fometimes direct, fometimes inverted, now greater, then fmaller; one while it will appear before, another while behind the Glafs, which may be fhewn almoft by Refraction in fo many Changes thro' Convex and Concave Glaffes.

SECT. XXXIX. A Dark Chamber, and Convictions from thence.

Now if any Body would with fmall Expence try an Experiment about the Operations of Light, let him make what they call a Dark Chamber, of which mention has been already made in Contempl. XII. by which means he will fee upon a white Paper, or a piece of Linnen held in the Focus of the Glafs that is fix'd in the Window, the Pictures of every thing that is on the outside of the Chamber, which will produce a very pleafing Profpect, efpecially if the Chamber look'd upon a Flower-Garden; for then one might fee the Flowers in all their Colours, and Figures, painted upon the Paper, and their Motions occafion'd by the Wind; and if there be any Men or other Creatures in the Garden, it will be a natural Moving Picture.

SECT. XL. The Properties of the Rays of Light, with respect to Colours.

BUT before we take our leave of Light, we fhall add fomething which feems to furpass even Wonder itself. Could any Body believe it, when he looks upon the bright and untinged Light of the Sun, that the fame can be divided and diftinguifhed into fo many different forts of tinged or dyed Rays, as the Great Creator has been pleafed to communicate of capital Colours or fimple Tin&tures,

Tin&ures, or as the Learned call them, Homogeneal Colours?

And yet Experience teaches the fame, as alfo that each of these coloured Rays fuffers a particular Quantity of Refraction, and that the white, or rather the clear Light, is thereby fplit into different Parts or Kinds of Rays, which appearing fingly, fhew a red, yellow, green, blew and purple Colour; on which account these Rays are named by Sir Isaac Newton, Red, Yellow, &c. each of 'em according to their particular Colours, forafmuch as they are natural to them, and cannot be altered by any fubfequent Refraction or Reflection.

Moreover, fince all unmix'd Rays of the Sun do represent a certain Colour, and the whole Subftance of Light confifts of the faid Rays, it seemed to be hardly poffible, but that all thefe Tin&ures jumbled together, muft occafion an Obfcurity to our Sight; forafmuch as Blue, Purple, Red, and other Rays, are far fhort of that Brightnefs which occurs to us in the pure Light of the Sun or Day; and yet we find that all these colour'd Rays that proceed from Light by Separation, being collected and mix'd with each other, do entirely lose their refpective Tin&ures, and together produce a clear and tranfparent Light in all things, like that untinged Light that comes down to us from the Sun: Which new conftituted Light may be again, as before, divided into its coloured Rays, which, if one will, being mix'd together again, fhall the fecond time represent an uncoloured Light clear and tranfparent; concerning all which, the firft Discoverer, Sir Ifaac Newton, has treated largely in his Opticks.

Now I ask an unhappy Atheist, whether he can believe that Iight has acquired these Properties

perties either by Chance or ignorant Causes? Or whether he muft not acknowledge, that those Men argue much more juftly, who conclude from hence, that the great and gracious Benefactor of Mankind has produced all these differently colour'd Rays, to the end that the Beholder may be fo much more agreeably affected and refreshed with the Sight of his Creatures; and that he has placed in them the laft Property, whereby all of 'em being mingled together do compose a clear and tranfparent Light, to the end that the obfcurity of the Colours may not embarrass Human Eyes?

Befides his Wifdom and Beneficence must be acknowledged herein, that in the Parts which compofe different colour'd Bodies, he has placed fuch a Difpofition, whereby one Body when this compounded Light falls upon it, is adapted to reflect only one, or fome particular kinds of Rays; for Inftance one only Red, another only Yellow, a third both of 'em equally, and no other (by which a kind of a Gold-colour between Red and Yellow is generated) I fay, to reflect these in a greater quantity, by which means each Body according to one or more forts of Rays which it reflects, either Simple or Compound, reprefents its particular Colour, and from thence is denominated Red, Yellow, &c.

How strange foever this Language might have been to all former Philofophers, yet the fame is at prefent put out of all doubt by the afore-quated Opticks of Sir Ifaac Newton; who tho' he may be juftly reckoned by every Body among the most famous Mathematicians of the World, yet to fet an Example to these less experienced Gentlemen, that they should not too much relie upon Conjectures and Hypothefes,has proved the fame to be unquestionably true, not by Demonftrations founded

founded upon Arguments, but by manifold and exceeding nice Experiments. Now those that have a mind to read and try the fame, may meet with 'em in the aforefaid Treatise of Opticks, efpecially in the First Book.

SECT. XLI. The Divifion of Light in InlandChrystal.

BESIDES the above-mentioned Divifions of Light, whereby it is fplit into various coloured Rays, Mr. Huygens in his Treatife about Light, p. 61. and Sir Ifaac Newton in his Opticks, Query 25. p. 328. do fhew us another Divifion or Splitting of Light, which it undergoes when it meets with Island-Chryftal; upon which as foon as a Ray of Light falls, it is divided into two other Rays that preferve however the fame Colour.

Of thefe Divifions or Splittings of the Subftance of Light into feveral other Parts, as well tinged in the first Cafe, as fimple or untinged in the second, I don't know that there was ever the leaft mention made, or Track to be found among the ancient Naturalifts; nor that this Matter has been put out of doubt fooner than in the last Age by accurate Inquiries and undeniable Experiments.

SECT. XLII. The Ufefulness of the Moon.

Now let the Reader return with us to Tab. XXI. Fig. 4. and fuppofe the Sun to be reprefented by A B, and the Earth by CD, in which Situation, as we have said before, the Shadow of the Earth, or the pyramidal Figure CPD makes the Night, it will not be then difficult for him to fancy the great Darkness with which thofe that dwell

dwell at T muft' be involved; forafmuch as not the least Ray of Light flowing from the Sun A B, can come to them directly, or in a straight Line.

Now if you will please to obferve, that the Moon M being oppofite to the Sun A B, is at Full to those that live at T, that is to fay, they fee its whole enlighten'd Side: You will tell us whether you can think there is any Gratitude in those People that fhall deny their great Obligations to him who has furnished them with this Light of the Moon in fuch their Darkness.

SECT. XLIII. Convictions from hence, and the Eclipfes.

Now the only Evafion that fuch People can make, is, that all this happens by Chance, or by neceffary Causes, and confequently that no Thankfulness is due: But if the Gracious Creator of the Moon had no Wisdom, nor the Benefit which Men enjoy from the Light thereof, is not to be reckoned one of his great Views and Defigns, how will they account for the following Particulars!

I. That the Light of the Sun has a Property when it falls upon any Bodies (as here from N, the Center of the Sun, upon M the Moon) to rebound back from it again, and to produce a reflected Ray MT; by which means those that would otherwife remain in the midft of the dark Cone CPD, are enlightned. Now, that without this Faculty of Light, there could be no Rays reflected from the Moon to our Earth, is plain enough.

II. Why is the Moon M, which is much fmaller than the Globe of the Earth, placed at no greater Distance from it; fo that (as we fee in Saturn, and other great Planets) its Breadth and

Diameter