, 28; oxide of iron, 13; sulphate of 

 lime, 2; soluble vegetable and saline matter, 7; loss, 8. 

 Total, 400." 



I have already stated what chiefly constitutes a fertile soil ; 

 it may be added that, to constitute one eminently such, its 

 earthy particles must be in a minute state of division, the more 

 so the more fertile will it be. In the above analysis 185 parts 

 only were separable by sifting through a fine searce, 215 parts 

 were impalpable; whereas poorer soils will often have 300 



