July r, i88t.] 
THE TROPICAL AGRICULTURIST. 
157 
lime as the carbonic acid did, it appropriates 1 12 
parts, forming gypsum in this case, instead of chalk, 
as in the former, and leaving the new compound— 
namely, superphosphate of lime, — to possess the fol- 
lowing composition ; lime by weight, 56' parts, phos- 
phoric acid, 142 parts ; and water, 3G parts. So now 
we have less lime by 5G parts, and more water by 
18 parts. 
The gypsum formed artificially in the manufacture of 
this 234 parts of superphosphate amounts to 272 pnrts, 
and the two bodies are in a state of intimate mix- 
ture, and so remain to be sold as is well understood as 
superphosphate of lime and some manufacturers further 
add large (|uautities of ground gypsum as a "drier." 
Therefore commercial superphosphate is very largely 
made up of gypsum, it was found that mineral phos- 
phates, such as copiolites, might be mixed with the 
bones without seriously interfering with the quality 
of the manure, and it is now often the practice to 
mix equal quantities, and afterwards treat the mix- 
ture with the sulphuric acid. This has the effect 
of keeping the price within reasonable limits. The 
action of superphosphate dopends greatly upon the 
composition of the soil to which it is applied. Leaving 
the gypsum for the present out of consideration, it 
is found that, if there are no free basic substances 
osphate 
growth; 
e plant 
Is to till 
sup^ 
or carbonates present iu the soil, 
is quickly dissolved, and causes ra 
but its effects are quickly exhai 
then fails to acquire tliat nourisl 
its cells in the later stages of its gi 
Hut it almost always happens 
or less lime, or carbonate of lime, 
immediately seizes upon a portio 
acid of the superphosphate, and 
same compound as that obtained 1 
bones which compound is the mea 
insoluble tricaleie phosphate and 
Buperphosphate of lime. This 1 
also the form of the so-called 1 
phates," which from age and co 
stances have lost some of their 
though thereby they have become 
ated in value, their practical 
purposes increased. So, as a r 
phate has been applied to land, 
similar to fermented bon is, with 
however, viz., that the former c< 
its w« ight of gypsum j and somt 
usually ascribed to supcrphosph 
presence in its composition of th 
sulphate of lime. Superphosphati 
in small quantities to turnips, 9 
soils that are ihort of phosphorii 
often be found that a dressing o 
bone dust and soot, &c„ would be equally efficacious at 
a less cost. 
Carbonate of lime, iu the form of chalk, mail, 
shell- sand, &c., is sometimes used for applying t> 
land, and in somo cases it has its advantages ov r 
hot limo ; for though it does not decompose the 
silicates, it does not use up the organic matter, and 
therefore is better adapted for li^ht soils, which have 
not any organic matter to spare. It can also some- 
times be obtained at u very cheap rate, and, where 
lime is dear, economical reasons may dictate its u*e. 
It is useful for neutralising free acids in soils, and 
so sweetening the herbage; but it is lumpy and 
insoluble, and ditlicult to deal with, and, with 
manufactured lime and ground gypsum at reasonable 
price", chalk is Dot likely to be used to anj extfllH 
by practical people. 
Sulphate of lime is found naturally iu the form "t 
gypsum, which is composed of lime, ."i(> parts, dry 
sulphuric acid, 81) parts, and water, 3t> parts, by 
weight. This requires grinding before is available 
f< r use, and it can now be obtained in the foi m of 
40 
kit there is more 
the soil, and this 
if the phosphoric 
ives precisely the 
he fermentation of 
let with basic sub- 
osphoric acid ; and 
nmercially dtpreci- 
lity has for many 
i, after superphos- 
becomes exactly 
e great difference, 
nius at least half 
f the good results 
are due to the 
largo proportion of 
honld be applied 
les, &c., and to all 
cid ; but it would 
lypsum mixed with 
powder at a very moderate cost. The sulphate of lime 
is useful as plant food, whenever a soil requires lime 
or sulphuric acid. Lime is present in most soils, but 
many districts are very deficient in sulphuric acid, 
and ground gypsum is the most convenient and the 
cheapest form of sulphuric acid to apply. Where a 
sandy soil requires lime, in which case quick lime is 
objectionable, gypsum answers the purpose admirably. 
It is portable, eisily spread, aud slowly soluble, and 
it assists such light soils, both mechanically and 
chemically, in retaining ammoniacal and other manures 
that are applied to them. This form of lime is an 
excellent top dressing for clover, which requires both 
the lime and the sulphuric acid that it furnishes. 
Dry clover contains five parts in a thousand of 
sulphur, aud only two parts in a thousand of phos- 
phorus, so that in thi-> case it is absolutely necessary 
to add a sulphate to the soil as a manure. Sulphate 
of lime is a capital manure for mangolds, the long 
red variety in particular taking away more sulphuric 
than phosphoric acids. It should be applied largely 
upon all lands where sheep and other stock are 
kept, as all animals require sulphur. With regard 
to this, Johnstone states that wool contains 5 per 
cent, of its weight of sulphur, and he says th» wool 
grown in Great Britain and Irland cirries off four 
million pounds of sulphur aunually, and calculates 
that to make up for this loss alone 300,000 tons of 
gypsum should be applied to the laud every year. 
He goes on to say that the hair growu by the popu- 
lation adds fifty per cent, to these figures : and, if we 
consider the quantity of hair grown by cattle, horses, 
domestic animals, and vermin, it must be seen that 
if this were added to Johnstone's calculation the 
latter would be enormously increased. Sulphate of 
lime is also an excellent manure for all leguminous 
crops as beams, peas, &c. It should always be applied, 
with farmyard and other ammonicol manure*, to all 
crops, as it reacts with ammonia, and forms Sulphate 
of ammonia, instead of the carbonate, aud so saves 
a most valuable plant food, viz.. nitrogen, which 
would otherwise, from its volatility as ammonia, be 
entirely lost. 
By seattcring gypsum daily over manure heaps, 
stable floors, and in closets, etc., an immense quantity 
of nitrogen is saved, the value of which, could it 
be calculated, would reach a suqjrising amount. 
The best results may be obtained by using gypsum 
with guano, houe dust, shoddy, rags, soot, and other 
nitrogenous and phosphatic manures, and it would 
probably be found that a mixture of bone dust and 
gypsum would produce a more lasting effect at a 
a cheaper rate than would the application of super- 
Those who use gypsum a* a top-dressing prefer to 
sow iu dewy m rnings or evenings, or during a slight 
shower of rain, so that it clings to the leaves of the 
pla"t, and they say that its effects, when it continues 
for some time on the leaves, are very remarkable. 
Moreton's "Cyclopaedia of Agriculture " holds with 
this view, and gives some striking instances of the 
action of gypsum iu this way. To account for this, 
it has been suggested that tho well-known reaction 
of gypsum with ammonia (the latter obtained from 
the air) takes place on the leaves, and that ammonium 
sulphate (and chalk) is formed ; but the explanation 
generally coes no further. From all the evidence ou 
the subject, we cannot doubt the truth of the general 
statement, but the explanation offered is not so clear. 
If the formation of sulphate of ammonia on the leaf 
produces such striking results, the inference would 
bo that the plant takes iu liquid food by its haves, 
which is quite contrary to the accepted idea that 
gaseous food only can enter in that way Or it might 
I'e that the sulphate of ammonia formed mi the 
leaves would be washed down to the ground near 
to the stem of the plant, and so in close proximity 
