204 
CULTURAL CHEMISTRY. 
or less of ammonia, but, to be rendered of any avail to vegetation, they must be 
incorporated with the soil : there they are in their natural position ; the moisture of 
the ground, and every falling shower, liquefy the saline particles of the manure, and 
thus qualify the doses. Guano, if pure, abounds with salts of ammonia, and these 
are also soluble in water ; hence the gardener who employs this foreign manm'e with 
great caution, may derive some advantage by applying it in the condition of a very 
weak solution. Hence, also, the farmer (as the converse of the former condition) 
has always found that guano, in the dry way, among tender seeds, does great injury; 
and also that, in a dry season, it rarely produces any good effect on the land, how- 
ever it may have been applied. Finally, all experience teaches that the roots are 
the channels of nutriment, and that if the required quantity of enriching matters be 
absent from the soil, luxuriance can never be promoted ; and moreover, especially if 
there be any serious deficiency of ground moisture, every appliance to the leaves oz 
parts above the surface is completely ineffectual. In pot-culture^ the daily attendant 
of the plant-houses, requires no philosopher to instruct him how to keep his plants 
alive. .He may, indeed, drench the floors with water ; he may fill the entire capacity 
of his vinery with steam, to saturation ; but he is perfectly aw'are that, although he 
may thereby obviate the attacks of red spider, and, in a degree, refresh the foliage, 
he must depend solely upon the moisture of the soil for the preparation and supply 
of the vital sap. Surely no more need be said upon a subject so plain to the under- 
standing ; yet by no means would we dogmatically assert, that the theory of absorp- 
tion by the leaves is a fallacy. We are sure that facts are adducihle, and of hourly 
occurrence, to demonstrate that the leaves exhale watery matter, and therefore that 
the destruction of any foliage effects a corresponding injury on the vital energy of 
any plant. But we are not equally certain that vegetables naturally mhale, that is, 
attract and absorb carbonic acid, ammonia, or any hydro-carbon, as nutriment, from 
the atmosphere ; and therefore, being certain on the one important function, but 
doubtful of the other, we dare not assert as proved, that which has never been seen 
to exist, and, at the most, amounts only to an opinion of recent formation, based on 
a few experiments conducted upon principles, and with apparatus, at variance with 
the natural condition of vegetable existence. 
Our subject has grown upon us, and will demand a second article, wherein the 
aqueous, inorganic, or mineral elements must be considered. At present it must 
suffice to observe, that Chemistry has proved beyond a doubt, that much of mystery 
certainly exists, very little of which is as yet clearly unravelled. Organic Analysis 
has yielded proof, of the infinite modifications which are traceable in the vegetable 
subject, although the elements revealed are only four. Thus we have just attained 
the threshold, but have not taken one step in advance beyond it. Fortunately 
for the gardener, his practical skill has taught him that if he can command a soft 
and unctuous loam, a mass of pure reduced leaves, and a quantity of heath-mould of 
two kinds, he can work with confidence of luxuriant results, although he, in common 
with the greatest philosopher of the land, is profoundly ignorant of first causes. 
