XXVI. Who judging by general or common principles, would not conclude, that wet hay was much less liable to take fire than dry? But experience teaches us, that by putting together quantities of hay too moist, it will take fire of itself, which could never have happened, if the hay had been put together sufficiently dry, or more thoroughly made. XXVII. What maxim is better established, or more generally assented to among the naturalists, than that a vivifying heat of the blood, is indispensably necessary for the preservation of life? But with all this, Father Plumier, a learned priest of the order of Minimus, in a voyage in the Pacific ocean, for want of water, found himself under a necessity of drinking the blood of turtles, and declares, he found it as cold as the common water in Europe. (Mem. de Trevoux, an. 1704, tom. 1. page 175.) Who, agreeable to the laws of ratiocination, can say otherwise, than that the third quality, resulting from the mixing three or four fœtid things together, must be fœtid also? But experience manifests to us, that this consequence is not infallible. Mr. Lemeri bought a certain quantity of the gums galbanum, sagapenum, and opopanax, and also some bitumen of Judæa, which he put all together into a retort, and found that there resulted from the mixtures, a strongly scented oil, greatly resembling musk; now the bitumen in smell, does not in the least resemble musk, and the other three drugs are absolutely fœtid. (Hist. de l’Academ. Royal, ann. 1706.) XXVIII. If a philosopher, destitute of all other information, except that which he had acquired in the schools, should be told that two liquids, which to the touch appear cold, should upon being mixed together, not only heat and boil, but also emit a flame; he would be in a terrible agitation, and armed with his infallible conclusive principle, _that nothing can communicate a quality which it does not possess_, would exclaim against the proposition. But let him exclaim as much as he will, it is a certain fact, that from mixing a pure acid, with the essential oil of an aromatic plant, there will result that commotion. XXIX. We know that water, is much heavier than air; and we also know, that the vapours which arise from the earth, are nothing else but particles of water, very minutely divided, and consequently, that they must be much heavier than particles of air of the same size. We know also, that a liquid cannot ascend above another, when they are put together, except when it’s particles of equal size are lighter than those of the other. From these premises, it should follow as an infallible consequence, that these vapours cannot rise superior to the air we breathe. But let this consequence appear ever so infallible, experience convinces us that the fact is otherwise.