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this Book under Your Pa

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tronage, with great Humility and Thankfulness I lay it at your Feet ; not doubting but that (whatever my Performance is) the Subject will be acceptable, it being a Vindication of the Existence and Attributes of that Infinite BEING, to whom Your Royal Highness hath no less piously than juftly ascribed your great Royal FATHER's and Your Family's peaceable Accession to the Crown and Dignity of these Realms.

THAT

That the Blessings of the fame most merciful BEING may be perpetuated to Your Royal Highness and all Yours, is the hearty Prayer of,

Most Illustrious SIR,

Your Royal Highness's

Most Humble

Obedient Servant,

W. Derban.

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Otwithstanding that a Book is more compleat and valuable by Additions and

Amendments, yet I think that

many and great Additions are an Hardship and Injustice to the Purchasers of a former Edition; and therefore have in this, and in the foregoing Editions, avoided it as much as well I could, although some of my learned Friends would have persuaded me to it, and also contributed their Observations.

But

But yet from what I have said in the Preliminary Difc. p. 3. it will, I doubt not, be expeeted, that I should give

some account of the Observations, which the long and good Glasses in my Hands have afforded me since the laft Edition of this Book.

But I have little to boast of bere, having (besides the old former Complaint of the want of a long Pole to manage Mr. Huygens's Glass with) many great Hindrances in my Observations, partly by a very dangerous Fit of Sickness, which hung long about me; and partly by my necessary Affairs calling me to matters of another nature. But some of the most considerable of my Observations were these.

1. Viewing Venus with Mr. Huygens's Glass divers Nights, when near her Perigee, and much horned, I thought I saw Anfractus, or Rough

nesses

A 4

neffes on the concave Part of the enlighten’d Edge (such as we see in the New Moon) which I have represented as nearly as I could in Fig. 1 2.

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2. In my frequent Views of Jupiter, I find bis Belts to have great Variations; that they change their Places; that their Breadths alter, being sometimes broader, fometimes confiderably narrower; that sometimes they are more in Number, sometimes fewer; sometimes they are darker and blacker, sometimes thin and only like a Mif. Towards the Poles of Jupiter are the greatest Alterations, therė being sometimes

few or no Belts toward one or the other Pole; Sometimes one quite across the Polar Parts, another reaching but half, or a Part of the Way. . And even about the middle, or Equatorial Parts of Jupiter, where there are always Belts (and commonly two) yet these vary confide

rably.

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