" he might affure all those who believe in, and die to him, that they fhall never be detained ❝ there.

The foregoing Citations are in the very Words of our Author, that the Reader might form an exact Idea of his Performance, which has in it nothing better than what I have here prefented him. I have given him the Articles entire, (excepting a few Paffages that have been drop'd for Brevity fake, where he meets a Break, and which contributed no way to the Perfection of the Difcourfe,) that he might have compleat Effays on two important Doctrines of Chriftianity, as well as an Opportunity of discovering the Value of this Expofition of the Chriftian Faith, in general.

The Elements of Sir Ifaac Newton's Philofophy by Mr. VOLTAIRE. Tranflated from the French. Revised and corrected by JOHN HANNA, M. A. With Explication of fome Words in Alphabetical Order. Printed for Stephen Auften, at the Angel and Bible in St. Paul's Church-yard. 1738. Octavo. Pages 363, befides Cuts, &c.

T

HOSE who are acquainted with the Genius of Mr. Voltaire, know what they are to expect from him upon a Subject of this Nature. It was his Defign (as we learn from his Tranflator)

to give only a Taste of Sir Ifaac Newton's Na"tural Philofophy, to those who have heard his "Works much commended, but had not enough "of Mathematical Learning to read them; tho'

"there'

"there are in feveral Places feveral curious Things "to entertain the more Learned. " The Work is divided into twenty-five Chapters; fourteen of which may be termed Optical: the Doctrine of Light and Colours is handled in them. Our Author therein fhews the Nature of Light, and the Manner of its coming to us: He explains, as well as he is able, that Property which it has of reflecting itself, and makes it appear, that it is not reflected by the folid Parts of Bodies, as vulgarly believed: He paffes from this to another Property we perceive in it, of refracting in paffing from one Substance into another, and of taking a new Course in its Progreffion: He then defcribes the Structure and Mechanism of the Eye; and the Modus of Vifion: This leads him to fpeak of Concave and Convex Glaffes, to fhew how they affift the Organ, and rectify the Sight, and to affign the Reafon of dioptrical and catroptical Phenomena: He then demonstrates the Infufficiency of the common Theory of Vision to account for our Conceptions of the Diftances, Magnitudes, Figures, and Situation of Bodies: In the next Place he establishes the Cause of the Refraction of the Rays of Light in paffing from one Medium to another; evincing this Caufe to be a general Law of Nature unknown before Newton; and that the Inflection of Light is also an Effect of it: Thefe general Principles are followed by a great Variety of Illuftrations, which are fo many Confirmations of them: Among the Phenomena that are folved, we may be fure of finding the Rainbow; it is infifted on copioufly: The Investigation of the Caufe of Refrangibility affords our Author a Proof of the Exiftence of Atoms, or indivifible Bodies in Nature; and he fhews the fimple Particles of Light to be fuch: In the last Place, under the general Head of Opticks, he expatiates on the surprising Analogy there is between P 2

Light

Light and Sound, the Refemblance there is found between the feven primitive Colours and the feven Notes in Mufick.

In the fifteenth Chapter; after feveral introductory Propofitions concerning Gravity and the Laws of Attraction, Mr. Voltaire begins to attack Defcartes's Syftem of the Univerfe, and maintains, that his Opinion of a fubtil Matter, Vortices, and a Plenitude, ought to be rejected. In the fixteenth Chapter he demonstrates the two laft, viz. the Vortices and Plenum to be impoffible, and confequently that that Philofopher's Hypothefis with relation to the Caufe of Gravity is merely imaginary. In the enfuing Chapter the Nature of Vacuity and Space is defined and fettled, and fome Objections against a Void are propofed and answered. The true Laws of Gravitation are entered upon in the eighteenth Chapter; they are adjusted by the Experiments and Obfervations of Galileo and Newton, and they are employ'd for determining feveral Particularities concerning the Moon's Orbit. In the nineteenth and three following Chapters, the Laws and Effects of Gravitation in the Solar System are farther exhibited and explicated; Kepler is celebrated on Account of his admirable Discovery of the Law which the Planets univerfally obey in their Revolutions, while his Notion concerning the Ground and Reafon of it is exposed and ridiculed : This Law is fhewn to infer Sir Ifaac Newton's Principles with regard to Gravitation, and to determine, in the affirmative, the Question of the Earth's annual Motion.

In the twenty-third Chapter our Author has framed a Theory of our Planetary World, from the Discoveries of Sir Ifaac Newton. The Sun is the first Thing he prefents us with, and he proves, that the central Point towards which all the Parts of our System gravitate, is, neceffarily, in the Body

of

of that Luminary, tho' not precisely in the Middle of it. The mutual Influences of that prodigious Globe and the incircling Planets are computed; as are also its Magnitude, its Denfity, and the Degree of Gravitation on its Surface. The Planets appear afterwards: Their Distance from the Sun, their Density, their folid Quantity, and attractive Force, are feverally estimated; and the most remarkable Phenomena of them are minutely defcribed.

The Account of our Earth is diftinguished by a Digreffion, concerning a Period, relating thereto, of 1,944,000 Years newly difcovered. The Reader will be entertained with that Difcourfe prefently, wherein he will find a Subject of fufficient Dignity and Beauty in itself, glittering with Mr. Voltaire's ufual Erudition and Eloquence. This Character is more or lefs applicable to the greateft Part of this Treatife; the Caft of which is adapted to the Temper of those, for whofe Perufal it was originally defigned. The English Tafte, especially with refpect to Points of Mathematicks and natural Science, is rather too grave and folemn, to relifh the Stile and Air in which Mr. Voltaire chufes to handle them. His Diction is generally fuch, as would better become an Effay on fome brilliant Topic of what we commonly call the Belles Lettres; he quotes Perfons and Facts with extraordinary Applause or Admiration, and almost every Paragraph is diftinguished by fome fort of Embroidery. Howeyer, after all, thefe Circumftances, tho' they fomewhat depreciate, are far from utterly invalidating the Merit of this Performance, wherein many fublime Truths are more effectually reduced to vulgar Understandings, than in fome other Explications of Sir Ifaac Newton's Philofophy.

In the twenty-fourth Chapter our Author treats of the Zodiacal Light, the Comets, and the fixed Stars. P 3

The

The principal Reafon for which he at all mentions the Zodiacal Light, is, to clear up an Objection, which it seems to reflect on a Demonftration of Sir Ifaac's, concerning the Motion of Bodies in refifting Mediums. After a very minute Defcription of this Phenomenon, he is fo happy as to remove all the Difficulty relating thereto, by means of an Idea for which he acknowledges himself obliged to the celebrated Facio de Duilliers: There is a good deal of Singularity in this Solution.

*

Mr. Voltaire has put together the Opinions of feveral Philofophers concerning the Orbits, the Atmospheres, and Tails of Comets. Thefe Collections confer very little Inftruction, and only fhew us the great Diversity of Sentiment there may be among the most learned Men upon the fame Subject.

At the Entrance of the Article of the fixed Stars, he encounters another feeming Contradiction of the Newtonian Syftem, with regard to thofe Bodies. When he has fettled that Affair, to the Honour of Sir Ifaac, he refutes Mr. Wolf's fantaftical Solution of the Occultation and periodical Returns of certain Stars, which have appeared a mong the fixed ones, and have been reputed of their Number. A few Inferences that he draws from his Arguments (as he calls them) upon these Heads, are the Conclufion of this Chapter.

The twenty-fifth (and laft) Chapter may be confidered as a Sequel of the twenty-firft, wherein

*This Gentleman made a confiderable Figure in the learned World, by his great Skill in the nobleft Branches of Mathematicks, before his unhappy Delufion by that pretended Spirit of Prophecy, which infatuated and ruined fo many Perions of Worth, about the Beginning of this Century; fince which Time his Character has been very much eclipfed in the Republick of Letters within these two Years he has again diftinguished himfelf by fome peculiar Aftronomical Notions, and by fome Propofals for publishing an English Verfion of the poetical Books of the Hebrew Bible, and discovering the true Laws of that Poetry."

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