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vernal and “ skyey influences”—how the stem produces the flower—how 
the flower produces the fruit. That it does, is outward and apparent. 
How it does, is invisible and mysterious. If man knew the process of 
vegetable growth he could produce it. We call it a chemical change, be¬ 
cause we can call it nothing else. It probably bears a greater analogy to 
what we call chemical changes than to any operation known to human 
sense. There are many of the natural phenomena for which we have 
plausible theories. The winds and tides, rain and^snow, attraction and 
heat, have received explanations, which, because not absolutely repulsive 
to reason, have received the sanction of the common sense of mankind. 
But of the means, the causes, the growth, the decay of vegetable life we 
have no theory. None has been suggested. None can be suggested 
The understanding is lost at the first attempt to produce a theory. No 
rational idea is held—none exists. It is one of those common mysteries 
which familiarity has stripped of awe, but which study has not solved, 
nor scrutiny exposed. 
There are other obstacles in the path of science. They are many, and, 
though not impossible, are difficult to overcome. A knowledge of them 
will not impair our confidence in the results which have been already de¬ 
monstrated, but will inspire us with a higher admiration for the triumph 
of human industry and genius, and a grander hope in their efficacy to 
achieve future triumphs. 
The constituents of soil that are deemed most valuable as sources of 
fertility are lime, potash, ammonia, organic matter, and phosphoric, sul¬ 
phuric and muriatic acids. The most fertilizing of these substances ex¬ 
ist in the minutest qualities. It is not difficult to ascertain the amount 
of organic matter in the soil, but nothing is known as to the essential 
portions in imparting vitality to new vegetation. It is not known whether 
the process of decomposition must be complete, whether it must be al¬ 
ready resolved into that fine pulverulent substance, the dusty and un- 
cognizable remains of organized growth, which we call humus, to render 
it valuable as a fertilizer,—or whether the gases generated by the pro¬ 
cess of decomposition are the sources of new growths and organisms. 
The volatility of chlorides during evaporation, and the presence of or¬ 
ganic matter, render exceedingly difficult and uncertain the determina¬ 
tion of muriatic acid. The precise estimation of potassa and phosphoric 
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