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Their periodical Tit. 9′. 224a. 16h. 49′ 187a. 23h. 16'.

Their daily mean 1 08′′. 01°. 36′. 08′′. 104°. 05′. 32′′.

The Planets inhabited.

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and, because they have also observed several dark Spots on the Disk of Jupiter, they conclude his Surface is divided into Land and Water, as that of our Globe is, and is therefore inhabited; as they also suppose all other Planets are.

A. Then they imagine the Planets to be fo many Earths, or peopled Worlds? But do not the different Diftances of the Planets render that impoffible, by occafioning too great Light and Heat in fome, and too great Cold and Darkness in others?

B. Their Bodies, with their feveral Organs of Senfe, are undoubtedly fuited and adapted to the different Conftitutions and Temperaments of the Planets, which are the Extremes, by the fame almighty Power, and all-wife Providence, which hath fuited our Bodies, &c. to the State of this Planet we live on, which is the mean.

A. What are the different Dimenfions, Revolutions, Denfities, Quantities of Matter, Light, Heat, &c. of the fix primary Planets, we are difcourfing of?

B. These will be all feen to the best Advantage, and compared in one general View; to that End I have drawn up a Synopfis of them all together, as you here fee, all grounded on Mr. Whifton's Calculations, which are the moft moderate of any: I have moreover drawn the fix primary Pla

nets in their true Proportions of Magnitude in Fig. XXV.

A. Sir, 'Tis very good; I take it as a great Favour, and humbly thank you.

CHAP. V.

Of Cometography, or the Philofophy of the Comets.

A.

H

Aving thus pretty largely converfed with the Planets, and viewed their various Natures, Numbers, and Affections; let us next, if you please, difcourfe of the Comets: And, in the firft Place, pray tell me what the proper Meaning of the Word Comet is?

B. Comet is a Greek Word, derived of the Verb Kouaw, to have long Locks, or wear long dishevelled Hair; because a Comet feems to have as it were a long hairy Tail.

A. Pray what is the Matter or Substance of a Comet?

B. Sir Ifaac Newton faith the Bodies of Comets, or blazing Stars, are solid, compact, fixed, and durable Subftances; and

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are,

Of the Comets, their Motion, &c. 131 are, indeed, but a different Kind of Planets, which move about the Sun, and shine by the Light of the Sun-Beams reflected from them.

A. Pray how many Kinds of Comets are there?

B. Comets receive a Divifion or Distinction on account of the different Form of their Tails: Thus,

Cometa Crinita, having a long Tail like a Horfe's.

Cometa Barbata, having a Tail like a long Beard.

Cometa Enfiformis, having a Tail like a Sword.

A. Why, Sir, do the Comets appear with blazing Tails, and no other Planet or Star do fo?

B. This feems owing to fome peculiar unctuous Matter in the Bodies of the Comets; which by their Approach to the Sun's Body is prodigiously heated, rarified, and made to fly off in a fiery Vapour, on that Side oppofite to the Sun, in the Form of a long Tail, growing wider and thinner (as all fumy Vapours do) the farther it proceeds from the Comet's Body.

A. Then you fuppofe, I find, that the Comets revolve about the Sun, as well as the