LIX. Although as Etmuller says, in matters of physics and medicine, _præstat unum experimentum centum rationibus_, still, the experiment just alledged is so defective, that it is not of more value than the arguments before urged. In the first place, dry wood, may as properly be called a mixture as green wood, notwithstanding which, it emits no water upon being laid on the fire. Secondly, as we are here treating of the elements in general which enter into, and make a part of the composition of every species of mixture, the fire should produce the same appearances, and have the same effect upon them, that it has upon the wood; but this does not happen, for minerals laid on the fire emit no water, unless it is when they have imbibed some foreign moisture. Thirdly, the chymists by means of fire differently applied, extract from wood and other mixtures, various substances, which differ from those four that are produced from the wood in the ordinary way of burning it; and it seems reasonable from hence, that we should augment the number of the elements. Fourthly, we do not know whether these substances pre-existed in the wood, or whether they were produced _de novo_ by the fire. Fifthly, the ash is not earth, nor an elemental or simple body as is supposed, for there may be separated from it a large portion of salt, which is a distinct substance from either of the four; for it is neither earth, air, water, or fire. Sixthly, neither is the smoke air, as is manifest from the soot which condenses in the chimney. If I should be told, that in the smoke is contained a variety of particles, some of which compose the soot, which remains in the chimney, and others which mount higher, and are impregnated with the atmosphere, and become air; I reply, that in consequence of this, they should admit of a fifth element of soot; or to speak more properly, of five or six additional elements; for Mr. Boyle informs us, that the chymists can extract from soot, five or six different substances. Finally, all that becomes ashes, existed before in the form of fire; from whence it follows, that the form of ashes is a new production, for matter cannot exist under two substantial forms at one and the same time; and consequently, the elemental form of earth which the Aristotelites ascribe to the ashes, could not pre-exist in the mixture, but must be a new production. This objection militates principally against the Aristotelic principles; but others might be formed in different shapes, against every system whatever. LX. I have combated only the Aristotelic opinion of the elements, not because the others are not incumbered with equal difficulties, and exposed to equal objections, but because in Spain, we suppose the others to be perplexing, and even improbable, and conclude that of the four elements, to be just and right; I therefore chose to attack this system, to let my countrymen see, that we know nothing with certainty respecting the elements. SECT. XIV.