from excluded the Air only, for the most part, that Faculty, notwithstanding that that alfo in itself is visible like other Bodies, and feems to be very well adapted thereto by its Elaftical and other Properties, as appears when we comprefs a great Quantity of Air in the Pump, and then fuddenly let it out again by the Cock? Now let an Atheist ask himself, whether this can appear to him to be fo order'd without any Defign or Purpofe? And fince the Air itself being thus vifible, and fo far capable of stopping the Course of Light, would caufe us to live as it were in a continual Fog, and hinder us from seeing conveniently moft of the Objects about us, whether he does not obferve, that this fame adorable Wisdom does here interpose after a wonderful Manner for the Benefit of Mankind? SECT. XXXVI. The Wonders of Reflection. AND to the end that many miferable Philofophers, who think they understand so well the Laws of Reflections and Refractions, fhould not imagine that there are not more Wonders concealed in the fame, and that their Understanding. does perfectly extend itself thereto, let them give a fatisfactory Reason of the Appearances mention'd by that accurate Philofopher Sir Isaac Newton, in his Opticks, p. 238, and 346, laft Edition; and tell us what is the Caufe that the Light paffing from a Glass, and falling with a certain Obliquity upon a Place from which the Air has been exhaufted, does not proceed on,but returns back again to the Glafs and that when the Rays fall from the Glafs upon the Air with an Oblique Angle of more than 40 or 41 Degrees, the fame are likewife entirely reflected; whereas if they fall with ą leffer Obliquity, moft of 'em will pass thro' the Bbb 3 ز Air, Air, fo that the Light which paffing thro' the Air upon the Glafs, can make itfelf a way thro' the fame, and yet the Light that paffes from the Glafs to the Air in the fame Obliquity feems unable to make itself a Paffage in a fo much thinner Matter, whereby to purfue its Course. They that have a mind to fee many wonderful Circumftances befides thefe, may confult the above-mention'd Places, and from the Experiments there related, may with Certainty enough infer, that we do not rightly understand the Nature of Light, with respect to its Reflections, whilft we only confider it as a Globe or Ball rebounding from any hard Matter. At least it is evident hereby, that there are Laws in Nature to which the Light is fubjected, of which perhaps none of the Naturalifts, if they had not thus found them true by Experience, would ever have thought. SECE. XXXVII. Experiments fhewing that Light may become a Solid Body. I MIGHT have here forborn to have enquired into certain Questions propofed by Sir Ifaac New ton, in his Opticks, p. 349. Quaft. XXX. where that Gentleman feems to incline to the Opinion, that Light, befides its being the moft active Matter in Nature, may likewife become the Subftance of palpable Things, and be converted into a folid Body; but fince Mr. Homberg has put this Affair out of doubt by feveral Experiments recited in the Memoirs of the Royal French Academy, 1705. p. 122, c. it feems not improper to fhew here likewife this Ufe of Light. And, Firft, That Light penetrates almost all Bodies, even those that appear obfcure to the Eye, and paffes thro' the fame, as is fufficiently known to fuch as make ufe of good Microfcopes, fince almost every Object that has been viewed therewith, provided they are but thin enough, do in fome manner become tranfparent. The faid Sir Ifaac Newton tells us in his Opticks, P. 223. That he has obferved the fame in a dark Chamber, when any Matter reduced to a proper Thinnefs, was placed before the Hole through which the Light would otherwife have paffed; and he only excepts white metalick Bodies, which seem to reflect all the Light falling on them. Secondly, If we fuppofe Flame to confit for the moft part of Light, we fee that it turns to a folid Body in the burning of Chalk, and especially in the making of Minium or Red-Lead from Lead-Afhes, which after having burnt and glow'd a great while, become more heavy. Mr. Homberg likewife relates, that if Quickfilver, being reduc'd to the utmoft Fluidity by Steel and Antimony, be put over a Fire in a Glafs, the parts of the Fire which penetrate it thro' the Glafs, and which may therefore be deemed a Light without any additional Mixture, will change it into a Powder heavier than the Quickfilver was at firft, and be of fuch Proof againft Fire, that it will bear glowing at least 24 Hours without any Evaporation; and when driven with a very violent Fire, it may indeed evaporate into Smoak, but will however leave a little Parcel of itself behind, which being formed by this Light in the Quickfilver, will affume the Qualities of a folid and malleable Metal: This may be farther confirmed by the Experiments made on the like Occafion by Mr. Boyle, by which he fhews how fome Bodies, fhut up on every Side in Glafs, b:come Bbb 4 more more ponderous by the Fire or Light that paffes thro' the Pores of the faid Glass; but this is proved yet more plainly, and beyond all Difpute, by the following Experiment of the faid Mr. Homberg in the above-mention'd Place, who having reduced four Ounces of Regulus Martis to Powder, placed it about the Distance of 1 Foot from the true Focus of the Burning-Glass of the Duke of Orleans, ftirring it about from time to time with an Iron Spoon; by the Heat of this Light there afcended a great Smoak from the faid Regulus for the space of an Hour, and then it ceased: And tho' one might expect, that by the lofs of all thofe Particles which evaporated in Smoak, the Weight thereof would have been diminifhed; yet on the contrary, he found that the Weight of it was increafed 1 quarter of an Ounce, and fome Grains, that is to fay, about a tenth part of the whole. Afterwards he placed the fame in a greater Heat, or in the real Focus, which put the Regulus into Fufion, and then it weighed no more than 3 Ounces; fo that he reckons that this lofs of the half Ounce happening by the Evaporation and Smoaking, one may fafely affirm, that the Light had firft augmented it with almost the Weight of a whole Ounce, which by melting, and the Operation of fuch great Heat was diffpated again. Now whether this laft Calculation be juft or not, it plainly follows from hence, that this Regulus had in the firft of thofe Experiments gained by the Rays of Light, the Weight of almoft half an Ounce over and above all that evaporated in Smoak; which clearly fhews, that Light can conjoyn itself to folid and palpable Bodies, and increafe the Matter thereof. But the Reader is defired to confider this as the the firft Sketch of a new Discovery: And I fhall not endeavour any farther here to determine, whether we ought with thofe great Men abovemention'd, to confider Light as the chiefeft and most active Principle in Nature. This however seems to be unconteftably true, that Light is either a pure and uncompounded Fire, or carries fuch a Matter along with it; and how much ought to be ascribed to the A&tivity of Fire is fufficiently known to every one. Experience likewife teacheth us, how much all Plants and Animals depend upon the Influence of the Light of the Sun; infomuch, that if it cannot be faid to be the only active Principle in Nature, at least it may be certainly reckon'd among the chiefeft. SECT. XXXVIII. Optical Experiments passed over. I SHALL not amuse my self here to rehearse the common and known Experiments about Light, which the Science of Opticks fuggefts as fo many Wonders, tho' they furnifh us with one of the greatest Proofs to demonftrate, that there is a God who directs this miraculous Matter of Light, rendering it fubje&t to fuch Laws, notwithstanding the amazing Velocity of its Motions, that even the greatest Mathematicians muft ftand aftonifhed, when they fee all that true Argumentation can deduce from it, performed by the fame. Thus we fee when it falls upon the Superficies of a Looking-Glafs, that it paints the Object from whence it flows upon the faid Looking-Glass, where the Image is reprefented erect equally large, and at the fame Distance as the Object If it falls upon Spherical Convex-Glaffes, it likewife makes behind the fame a nearer and dire& Image upon the Glass; and upon Spherical Concave Glaffes the Image will be fome |