260 
CHEMISTRY OF HORTICULTURE. — -WATER. 
Water distilled from stone or glass vessels, free from metallic contact, might represent 
it, but neither the one nor the other would be fit for the table, being void of the air which 
is required to confer briskness of flavour. Rain Water is by no means free from impu- 
rities, particularly those derived from soot conveyed into the atmosphere. Hence, the 
presence of volatile carbonate of ammonia that can be detected by chemical re-agents. 
Locality must in a great degree affect the character of Rain Water, which accordingly, is 
said to yield traces of some muriates, of free muriatic and nitric acid, carbonic acid, carbu- 
retted hydrogen, and also of minute quantities of the metals, iron, nickel, and manganese. 
Rain Water collected chiefly by the roofs of glazed erections, and retained in under- 
ground tanks, exposed to the influence of air by gratings, is one of the chief resources of 
the gardener, unless he happily is supplied with a rill, or other constant source of sweet, 
soft Water, which is almost invariably impregnated with some portions of vegetable or 
animal matter. 
River Water varies much in quality ; if it originate in springs, augmented by Rain 
Water, and flow over a granitic or stony channel, it may be very pure, and sufficiently soft 
for all the objects of horticulture. The Water of the Thames has lately become the 
subject of much solicitude, in consequence of the numerous adventitious impregnations of a 
disgusting nature from the sewage of the Metropolis. I do not pretend to interfere with 
the plans of improvement now contemplated, particularly those suggested by Mr. Jasper 
Rogers, which embrace considerations of vast moment, involving not only the public health, 
but the prosperity of agriculture. But, so far as chemical agency is concerned, it will he 
requisite to enter somewhat at large upon the means by which it is proposed to effect the 
improvement of hard Waters, and thus, at once, to correct one of the great inconveniences 
to which many gardeners are inevitably subjected. 
Hardness of River and Spring Water varies exceedingly : it is generally occasioned by 
chalk, in different quantities, held in solution by carbonic acid. Professor Clark, of 
Aberdeen, has conferred great benefit upon the public by his able report of a process by 
which the hardest Waters can be rendered comparatively soft, so as no longer to destroy 
much soap before a lather can he produced ; and consequently fitted for the purposes of 
horticulture. In a recent investigation of the very defective Waters in and about Croydon, 
many facts came to light, the discovery of which afford promise of great amelioration. In 
the first place, chemical analyses have proved that the Water from wells situated in 
different parts of the town contained chalk, some to the extent of 48°, others diminishing 
through various grades, to 22° and 17^° of hardness, “each degree indicating as much 
hardness as would be produced by one grain of chalk per gallon.” 
If, then, the waters of Croydon, within the radius of a circle short of 1 mile from its 
centre, evidence so much variety, we may safely conclude that other localities are in a 
similar predicament with respect to the Waters in ordinary use. 
River Water, if we assume that of the Thames and New River as a standard (to say 
nothing of the taint acquired from foul impregnations), contains far too large a quantity of 
chalky matter. Dr. Clark stated that, “ One hundred gallons of the Waters of London 
supplied by the Companies, take from twenty-four to thirty-two ounces of the best curd-soap 
in order to form a lather of such consistence as to remain all over the surface for five 
minutes.” 
By his new process (and its theory) shortly to be described, Dr. Clark proposed to 
reduce the hardness of the London Waters, so far that about one-third of the soap now 
required, should suffice to produce a complete lather similar to the one above alluded to. 
Theory. — Chalk is almost, or altogether insoluble in water, but it may be rendered 
soluble by two processes of a very opposite kind. 
1 . When burned in a lime-kiln, chalk and lime-stone lose weight. If dry and pure, 
the pound of sixteen ounces will produce only nine ounces of completely burnt lime, 
therefore, seven ounces have been driven off by the fire, and these seven ounces consist of 
carbonic acid — that aerial gas which was noticed in an article on atmospheric air. Chalk 
so burnt becomes quick lime, of which the aforesaid nine ounces will be soluble in pure 
water, but they will require not less than forty gallons of such water for their complete 
