[] That the heavenly Bodies move round their own Axes, is, beyond all doubt, manifest to our Eye, in some of them, from the Spots visible on them. The Spots on the Sun (easily visible with an ordinary Glass) do manifest him to revolve round his own Axis in about 25¼ Days. The Spots on ♃ and ♂ prove those two Planets to revolve also from East to West, as Dr. Hook discover’d in 1664, and 1665. And ♀ also (although near the strong Rays of the Sun) hath, from some Spots, been discovered by Mr. Cassini, in 1666, and 1667, to have a manifest Rotation. V. Lowth. Abridg. Vol. 1. p. 382, and 423, 425. And such Uniformity hath the Creator observ’d in the Works of Nature, that what is observable in one, is generally to be found in all others of the same kind. So that since ’tis manifest the Sun, and three of his Planets whirl round, it is very reasonable to conclude all the rest do so too, yea, every Globe of the Universe.
[c] The Earth’s Circumference being 25031½ Miles, (according to [Book II. Chap. 2. Note (a).]) if we divide that into 24 Hours, we shall find the Motion of the Earth to be nearly 1043 Miles in an Hour. Which, by the by, is a far more reasonable and less rapid Rate, than that of the Sun would be, if we suppose the Earth to stand still, and the Sun to move round the Earth. For according to the Proportions in [Note (e)], of the preceding Chapter, the Circumference of the Magnus Orbis is 540686225 English Miles, which divided by 24 Hours, gives 22528364 Miles in an Hour. But what is this to the Rapidity of the fixt Stars, if we suppose them; not the Earth, to move? Which is a good Argument for the Earth’s Motion.
[d] Nihil majus, quàm quòd ita stabilis est Mundus, atque ita cohæret ad permanendum, ut nihil nè excogitari quidem possit aptius. Omnes enim partes ejus undique medium locum capessentes, nituntur æqualiter: maximè autem corpora inter se juncta permanent, cum quodam quasi vinculo circumdata colligantur: quod facit ea natura, quæ per omnem mundum omnia Mente, & Ratione conficiens, funditur, & ad medium rapit, & convertit extrema, Cic. de Nat. Deor. l. 2. c. 45.
[e] Eâdem ratione Mare, cùm supra terram sit, medium tamen terræ locum expetens, conglobatur undique æqualiter, neque redundat unquam, neque effunditur. Id. paulo post.
[f] That there is no such Thing as positive Levity, but that Levity is only a less Gravity, is abundantly manifested by the acute Seig. Alph. Borelli de Mot. à Grav. pend. cap. 4. See also the Annotations of the learned and ingenious Dr. Clark on Rohaulti Phys. p. 1. c. 16. Note 3. Also the Exper. of the Acad. del Cimento, p. 118, &c. Dr. Wallis’s Disc. of Gravity and Gravitation before the Royal Society, Nov. 12. 1674. p. 28, &c.
[g] I have before in [Note (a), Chap. 3.] shewn what Vapours are, and how they are rais’d. That which I shall here note, is their Quantity: Concerning which the before-commended Dr. Halley hath given us some curious Experiments in our Phil. Transact. which may be met with together in Mr. Lowthorp’s Abridg. Vol. II. p. 108. and 126. Mr. Sedileau also at Paris observed it for near three Years. By all their Observations it appears, that in the Winter Months the Evaporations are least, and greatest in Summer, and most of all in windy Weather. And by Monsieur Sedileau’s Observations it appears, that what is raised in Vapours, exceeds that which falleth in Rain. In the seven last Months of the Year 1688, the Evaporations amounted to 22 Inches 5 Lines; but the Rain only to Inches 6⅓ Lines: In 1689, the Evaporations were 32 Inches 10½ Lines; but the Rain 18 Inches 1 Line: In 1690, the Evaporations 30 Inches 11 Lines; the Rain 21 Inches ⅓ of a Line. Vid. Mem. de Math. Phys. Ann. 1692. p. 25.
If it be demanded, What becomes of the Overplus of Exhalations that descend not in Rain? I answer, They are partly tumbled down and spent by the Winds, and partly descend in Dews, which amount to a greater quantity than is commonly imagined. Dr. Halley found the descent of Vapours in Dews so prodigious at St. Helena, that he makes no doubt to attribute the Origine of Fountains thereto. And I my self have seen in a still, cool Evening, large thick Clouds hanging, without any Motion in the Air, which in two or three Hours Time have been melted down by Degrees, by the cold of the Evening, so that not any the least Remains of them have been left.
[h] See [Book II. Chap. 3. Note (c).]
