CULTURAL CHEMISTRY. 
227 
began to form ? This and similar odours are due to the escape of volatile vapours 
from the leaves, which we have not yet sought to arrest or examine. The liquids 
which exude from leaves are no doubt various as their odours, their differences 
depending mainly upon the nature and the age of the plant. But there is reason to 
believe that they rarely consist of pure water. They hold in solution appreciable 
quantities of organic and saline matters, which, as the water evaporates from the 
leaf, remain behind upon its suface, or in its pores. These the rain washes off, and 
carries back to the soil ; and this is one of the destined functions of the rain in 
refreshing the growing plant." These are startling, yet real facts, and claim the 
most refined experiments of analysis. Liebig, in his zeal for the Absorption Theory, 
stated that the manure, buried and laborated within the soil, became the source 
of an atmosphere of carbonic acid, which rising to, and above the surface, floated 
among the growing plants, by whose leaves the gas was sucked in, and by organic 
agency w r as decomposed in the cells and tissues, thus becoming the main source of 
nutriment and growth. It is wonderful to observe the working of the imagination, 
when it indulges in the speculations of a fanciful hypothesis. In this instance, the 
offices of the roots appear to have been lost sight of. 
Coincident with this atmospheric theory was the opinion adopted by many of our 
modern lecturers, that plants obtain only mineral inorganic matter from the soil. 
Before we enter upon the analysis of this opinion, which, as Mr. Johnston told his 
audience at York, " had also received its death-blow," it will not be irrelevant to 
present to the reader the following tables of the component parts of sea-water, 
extracted from the Manuals of the two celebrated chemists, Dr. George Fownes and 
Professor Brande : it will be seen that great discrepancies exist, but these will not 
militate against the object which we contemplate. 
1st. Dr. Fownes, p. 109 — quoting the analysis of Dr. Schweitzer, of Brighton, 
the water being that of the Channel — 'gives 1000 grains as containing : — 
Grains. 
Chloride of Sodium (Common Salt) . . . . .27*059 
Chloride of Potassium (Muriate of Potash) . . . . -766 
Chloride of Magnesium (Muriate of Magnesia) . . . 3-666 
Bromide of Magnesium . . -029 
Sulphate of Magnesia (Epsom Salts) 2 296 
Sulphate of Lime (Gypsum) . . . . . . . 1-406 
Carhonate of Lime (Chalk) . . . . . . . -033 
Iodine and Ammoniacal Salt (Traces) 
Water (that is, in a state of purity) 964*745 
1000000 
"Its specific gravity was found to be 10274 at 60°. Sea- water is liable to 
variations of density and composition, by the influence of local causes, such as the 
proximity of large rivers, or masses of melting ice, and by other circumstances," one 
of which may be most important, namely, the flow of those vast subterraneous salt 
rivers which somewhere discharge their brine into the basin of the ocean. 
