V. Mons. Homberg, of the Academy Royal of Sciences, was the first who experienced this rare phenomenon, by resolving into smoak, with the focus of the burning-glass, at the Palace Royal at Paris, a great portion of its mass, which this celebrated chymist judged to be the mercurial part of the gold, and when this was gone, the residue which remained, appeared to be a terrestrial matter, mixed with somewhat of sulphur, that afterwards vitrified. So that in the opinion of Mons. Homberg, sulphur, and mercury, together with a portion of earth, is what gold is composed of, and although the two first are by their nature volatile, and capable of being dissipated and divided by the power of fire in all other metals, and in all other mixtures, they in gold are so intimately united, that no other force or influence can separate them, but that of the sun; it follows then, that the heat of the sun is much greater than that of elemental fire, and that this last cannot be hot in the highest degree, which is what we undertook to prove. PARADOX II. _The Air ought rather to be esteemed cold, than hot._ SECT. II. VI. The quality which Aristotle attributes to the air, is cold somewhat under the highest degree, or nearly approaching to the highest degree. Other philosophers, with more foundation of reason, esteem it indifferent to heat and cold; and I, without setting about to combat this second opinion, say it is more reasonable to suppose it cold than hot. Which I shall attempt to demonstrate in the following manner: in order to make a judgement of the qualities appertaining to a particular thing, we should consider it in a state, where it is divested of the influence of any extrinsic agent, by the operations of which it may be affected; the air then so circumstanced, will always be found to be cold; and from thence it should be inferred, that it naturally is cold. The minor of this proposition is proved, by the air being only warm while it is affected by the rays of the sun, and by its being found, that whenever that influence is withdrawn, it becomes cold again, and that it is by so much the more cold, in proportion to the absence of that influence. From whence it is observable, that in the temperate zones, the air is coldest when the nights are long; and that in the sub-polar, and circum-polar ones, it is extremely cold, on account of the influence of the sun being withdrawn from them for the space of six months together; and that when it returns to enlighten them, because of the obliquity of its rays, it still continues cold, far beyond the degree of mediocrity.