the present views, over the philosophers and chemists of modern Europe. According to this philosopher, then, combustion was merely the evolution from the burning body, when placed in circumstances adapted to this effect, of a peculiarly subtile and active principle, to which, from the ordinary appearance which its evolution assumes, he gave the name of Phlogiston—light and heat being those properties of this body by which it adapts itself to the observation of our powers of perception. This theory, we have said, from the high reputation which its author had obtained, was long unanimously adopted by philosophers—and being in perfect agreement with the most natural and obvious judgment of mankind, scarcely a suspicion was allowed to intervene, that there could be any thing imperfect or inaccurate in the theory. The progress of philosophical opinion upon this subject, however, presents, we think, a very instructive instance of a disposition which seems universally characteristic of mankind, that, we mean, of employing any favourite principle to account for every appearance which presents itself, however little warranted such an application may be by the circumstances most characteristic of the phenomenon in question. It is accordingly very generally known, that about the latter part of the last century, and while the doctrines of Stahl were in all their vigour, the existence and properties of oxygen were discovered, and immediately excited the utmost attention in all who were devoted to philosophical pursuits. The discovery was, in reality, both beautiful and instructive in a very uncommon degree. The increased illumination communicated by this gas to any ignited body which the operator immersed in it—the pure and apparently etherial nature of the gas itself—the very energetic properties it was found to possess—and the vast variety of bodies into whose composition it was discovered to enter—all contributed to point out this substance as one of the most important instruments in the economy of nature, and insensibly produced a very general disposition to receive its operation as a complete account of any former unexplained phenomena, with whose existence and properties it might have any connexion. While the minds of men, accordingly, were in this state, it was opportunely discovered, that when a burning body is introduced into a jar of common air, the mouth of the jar being at the same time inverted over water, the oxygenous portion of the air is altogether consumed, and the burning body is found to have acquired an additional weight, precisely corresponding with that of the oxygen which had disappeared. From this discovery it was immediately concluded, that combustion is in fact nothing else than the combination of oxygen with the combustible body—that the light and heat are the consequences of this combination, being necessarily given out by the combining oxygen—and that the whole process of combustion is explained, when it is stated to be the consequence of the separation of oxygen,—first, from the other constituent of the air, and next, from the light and heat which it contained before it began to experience this separation,—and also, of the combination of this gas with the body whose combustion was actually observed. A few of the more intelligent and cautious of the learned might still entertain a very invincible opinion, that the phenomenon in question had not really been accounted for but the great multitude of the studious, who seldom condescend to a very careful examination of any particular subject, received the doctrine as impregnably established—while, in the public demonstrations of professed teachers, the difficulties that remained were either entirely unnoticed, or were hastily concealed from the view of the curious, by ambiguous language, or unsatisfactory conjecture.
From the application of this statement, however, we conceive ourselves bound to exempt all the more enlightened and illustrious chemists. Sir Humphry Davy, we believe, in his public lectures, always expressed himself upon this subject with much becoming freedom of opinion and Dr Thomson has repeatedly stated, in his excellent system, that he still considered the explanation of the phenomena of combustion as in a very imperfect state. The opinion of this latter philosopher, indeed, if we are not much mistaken, has always coincided exactly with that which we are anxious at present to submit to the
