324 
CHEMISTRY OF HORTICULTURE. — LIME. 
CHEMISTEY OF HOETICULTUEE.— LIME. 
By John Towers. Esq, 
(Continued from Page 294.) 
The Compounds of Lime, which now form our subject, are, in many instances of great 
importance to the cultivator. Chalk, that is, carbonate of lime, according to Professor 
Brande, is the most abundant compound of this earth ; its elements, which are pure lime 
and carbonic acid, combine in the proportional equivalent of 56 of the former to 44 of the 
latter in the 100 parts. Carbonate of lime, as distinct from rock-chalk, exists naturally 
in a great variety of forms, some of them possessing much beauty. Among these are all 
the varieties of marble, crystallised calcareous spar, Iceland spar, transparent, with a 
doubly refractive power : the Stalactites of the caverns of Derbyshire furnish magnificent 
specimens. It is there we find it deposited from its solution in water acidulated by the 
carbonic acid, and substances immersed in this water become incrusted by carbonate of 
lime, when the excess flies off, as seen in the petrifying well at Matlock. 
The process of petrifaction has neither been well understood, nor defined : the word, 
as derived from the Latin, implies a conversion of the substance so changed into stone. 
But objections have been urged against this, " because a very considerable number of the 
plants, shells, and the bones of vertebrated animals enclosed in rock are not at all 
petrified ; " whereas the process of conversion into stone {lapidification) has been perfectly 
effected in objects of comparatively recent date, never imbedded in the earth, as the wood 
of a Roman aqueduct in Westphalia. There are also petrifying streams of water, into 
which small branches of trees that have fallen, and remained long immersed have, to all 
appearance lost the properties of wood, still however retaining the form of every vessel or 
cell in perfection. These facts do not bear strongly upon the processes of horticulture, 
otherwise than as they tend to impress upon the gardener the necessity of depriving any 
hard water which he may be constrained to use, of the excess of carbonic acid, by the 
addition of quick lime, in the manner and proportion described at page S61. 
Sulphate of Lime — Gypsum, Plaster of Paris, is a mineral found in England, and 
■when in masses is called Alabaster. The stone or rock-gypsum, being powdered, is, by 
a process called dry-hoiling, reduced to the condition in which it is so extensively used as 
Plaster of Paris. It is found abundantly near Paris, where it forms the hill of Mont- 
martre. The selenitic sulphates of lime occur in clays ; particularly in the Oolitic, and 
are now produced among the diluvial clays, as at Scarborough clifi". 
The crystallised sulphate of lime consists of 
Dry or Anhydrous Sulphate, 1 part . . . , — 68 or, per cent. 79 
Of water in combination, 2 parts . . . . . zir 18 „ 21 
Bry Gypsum is soluble in about 500 parts of water at 60°, and in 450 parts at the 
boiling point = 212°. As sulphate of lime is more soluble in water than pure lime, 
which latter has been seen to require at least 750 of water, no precipitation is caused, or 
sediment deposited when sulphuric acid is added to lime water. 
As I before stated, some portion of Gypsum is very frequently detected in those waters 
which are called hard; generally however, it exists in smaller proportion than chalk, 
though often in company with it, as I have proved by a variety of tests. 
Water that contains a little Gypsum, alone, cannot prove injurious to plants, particu- 
larly those of the iMpilionaceous order, for on such — as clover, peas, beans, vetches, sainfoin, 
and lucern — it was found most useful on the farm. Here, as in all theories upon which 
there exist doubts, nothing can be received which has not been proved by accurate 
analyses, repeated under every possible circumstance, of the living plant and its juices. 
If sulphate of lime be bond fide so detected, then we may safely conclude that the ground 
upon which the plant has grown contains more or less of that inorganic compound, which 
could not possibly be produced by the atmosphere, or absorbed by the leaves. 
It is stated, and is a fact worthy of record, that the great Benjamin Franklin was the 
