123 
Magnesian limestone—Cultivation of Wheats 
substances, both of organic and inorganic origin, 
which it is one of the functions of lime, when 
applied to the land, to combine with and render 
innoxious. But these acid compounds unite 
rather with the caustic magnesia, than with the 
lime which is already in combination with car* 
bonic acid—and form salts* which generally 
are much more soluble in water than the com¬ 
pounds of lime, with the same acids. Hence 
the water that goes to the roots, reaches them 
more or less loaded with magnesia salts, and 
carries into the vegetable circulation more mag¬ 
nesia than is consistent with the healthy growth 
of the plant 
It is hazardous to reason from the pheno¬ 
mena of animal to those of vegetable physio¬ 
logy, yet if lime and magnesia have the power 
of differently affecting the animal economy, 
why may they not also very differently affect 
the vegetable economy ? And since in the same 
circumstances, and in combination with the sub¬ 
stances they meet with in the same soils, mag¬ 
nesia is capable of entering more largely into 
a plant by its roots—may not magnesia be con¬ 
sidered capable of poisoning a plant, when lime 
in the same condition would only improve the 
soil 1 ? 
I have said that it may be doubted whether 
magnesia in the state of carbonate is wholly 
unhurtful to the land. This doubt rests on the 
fact that the magnesia retains its carbonic acid 
more feebly than lime does—and therefore its 
carbonate is the more easily decomposed when 
an acid body comes in contact with both. 
Though, therefore, the magnesian carbonate 
will not lay hold of all acid matter so readily 
and surely as caustic magnesia may, still occa¬ 
sions may occur where acid matters being abun¬ 
dant in the soil, so much carbonate of magnesia 
may be decomposed and dissolved as to render 
the water absorbed by its roots destructive to 
the health or life of a plant. 
In reference to this point, however, it must 
be distinctly understood, that magnesia is one 
of the kinds of inorganic food most necessary 
to plants, that a certain quantity of it in the soil 
is absolutely necessary to the growth of nearly 
all cultivated plants, and that it is only when it 
is conveyed to the roots in too large a quantity, 
that it proves injurious to vegetable life. 
5°. Sulphate of Magnesia —the common 
Epsom salts of the shops—is formed by dissol¬ 
ving carbonate of magnesia in diluted sulphuric 
acid. It exists in nearly all soils which are 
formed from, or are situated in, the neighbour¬ 
hood of rocks containing magnesia. In some 
soils it is so abundant that in dry weather it 
* Compounds of the bases ,— potash, soda, lime, 
magnesia, &c.,—with acids, —sulphuric, muriatic, ni¬ 
tric, acetic (or vinegar), &c.,—are called salts. 
forms a white efflorescence on the surface. This 
has been observed to take place in Bohemia 
Hungary, and parts of Germany, and it may 
be frequently seen in warm summer weather in 
the neighbourhood of Durham. 
This salt has been found by Sprengel to act 
upon vegetation precisely in the same way as 
gypsum does, and on the same kind of plants. 
It must be used, however in smaller quantity, 
owing to its great solubility. Its higher price 
will prevent its ever being substituted for gyp¬ 
sum, as a top-dressing for clover, &c., but it is 
worth the trial, whether corn plants, the grain 
of which contains much magnesia, might not 
be benefited by the application, of a small quan¬ 
tity of this sulphate—along with such other 
substances as are capable of yielding the re¬ 
maining constituents which compose the inor • 
ganic matter of the. grain. 
Cultivation of Wheat. — I this autumn 
tried an experiment on wheat sowing: our 
crops of wheat in this district are very apt in 
our clay soils on the banks of the Forth called 
Carie, to be thrown out in spring, by alternate 
nights of frost and days of sunshine, whereby 
the roots, if the plants are not entirely destroyed, 
are so injured that to support nature the plant 
puts out side shoots, and there being no firm 
hold of the ground, becomes what in England 
is called root-fallen, and lodges long before the 
grain is ripe, thereby producing grain of an in¬ 
ferior quality as well as quantity. To endea¬ 
vour to get the better of these faults, I tried 
what drilling my wheat as beans are drilled in 
our earns would do. I sowed my wheat by a 
plough drawn by two horses five or six inches 
deep, and covered it with the next furrow at 
ten or eleven inches breadth. I never harrow¬ 
ed it after sowing, and horse’s foot never trod on 
it. The wheat w T as covered by the deepest part 
of the furrow ; and to my surprize and that of 
my neighbours, the wheat thus sown and co¬ 
vered came up sooner than wheat sown the 
same day in the common broadcast way on 
some adjacent ground of similar quality, and 
the fallow treated exactly the same as to plough¬ 
ing, liming, &c, through the summer. As it 
is well known that wheat prefers a stiff’ soil to 
a loose one, I attributed the rapidity of growth 
to the stiff soil suiting the wheat more than the 
loose broadcast, for it not only came sooner, but 
kept the start it got, and now, after heavy rains 
and frost, looks better, the ground not being run 
together and battered with the winter rains, as 
the broadcast wheat is; and having examined 
it during severe frosts, I found that the roots of 
the plant had not suffered by it, whilst that sown 
broadcast had. The roots of the drilled wheat 
were actually considerably longer, than the 
