"The following curious anecdote is told, in the Negaristan, of a famous lawyer of Baghdad, called Abu Jofeph. It marks feveral culiarities in the Mohanmedan law, and difplays fome cafuiftical ingenuity in adapting them to the views of his clients. The Khalif Haran Alrahid had taken a fancy for a female flave belonging to his brother Ibrahim. He offered to purchafe her; but Ibrahim, though willing to oblige his fovereign, had fworn, that he would neither fell nor give her away. As all parties wished to remove this difficulty, Abu Jofeph was confulted: who advised Ibrahim to give his brother one half of the flave, and to feli him the other. Happy to be relieved from this embarraffment, the Khalif ordered 300,000 dinars for the moiety of the flave: which Ibrahim, as a mark of his acknowledgement, immediately prefented to the lawyer. But a fecond difficulty now arofe. The Mollem law prohibits all commerce between a man and the wife or concubine of his brother, till fhe has been remarried and divorced by a third perfon. Abu Jofeph advised the Khalif to marry her to one of his flaves; who, for a proper confidera tion, would be easily induced to repudiate her on the spot. The ceremony was inftantly performed: but the flave, falling in love with his handfome fpoufe, could not be prevailed upon to confent to a feparation. Here was a ftrange and unexpected dilemma; for, all def potic as the Khalif was, he durft not compel him. But Abu Jofeph foon difcovered an expedient. He defired the Khalif to make a prefent to the lady of her new husband, which virtually diffolved the marriage; as no woman, by the Mohammedan law, can be the wife of her own flave. Overjoyed that the Gordian knot was thus fo ingenioufly unloofed, the Khalif gave him 10,000 dinars; and the fair lave receiving a confiderable prefent from her royal lover, prefented him with 10,000 more: fo that Abu Joseph, in a few hours, found his fees amount to 50,000 dinars, or nearly 15000 l."

With what propriety may we not congratulate ourselves, that, in thefe honeft times and in this free country, money is not to be made by fuch chicanery; and yet we have heard of a folicitor, who made near 70,0col. out of one good caufe, afflicted with a flow fever in chancery.-But to conclude, in juftice to Mr. Richardfon, in his own words.

"The subjects touched upon, in this Differtation, are various; and fome of them may be difcovered, perhaps, to have been too flightly confidered. I have differed freely from very high authorities; but, fenfible how much easier it is to point out errors than to avoid them, I -fubmit myself as freely to the decifion of every intelligent reader. Be it delivered with the temper of the gentleman and the fcholar, I fall be proud of every ingenious criticifin; and endeavour to improve by a difcovery of my faults. I am not attached to a fingle idea that may -be found inconfiftent with truth or propriety; and should, with far lefs pain, fee the most favourite theory fall before a judicious inveftigation, than be justly cenfured for a failure in candour or politenefs.

Obfer

Obfervations and Conjectures on the Nature and Properties of Light, and on the Theory of Comets. By William Cole. 8vo. 2S. Robinfon.

We have refumed the confideration of this pamphlet *, in confequence of our Editor's having received a letter from its Author; in which the latter complains of our not only having overlooked, mifunderstood, and mifreprefented his arguments, but of our having treated him on the whole ungenteely. To make him and our readers, therefore, all the amends in our power, we shall print his whole letter, with fuch illuftrative remarks as the occafion fuggefts.

To W. KENRICK, LL. D. Editor of the London Review.

"SIR,

"I TAKE the Liberty to addrefs you as the oftenfible Author of the Remarks upon my Pamphlet refpecting the nature and properties of Light, &c. in your last Review. Had you, Sir, been in any degree guided, in thote Remarks, by that impartiality which you owe to the Public, and of which you fail not to make the moft liberal profeflions, you would not have fubjected yourself to a direct call from the Author to justify the imperfect and prejudiced, not to fay ungentlemanly, account which you have given of that performance."

"

Aware of fuch precipitate imputations as the above, our Editor, long fince, repeatedly entered his caveat against them. He defires us, again, alfo, to repeat that he is the oftenfible editor only of the Review, and not the oftenfible author of any particular article contained in it. Had Mr. Cole civilly defired to know the writer of the article in queftion, he fhould have been directly informed. As to any thing ungentlemanly in it, if any thing fuch there be, it lies with us; who are really fo ungenteel as to be inconscious of giving, as we were far from meaning to give, any kind of offence. That we are really as impartial as we profefs, may be feen, in part, from that equal freedom of cenfure or approbation with which we treat all writers of what rank or ftation foever; knowing no refpe&t of perfons in the republic of letters.

"The obfervations on the Theory of Comets you have not thought worth the finalleft notice. Shall I beg the favour of you, Sir, to try your talent upon that Subject in your next Review. You will find there a certain note upon the vis incrtice, which will, I think, afford no bad exercile for your critico-philofophical abilities.

You have alfo entirely paffed over the principal matters in the Obfervations upon Light, and have touched only upon thofe few palfages which oppofe your own notions. And even here you have not thought proper to oder a fingle arguiment in fupport of your doctrine."

*See London Review for October.

That

That we paffed over Mr. Cole's Theory of Comets, is undoubtedly true; and our reafon for it was this. It appeared, though novel enough to deferve notice, too fanciful, and deftitute of support from obfervation, to afford ground of inveftigation. We now, however, muft do Mr. Cole the juftice to fay, that he fully confutes Mr. Brydone's objections to the commonly-received theory; and that, though we cannot directly give into his [Mr. Cole's] notion, that Comets are not permanent parts of the Solar System, for want of fufficient proof, that the irregularity of their return may not be owing to incidental attractions operating within that fyftem; we yet do not take upon us to fay that it is as chimerical as it is ingenious. We do not deny its poffibility, nay might admit its probability, did we adopt the generally-received opinion, viz. that the planetary bodies continue only the original motion. first arbitrarily given them by an abfolute projectile force. In our opinion, however, this is not the cafe; their magnitude, diftance, revolutions, both folar and diurnal, being all the mechanical effect of prior impulfes. It is with us a conjecture, that the comets were once planets, or moved in orbits as little elliptical. As to the obliquity of thofe orbits, a thousand caufes might be affigned; and we likewife conjecture, that the orbits of the planets not only grow more and more elliptical; but that, when they grow greatly fo, the obliquity of the plane of their orbits may increafe likewife.

Whether they then may vifit other Solar Spheres or not, as Mr. Cole conceives the Comets do, we prefume not to fuppofe or controvert.-As to Mr. C's note on the vis inertia, we hall come to that fubject presently. In the mean time, to apologize for having paffed over, what he calls, the principal matters in his obfervations on light, we beg leave to obfervo that, having, in different parts of our Review, given our ideas of the fubject, we did not think it neceffary to repeat them. On the other hand, if Mr. Cole had not taken us particularly to talk in his pamphlet, we fhould have poffibly paffed it over with ftill lefs notice. It cannot be reasonably expected, that the Reviewers fhould write whole treatises, in juftification of their occafional strictures on thofe of others.It is fufficient, if we are able, when thus called on, to fhew that we do not lightly or inadvertently cenfure what we do not understand. If on fuch occafions, the majority of our readers should accufe us of prolixity, we hope the neceffity of the oc

Add to this, we received an anonymous letter, as heretofore mentioned, not couched in the most gentlemanly teims, on the fubject. Rev. cafion

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cafion will plead our excufe. To go on, therefore, with Mr.

C's letter.

"You say," "if I had read Mr. Melvill's Experiments, I should not have asked the question." What question? I did not ask any question at all. I faid indeed that I could not tell upon what experiments you founded your notions; that notion particularly which I took the liberty to controvert, viz. "That Light is a vibratory motion propagated in right lines, through a feries of clattic bodies conftituting the medium called æther." And I faid this upon the most perfect conviction that no fuch experiments ever exifted. Not one of Mr. Melvill's experiments gives the leaft colour to this doctrine. They proceed all, indeed, upon the direct contrary fuppofition, viz. that Light confifte of bodies, or particles, abfolutely distinct from the medium through which they pats."

We are forry to find Mr. C. fo difingenuous as to mistake here the point in queftion. The petty cavil, about the form of the question, is alfo a contemptible quibble. On a man's declaration of his ignorance, may be justly prefumed his defire of being informed; which is, in fact, though not in words, afking a question.-The matter thus in queition, was not that which Mr. C. above fpecifies. It did not relate to the general nature of light; but to the query "whether light may be made to converge to a focus in a tranfparent flid, without heating fuch fluid." And that it may, Mr. Melvill's experiments prove. We well know that Mr. M. adopted the New-, tonian theory refpecting the matter and motion of light; a theory attended with the greateft difficulties of conception; not, the leaft of which is Mr. Canton's expedient, to remove the abfurdity of light's being at once penetrable and impenetrable, by fuppofing the particles, conftituting its rays, to follow each other at a confiderable diftance. This opinion is, neverthelefs, adopted by Mr. Cole; who might very fafely pronounce that the propagation, of vibratory motions, in right lines,' every way, through the elaftic particles of ather, was never manifefted by experiments; at leaft by fuch kind of experiments as require ocular proof. The rays or particles of light, though the means or medium of fight, are, for that very reafon, invifible. It does not follow, nevertheless, that the pofition is not true, because it is not demonftrable by phyfical experiment.. Many of the ftri&teft mathematical truths ftand in the fame predicament.

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"I muft, repeat once more, that I cannot tell where a fluid is to be found, which is not compoted of gravitating bodies. You, Sir, mott certainly have not yet told us. For within the well-exhausted receiver of an Air-pump, and in the spaces between the atmosphere of the planetary bodies, may be found a fluid in which exift few gravita VOL. VI.

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ting

ting bodies." I should indeed be apt to affume a more pofitive tone, and to fay, that thefe and all other Auids are entirely compofed of gravitating bodies."

The tone of this gentleman is, indeed, fufficiently pofitive. He cannot tell, he fays, and yet he will tell, notwithstanding; because truly, we have not told him. The truth, however, is, that we did tell him plainly enough, had he been willing to comprehend us. The fluid, exiting in a well-exhaufted receiver and between the atmospheres of the planets, is not entirely compofed of gravitating bodies; though fome few fhould be found there. The Reviewer faid few, or no, fuch bodies.Mr. C. unfairly leaves out the words, or no; which plainly fhew that the Keviewer meant, there would be none at all, if' the receiver could be entirely exhaufted, or the atmosphere abfolutely furmounted; both which are perhaps impracticable, Mr. C. indeed may obje&t that within a receiver, entirely exhaulled of the gravitating parts of the atmosphere, there would exift no fluid.-There would exift, however, that medium through which light is propagated: call it a fluid, or what you will, it matters little: it gravitates not, but is merely elaftic.

"I take all poffible fhame to myfelf for having omitted to lay expreffly that water is a non-elastic fluid. And I freely own, that the diftinction should have been made. You will however obferve, Sir, that I introduced this experiment, not to prove, but merely to illuflratt, my pofition; to fhew the manner in which motion is expanded through fluids in general. And I chofe water for this purpose, because it is the only fluid in which fuch undulatory expanfion can be rendered vifibile.”

To make things vifible illuftrative of things invifible, is the neceffary expedient of Theologifts; Moralifts may have recourfe to analogy; Poets to allufion; and 'Potecaries to their quid pro quo.it is dangerons for Philofophers, to ufe any fuc cedaneum in phyfics. Mr. Cole is, therefore, right, in taking fhame to himself, as a philofopher, for not making the illuftra tion of his argument agree with the proof of it. He lays down a pofition concerning the propagation of motion through an elastic fluid, and illuftrates it by an experiment of its propaga tion through a non-elaftic fluid; which is much the fame as if, in order to illuftrate a defcription of fomething white, he had produced a fample of fomething black. As a contrast, indeed, things of oppofite qualities may ferve to illuftrate each other; but no otherwife. The conclufion, of course, should be directly contrary to that which Mr. Cole deduces from the comparifon. But he could no otherwife, he fays, render fuch undulatory expanfion vifible!It is, indeed, difficult to render that visible which does not exist. We may here adopt the lu

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dicrous