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AGRICULTURAL CHEMISTRY. 
The quantity of oxygen is too nearly the same 
in the bases of the pines, although the bases vary, 
to suppose it accidental; and in the fir trees, 
after deducting the oxygen of the bases which 
were combined with phosphoric, sulphuric, and 
chlorohydric acids, the remainders are 11°62 and 
11'47 respectively. Hence the quantities of 
oxygen being the same, equivalent quantities 
of bases are saturated although these vary ma- 
terially. 
“Tf potatoes are grown where they are not 
supplied with earth, the magazine of inorganic 
bases (in cellars for example) a true alkali, called 
solanin, of very poisonous nature, is formed in 
the sprouts which extend towards the light, 
| while not the smallest trace of such a substance 
| can be discovered in the roots, herbs, blossoms, 
_ or fruits of potatoes grown in fields. 
“The conclusion to which all the foregoing 
facts lead us is, that the alkaline bases existing 
in the ashes of plants must be necessary to their 
growth, since if this were not the case they would 
not be retained. 
“Mhe perfect development of a plant accord- 
_ ing to this view, is dependent on the presence of 
_ alkalies or alkaline earths; for when these sub- 
| stances are totally wanting, its growth will be 
| arrested, and when they are only deficient, it 
| must be impeded.” 
Ten thousand parts of oak-wood yield 250 
| parts of ashes, the same quantity of fir-wood 
only 83, of linden-wood 500, of rye 440, and of 
the herb of the potato-plant, 1,500 parts. 
Firs and pines find a sufficient quantity of al- 
kalies in granitic and barren sandy soils in which 
oaks will not grow; and wheat thrives in soils 
favourable for the linden tree, because the bases 
which are necessary to bring it to complete ma- 
turity, exist there in sufficient quantity. 
The Equisetacese and all the genera of grasses 
contain in the outer parts of their leaves and 
stalk a large quantity of silicic acid and pot- 
ash in the form of acid silicate of potash. The 
proportion of this salt does not vary percepti- 
bly in the soil of corn-fields, because it is again 
conveyed to them as manure in the form of 
putrefying straw. But this is not the case ina 
meadow, and hence we never find a luxuriant 
crop of grass on sandy and calcareous soils, which 
contain little potash, evidently because one of 
the constituents indispensable to the growth of 
the plants is wanting. Soils formed from basalt, 
greywacke, and porphyry, are, ceteris paribus, 
the best for meadow-land, on account of the 
quantity of potash which enters into their com- 
position. The potash abstracted by the plants is 
restored under the annual irrigation. 
A harvest of grain is obtained every 30 or 40 
years from the soil of the Luneburg heath, by 
strewing it with the ashes of the heath-plants 
(Zrica vulgaris) which grow on it. These plants 
during the long period just mentioned collect the 
potash and soda which are conveyed to them by 
(o> 
rain-water; and it is by means of these alkalies 
that oats, barley, and rye, to which they are in- 
dispensable, are enabled to grow on this sandy 
heath. 
A proprietor of land in the vicinity of Gottin- 
gen, in order to obtain potash, planted his whole 
land with wormwood, the ashes of which are 
well known to contain a large proportion of the 
carbonate of that alkali. The consequence was, 
that he rendered his land quite incapable of 
bearing grain for many years, in consequence of 
having entirely deprived the soil of its potash. 
The supposition that alkalies or inorganic mat- 
ter in general are generated by plants is refuted 
by these facts. Steam and vapours have a re- 
markable power of transporting solid fixed mat- 
ter, either in the form of a gas or dissolved in 
one. 
It is known that in sea-storms, leaves of plants 
in the direction of the wind are covered with 
crystals of salt, even at the distance of from 20 
to 30 miles from the sea. But it does not re- 
quire a storm to cause the volatilization of the 
salt, for the air hanging over the sea always con- 
tains enough of this substance to make a solution 
of nitrate of silver turbid, and every breeze must 
carry this away. Now, as thousands of tons of 
sea-water annually evaporate into the atmosphere, 
a corresponding quantity of the salts dissolved in 
it, viz. of common salt, chloride of potassium, 
magnesia, and the remaining constituents of the | 
sea-water, will be conveyed by the wind to the | 
land. 
By the continual evaporation of the sea, its | 
salts are spread over the whole surface of the | 
earth; and being subsequently carried down by | 
the rain, furnish to the vegetation those salts | 
This is the origin of | 
necessary to its existence. 
the salts found in the ashes of plants, in those | 
cases where the soil could not have yielded them. 
Art of Culture—Carbonic acid, ammonia, and 
water yield elements for all the organs of plants. 
Certain inorganic substances—salts and metallic 
oxides—serve peculiar functions in their organ- | 
ism, and many of them must be viewed as essen- 
tial constituents of particular parts. , 
The atmosphere and the soil offer the same 
kind of nourishment to the leaves and roots. | 
The former contains a comparatively inexhaus- 
tible supply of carbonic acid and ammonia; the 
latter, by means of its humus, generates con- 
stantly fresh carbonic acid, while, during the 
winter, rain and snow introduce into the soil a 
quantity of ammonia, sufficient for the develop- 
ment of the leaves and blossoms. 
In whatever form we supply plants with those 
substances which are the products of their own 
action, in no instance do they appear to have 
any effect upon their growth, or to replace what | 
they have lost. Sugar, gum, and starch, are not 
food for plants, and the same must be said of 
humic acid, which is so closely allied to them in 
composition. 
