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Updated: May 6, 2025
The materialism of the preceding century was overwhelmingly mechanical, because at that time of all the natural sciences, mechanics, and indeed, only the mechanics of the celestial and terrestrial fixed bodies, the mechanics of gravity, in short, had reached any definite conclusions. Chemistry existed at first only in a childish, phlogistic form.
In addition to these advantages, the phlogistic theory was based on experiments, and led to experiments, the results of which proved that the capacity to undergo combustion might be conveyed to an incombustible substance, by causing it to react with some other substance, itself combustible, under definite conditions.
Its supporters disagreed among themselves, first as to the explanation of certain phenomena that did not seem to accord with the phlogistic theory, and a little later as to the theory itself. But as yet there was no satisfactory substitute for this theory, which, even if unsatisfactory, seemed better than anything that had gone before or could be suggested.
Whether he thought it sailor-like, or whether his tailor was afraid of putting his lordship to short allowance of cloth, for fear of phlogistic consequences, I know not; but broad as was the beam of his lordship, still broader and more ample in proportion were the folds of this essential part of his drapery, quite enough to have embraced twice the volume of human flesh contained within them, large as it undoubtedly was.
According to the phlogistic theory, the part remaining after a substance was burned was simply the original substance deprived of phlogiston. To restore the original combustible substance, it was necessary to heat the residue of the combustion with something that burned easily, so that the freed phlogiston might again combine with the ashes.
Here is a proposition which should be well considered, before it be admitted as a principle, which shall establish the perpetuity of these mountains, if it be true; or, if false, assure us of their future demolition. Let us now examine it. That which preserves vegetable bodies so long from dissolution in water, is what may be called the inflammable or phlogistic composition of those bodies.
Hoefer says, in his Histoire de la Chimie, "If it is true that simplicity is the distinctive character of verity, never was a theory so true as that of Stahl." The phlogistic theory did more than serve as a means for bringing together many apparently disconnected facts.
This theory fitted very nicely as applied to the calcined lead revivified by the grains of wheat, although with some other products of calcination it did not seem to apply at all. It will be seen from this that the phlogistic theory was a step towards chemistry and away from alchemy.
But, from his chemical experiments, our author has conjectured that there may be a phlogistic substance, by means of which the siliceous earth is dissolved when in darkness; and that this solvent loses its power, if exposed to the light of day. I have one observation to oppose to this ingenious theory.
The abandonment of the phlogistic theory is an illustration of the readiness with which scientific hypotheses are surrendered, when found to be wanting in accordance with facts. Authority and tradition pass for nothing. Every thing is settled by an appeal to Nature. It is assumed that the answers she gives to a practical interrogation will ever be true.
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