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A great many such inflances might be added, if I thought it worth while, or, that any one would search after me to see whether things are so or not. But I shall content myself with observing, in the general, that Mr Johnjon has snitated the Socinians in indulging a trifling criticism with the holy scriptures and the writings of the fathers, which plays upon words, and hunts after all posible significations in order to find out a meaning that may be agreeable to his darling hypothesis, which he was obitinately resolved to defend, or, in the words of Origen, which he wrested and inisapplied to his bread-facrifice, to hold falt as long as he lived. But he did not know the scriptures, nor understand his own church.catechism.

SIR,

September 10th, 1744. If the following observations, &c. onll not take up too much

room in your Magazine, you will by inserting them tberein oblige (among others) your constant reader,

And humble servant,

EXONIENSIS. Observations on Mr Smith's Hypothefis concerning the

Tails of Comets.
WHIS author in p. 42 of his late Treatise of Comets, printed for y.
T

Robinson, endeavours to account for the singular position of their tails, regarding unexceptionably one quarter, by fupposing that phænomenon to be occasioned by the lucid vapours (with which the atmospheres of comets abound) becoming visible to us orly in the cornic and penumbral shadow of the comet: That this is not the sole cause fat lealt) of such an appearance, will, I presume, evidently appear from what follows. For,

1. If it were fo, the tail would always appcar, cæteris paribus, longeit when the comet is at the greatest distance from the sun, and shortest when rear him, which is contrary to experience.

2. The tail would appear exactly of the same size at the same distance from the sun, whether in the comei's dccent or ascent: but it has been observ’d that comes in their ascent from the sun have much larger and longer tails than when at the same distances from him in their decent.

If it be said that this is occafioned by the luminous vapors becoming more visible after the perihelion, on account of the greater quantity of them emitted from the comet when it has required fuch an intense heat as it must then have; I answer, tho' this may cause the tail to appear bizger, by increasing the splendor of the penumbra, it cannot make it appear of a greater length; for how high toever these vapours may aicend from the nucleus of the comet, they will, according to our author's hypothesis, be only visible in the conic and penumbral hadoiv, all their other parts being loft and extinguished in the fuperior luftre of the sun.

3. If this hypothefis were true, the tails of comets would never de. viate in the leali from their oppctition to the fun, but the vertex of the cone would always be as directly ofpolice to him as those parts thereof

which

Mr Smith's hypothesis of tails of comets examin’d. 231 which are nearest the nucleus : but on the contrary it has been observed in several comers, and particularly in the last, that the upper part of the tail inclined towards the parts which the comet had left by its motion. Ms S. to remove this difficaliy, would have it that the tail appeared fenfibly bent only when the coinet approach'd the horizon, which, he says,

was occasioned entirely by the refraction of the air, by which the • comci's body appeared to be elevated above the horizon, when it was • actually set, and the different parts of its tail, according to their eleva• tion, undergoing different degrees of refraction beni it into the form of • a curve, fuch as it seem'd to be.'. -To this it may be answer'd, that the tail of the late comet appeared (almost if not quite) as much bent when the comet was 10 or 15 degrees above the horizon, as when it was just fetting: but fupposing it true that it appear'd so only when near the horizon, yet even in this case I can't conceive that it could acquire any apparent curvature by the laws of refraction, but that it would only make a fomewhat more oblique angle with the horizon, and appear a very little shorter than when farther above it, and this variation of its apparent from its real position is so trifling, that 'tis scarce worth our notice. For supposing the come to be actually on the horizon, its tail extending 20°. in length, and making such an angle with the horizon, as that the altitude of the upper part of the tail should be but 14°. and consequently the middle part thereof about 7°. or 7o. 30'; then the comet itself, according to Tycho's table, would appear but 30' above the horizon, the middle of the tail 8'15" above its real altitude, and the upper part thereof but 8' 30", and nearly proportionable in the intermediate parts thereof: If this be duly considered, it will from hence plainly appcar that if there should be any curvature by means of the refraction, it would be altogether imperceptible, not sensibly varying from a straight line. I have here suppo'd the tail to make an oblique angle with the horizon, because, if it made a right angle therewith, 'tis beyond all difpute that the refraction could not then occasion any apparent curvature.

I am aware that this bent of the tail inay be plausibly (tho' not satisfactorily) accounted for on our author's hypothesis, by fuppofing the upper parts thereof generally at a greater distance from the earth, than thole parts which are contiguous to the nucleus; for it being now pait dispute that the motion of light is liicccfive and not instantanecus, the says coming from the luminous vapours in the upper part of the tail require longer time to reach the eye of the observer than those which come from the parts of the tail nearest the comet, and consequently the comet and parts of the tail contiguous thereto, must appear som what farther on in their course than the upper parts of the tail, which will therefore seem to incline, or bend backwards. I confess, were the above objection concerning the curvature of the tail, the only one that could be made to his hypothelis, I should not think it much weakened thereby, but that considering the progreflive motion of light) the great distance of the upper part of the tail might probably be the cause of such an appearance : but if the tails of comeis be really lo vastly extended as that the distances of their upper paris mcalured from the earth, exceed the distances of the comets chemelves and the lower parts of their tails, so very much, as 10 make them appear fo remarkably bent ; I say, it this be really the case, (which will admit of some doubt, and be liable to the same

kind

kind of objections as the arguments deduced from the refraction of light) it will as well account for (or at least help to confirm) Sir Isaac Newton's hypothesis, who thinks the appearance of the tails owing to steams and va.

pours exhald from the body, and gross atmosphere of comets, and ascending perpendicularly ; but afligns a different cause for this curvature, viz. the fame that causes the smoke of a burning coal in motion to ascend obBiquely, inclining from the motion of the coal. Now why may not this apparent bent of the tails of comets be partly caus’d by the very great distance of the upper part of their tails from the earth (occasioning the light reflected from thence to be longer in coming down than from the lower parts near the nucleus) tho'chiefly by the morion of the comet, which Îninders the perpendicular ascent of the steams and vapours which compose the tail ? And it both.concur to cause this appearance, the only thing that I apprehend can be said in favour of Mr Smith's hypothesis, will be as strong, if not a stronger argument in favour of Sir Isaac Newton's, which having other proofs to confirm it, of which Mr Smith's is deftitute, the former may more safely be adhered to, at least till another less liable to exceptions fhall be discovered.

Soone farther considerations relating to the Cyclopædia, ac

cafioned by a Plar and Specimen beretofore proposed ; communicated to the editor of the Miscellaneous Correspondence.

SIR, W

THEN I first met with your Magazine for Sept. 1744, and there

in viewed the contents of the 3d number of your Miscellaneous Corrispondence, perceiving there was something in it relpecting Mr Chambers's Cyclopedia, and the designed Supplement, I immediately determined to have all the three numbers of the above pamphlet, and gave an order for them accordingly.

The following particulars were laid together, immediately upon considering what appeared in the aforelaid 3d number of your pamphle:, under the title of Miscellaneous Correspondence ; but thrown by, as I was wilJing to see what remarks might be made by others. With the utmost diligence on my part, I have but just now obtained a fight of the 4th number, several orders being successively given by my bookseller in the country, before he could have it down. And now, Sir, finding less in your laft Miscellany relating to the Cyclopedia than I expected, it has put me upon troubling you with my thoughts hereupon, with which you may use your pleasure.

Tiine, with your own observations and experience will most fully con. firm or confute what I am going to say ;- but I am apt to believe while you have any thing material to propose and publish concerning the above great work, either respecting the improvement of what is already done, or any additions thereunto, you will have a sufficient call for your pamphler, and oblige your readers at the same time, I sincerely thank you *d your ingenious correspondents for what has been made public in the

two

two folio Sheets ; and it is hoped, both they and others will furnishi you with more, alike deserving of public regard.

I join with the ingenious author of the Plan and Specimen, in a firm belief that the Cyclopædia is the best colle&tion by far of any of the kind ; -I join with him also in respects to the worthy proprietors of that weighty work; nor am I less sensible of, or less concerned at, the ill attempts which have been made to plunder and pirate this, their lawful property : but for the comfort of these proprietors I may say, they are as yet very secure, since the imitations of the Cyclopædia are no less absurd, than the imitators are dishonest.

But though we gratefully remember the deceased Mr Chambers, and give to his work (already published) its due praise, we must yet acknowledge, with all its excellencies it hach its deficiencies, and will admit of many amendments. Indeed we can never rationally expect a work of this kind should be compleat and perfect; but ftill, the nearer perfection is arrived at, the better; and it is pity any reasonable pains or expence should be spared that might conduce hereunto. It is acknowledged a weighty undertaking; but it is yet hoped the proprietors will not shrink at it, since they may be assured their work will meet with the readiest reception. May I here with modefty add,-should it please his facret majesty king George the second to patronize and promote the completiore and publication of this extensively useful and excellent work, it would be far from being accounted among the least of those royal favours, which the king has conferred upon his subjects :-And if I might be allowed from what I know of myself, to speak for others, this generous act would bappily tend yet farther to endear his majelty to a considerable part of his subjects

, and such a part too as are capable (in some respects) of ferve ing his majesty and the present royal family, beyond many others.

I should greatly rejoice to see the whole body of the Cyclopædia published agreeable to the proposed Plan, or any inprovement of that Plan, fuppofing it be capable of any. As is now stands, I highly approve of the directions and differences proposed, particularly the nambering the paragraphs at the end, -indenting them (or the reverse) at the beginning, - judicious arrangement of the articles -he proposed use of Italia, with the fender use of capitals, &r. In Mort, the Plan seems to me the product of thought, the Specimen is ingenious and judicious,--ant the supplemental articles exceeding good, and are well digetted and drawn up. With this general approbation I could with pleasure take leave of this public-spirited gentleman and his generous performance ;--but whe! I consider the thing in view is not of a personal or private nature, and that what this writer has published, was done with design that it should be scanned and maturely contidered by others;--allo, that more than a litile may depend upon faithfulness and freedom upon this occasion, &r. it is hoped he will not suppose any of the following remarks proceed from z {pirit delighting in contradiction, or pleated with opposition any fara ther than right, truth, and publick welfare may seem icme way concerraum ed iherein.

There is no question but that a part of the beauty and excellency of such a work, as a dictionary of arts and sciences is, coes confit in the due arrangement of the materials, and placing them under the most proper beads ; (as in the Plan, Par. 61b, wiih she notes depending :) and belure,

fone

some proper rules adhered to, may be of general use to direct the difposal of the materials throughout the work: but it is a doubt with me, whether this can ever be done to the full satisfaction of every reader, as all are not equal judges, and yet every one will here judge for himself. Perhaps, also, this gentleman himself is not quite clear as to this particular, since in Par. 7th of his plan, he says, that accidental points in perspective, and accidental dignities in astronomy, ought to have been considered under the heads of point and dignity ;---and yet, if I understand him in Par. 10th, he seems to intimate, that point, as it relates to astronomy, ought to be explained under astronomy; and then, consequently point in peripective, under perspective, &c. I could with that this matter might be suitably attended to ; yet I conceive there is not a great deal depends upon it, since if the author herein has done wrong,

his references set me right. As to the sparing use of capitals, and shorter ways of reference, I like them in the main very well, as taking up less room; for I love to see a good book printed upon a good paper, and the same well filled; and I am very sure there will need no artful contrivances of any fort, to fwell the work; for, though I would not with that any thing should be admitted into it which might seem heavy and tedious to a judicious reader,---nothing but the cream and quintessence of what has been wrote upon the several subjects by. the best writers ;---yet, of these choice materials there is good store, only it will require some consider. able pains to collect then, unless, (as I would hope) it be in good part done already. But palling this, I could almoit petition for the use of capitals for a few words more than this gentleman teems willing to allow them to ; particularly for the words God, Lord, and Spirit, where this last does intend the divine spirit. This I find has been noticed by others : I shall therefore only observe, - according to my notion hereof, God, Lord, and Spirit, may be considered ur:der the class of proper names, and upon that footing, consistent with the gentleman's own Icheme and cuilom, each may lay claim to an initial capital, as well as any other of that class.

I like the proposed specimen (in the general) extremely well; fuch a marshalling of the materials in their respective articles would be of singular service to the whole. Almost every disease incident to the human beings may be illustrated under some or all of the following subdivisions, distinguifhed by Italics, viz. Name, Nature, Causes, Kindi, Cafes, Prevention, Cure. The gentleman indeed does not so well approve of these logical terms; and it is manifest from his specimen, we. may

do

very well without any direct use of them; and yet, (for the fake of variety) I think we may not disagreeably make nearer approaches to them. (V. the article ANEURISM h reunto annexed). And as to other articles, (especially if any thing large) they may be thrown under certain divisions, somewhat analogous to those before mentioned, according to the nature and matter of the articles themselves.

It it certainly belt chat each article Mould be considered together, and not divided among fynonymal words :---feless repetitions are hereby avoided, and the reader has what he wants at one view : But, then, every synonymal word ought carefully (though barely) to be inserted in its proper place, and each one have a reference annered to

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