58 
GARDENING AS A SCIENCE. 
it is shown that the fir-wood of Norway reduced to ashes contains in every 
100 parts :— - 
Potash 14-1 tenth 
Soda 207 „ 
Lime . -. . . . . . 12-3 „ 
Magnesia 4-35,, 
5145 
that is, more than one half the weight of the ashes of chemical salts. 
Whence could these constituents have been derived ? To this question the only 
possible answer is, from the earth ! But the ground in the pine-forests of Norway 
is not laboured or manured by man, and the trees have grown therein for time 
immemorial. Sand contains no trace of any of the four salts, and the vegetable 
matters incorporated with the soil are the actual products of the decayed leaves of 
the fir-trees themselves : we therefore must refer the salts to the loam, or even 
clay of the district, and upon this subject Liebig remarks, — 
" Arable land is originally formed by the crumbling of rocks and its properties 
on the nature of their principal component parts. Pure sand and pure limestone 
form absolutely barren soils ; but argillaceous earths (clays, or alumina) form 
always a part of fertile soils. It is known that the aluminous minerals are 
the most widely diffused on the surface of the earth ; and all fertile soils, or soils 
capable of culture, contain alumina as an invariable constituent. There must 
therefore be something in aluminous earth which enables it to exercise an influence 
in the life of plants, and to assist in their development. The property on which 
this depends, is that of its invariably containing potash and soda." 
Now, admitting this chemical principle to be correct, the use we would make 
of it may be explained : Gardening, like Agriculture, will never be understood, nor 
its phenomena interpreted, until, by analyses, the products of burning be clearly 
revealed. If, by any well-conducted experiments, it is proved that an alkali — as 
soda, potash, or lime, exist in the ashes of a plant, that plant will require loam as 
its staple earth ; and as potash is present in loam of every description, as a 
necessary result of the disintegration of mineral rocks, it is reasonable to ascribe to 
potash or soda the fertilizing power of loams on those plants which demand an 
adequate supply of those alkalies. 
The rocks which appear to be the grand magazines of alkali are felspar,— said 
to contain above 17 parts in the 100 of potash ; albite llf- of soda ; zeolite 13 to 
1 6 of both alkalies together. 
This general statement, based as it is upon the authority of several of the most 
profound analytic chemists, will show, at a glance, how greatly loams must vary in 
character ; will it then be at all surprising that cultivators must experience disap- 
pointment in their attempts to imitate the practice of a neighbour, whose material 
does not accord with the earth to which he himself can solely have recourse ? But 
this is not all : one loam, while it contains three times the proportion of salts, may 
differ essentially from another in the texture or mechanical mixture of the required 
