272 



CULINARY OR KITCHEN GARDEN. 



trace to about 1^ per cent. It assists in giving 

 the black colour to soil." 



These four substances constitute by far the 

 greatest bulk of every soil, except the chalky 

 and peaty varieties, but nevertheless, chemically 

 speaking, they are of trifling importance to plants, 

 whereas the remaining eight are so absolutely 

 essential that no soil can be cultivated with any 

 success, unless provided with them, either na- 

 turally or artificially. And yet, when it is con- 

 sidered that scarcely any of them constitute 1 

 per cent of the soil, their value will no doubt 

 excite surprise. The sole cause of their utility 

 lies in the fact that they constitute the ashes of 

 the plants ; and as no plant can by possibility 

 thrive without its inorganic constituents (its 

 ashes), hence no soil can be fertile which does 

 not contain the ingredients of which these are 

 made up. The very small per-centage of these 

 ingredients in any soil necessitates a minute 

 analysis of every soil before it can be ascertained 

 whether or not it contains any or what propor- 



tion of these ingredients. But the reason for 

 such minuteness in analysis becomes obvious 

 when we consider the immense weights which 

 have to be dealt with in practical agriculture ; 

 for example, every imperial acre of soil, consi- 

 dered as only 8 inches deep, will weigh 1884 

 tons, so that 0.002 per cent — that is, only a two- 

 thousandth per cent, the amount of sulphuric 

 acid in a barren soil — amounts to 80.64 lb. in 

 the imperial acre ! 



u Potash and soda exist in variable quantities 

 in many of the more abundant minerals, and 

 hence it follows that their proportion in soil 

 will vary according to the mineral which pro- 

 duced it. For the sake of reference, I have 

 subjoined the following table, which shows the 

 amount per cent of alkalies in some of these 

 minerals, and likewise a rough calculation of 

 the whole amount per imperial acre, on the 

 supposition of a soil composed solely of these 

 rocks, and of a depth of 10 inches, and the 

 amount is abundant beyond conjecture. 



Name of 

 Mineral. 



Amount per 

 cent of Alkali. 



Name of Alkali. 



Amount per imperial acre in a soil 

 10 inches deep. 



Felspar, 

 Clinkstone, . 

 Ciayslate, 

 Basalt, 



17.75 

 3.31 to 6.62 

 2.75 to 3.31 

 5.75 to 10. 



Potash, 



Potash'and soda. 

 Potash", 



Potash and soda, 



tons cwt qrs lb tons cwt qrs lb 



422 18 2 8 — 



71 17 2 0 to 143 15 0 0 

 35 18 3 0 to 71 17 2 0 

 17 0 0 0 to 25 7 3 7 



" One unacquainted with chemistry will na- 

 turally ask the question — How is it that these 

 alkalies have not been long ago washed away by 

 the rain, since they are both so very soluble in 

 water ? The reason of their not being dissolved 

 is the following, and it may in justice be taken 

 as an example of those wise provisions of nature, 

 whereby what is useful is never wasted, and yet 

 is at all times ready to be abundantly supplied. 



" These alkalies exist in combination with 

 the various other ingredients of the rock in 

 which they occur, and in this way have such a 

 powerful attraction for those ingredients that 

 they are capable of completely resisting the sol- 

 vent action of water as long as the integrity of 

 the mass is sustained. When, however, it is 

 reduced to a perfectly impalpable powder, this 

 attraction is diminished to a considerable extent, 

 and then the alkali is much more easily dis- 

 solved. Now this is the case in soil, and conse- 

 quently while the stony portions of the soil 

 contain a vast supply of these valuable ingre- 

 dients in a condition in which water can do 

 them no injury, the impalpable powder is sup- 

 plied with them in a soluble state, and hence in 

 a condition available to the wants of vegetation. 



" In the rocks which we have mentioned the 

 alkalies are always associated with clay, and it 

 is to this substance that they have the greatest 

 attraction: it follows, therefore, that the more 

 clay a soil contains, the more alkalies will it have ; 

 but at the same time it will yield them less 

 easily to water, and through its medium to 

 plants." 



The following analysis of a soil, drawn up by 

 Baumhauer of Utrecht, from a tract in North 

 Holland gained by embankment from the 



sea, without reference to its barrenness or ferti- 

 lity, is given by Mr Stephens, in order to show 

 the great variety of substances contained in it, 

 and also how important they are in the growth 

 of plants : — 





Soil 

 (surface). 



Subsoil, 

 15 inches 

 deep. 



Subsoil, 

 30 inches 

 deep. 



Organic matter and water 









combined, . 



8.324 



7.700 



9.348 



Humic acid, . 

 Crenic acid, . 



2.798 



3.911 



3.428 



0.771 



0.731 



0.037 



Apocrenic acid, 



0.107 



0.160 



0.152 



Potash, 



1.026 



1.430 



1.521 



Soda, 



1.972 



2.069 



1.937 



Ammonia, 



0.060 



0.078 



0.075 



Lime, .... 



4.092 



5.096 



2.480 



Magnesia, 

 Peroxide of iron, . 



0.130 



0.140 



0.128 



9.039 



10.305 



11.864 



Protoxide of iron, . 



0.350 



0.563 



0.200 



Protoxide of manganese, 



0.288 



0.354 



0.284 



Alumina, 



1.364 



2.576 



2.401 



Phosphoric acid, . 



0.466 



0.324 



0.478 



Sulphuric acid, 



0.896 



1.104 



0.576 



Carbonic acid, 



6.085 



6.940 



4.775 



Chlorine, 



1.240 



1.382 



1.418 



Soluble silica, 



2 340 



2.496 



2.286 



Insoluble silicates, 



57.646 



51.706 



55.372 



Loss, .... 



1.006 



0.935 



1.231 





100. 



100. 



100. 



" On comparing the constituents of such a 

 soil as the above with the mineral ingredients 

 obtained by incineration from the ashes of 

 plants, it is found that plants withdraw from the 

 soil chiefly its alkaline, mineral, acid, and earthy 

 ingredients ; and if all these were not essential 

 to the very existence of the plants, they would 



