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TIE NEWTONIAX THEORY OF THE TIDES.

417

TIDES.

machinery has been for four months past, THE NEWTONIAN THEORY OF THE three cords of wood has been found sufficient to raise steam enough to carry the whole

Sir,-My old acquaintance, Ursa Mamachinery 24 hours.

“ 6th. The quantity of water evaporated jor, tells us that he is “sufficiently read in per hour, as near as I could ascertain, when

mathematical science to discern that in full operation, has been about 60 gallons.

where there are half a dozen different de“7th. The engine was first started about monstrations contradicting each other, the beginning of Sept. 1835, and continued they cannot be all true.” I do not know to work the pump and four mills only, until what meaning Ursa Major attaches to the March, 1836, at which time the whole ma. word demonstration. I always thought chinery was attached, making altogether that a demonstration was meant to prove nearly 10 months.

the truth of a proposition, so as to render " 8th. The cost of repairs has been very trifling, the whole expense of repairs, that

it a matter of certainty ; in that sense to

speak of demonstrations contradicting could properly be said to belong to the en

one another, would be repugnant to gine during the whole time, will not exceed

common sense. ten dollars.

But are you sure, friend " 9th. With careful attention it is not lia

Ursa Major, that your knowledge in ble to get out of order.

mathematical and physical science is “ 10th. The cost compared with a piston such, that when you read two authors on engine of equal power will not, I presume, the same mathematical or physical submuch exceed one-half that of the piston ject, and find them to disagree, you can engine.

determine which of them is right (suppos“ Ilth. If I was in want of another en- ing one of them to be so); or supposing one gine of about 20-horse power, I would cer- of them partly right and partly wrong, tainly prefer the rotary to the piston engine. “ In conclusion, sir, after answering your

could you separate the chaff from the

corn? I am afraid you could not; or if several questions, permit me to state, that in my opinion the rotary is preferable in many

you could, you surely never read with respects to the piston engine. It can be at

attention that passage you have quoted tended by persons of less skill, is less expen

in your last letter in the Mechanics' sive in transportation, and less expensive in

Magazine from the writings of Dr. Wilerection than engines generally of the piston kinson, which you seem to imagine will kind."

set the matter in dispute in a fair point of

view. Newton is to be compared with In all the foregoing testimonials with

Dr. Wilkinson! What next? Sir Henry respect to Avery's engine, there is great Halford, I suppose, with Dr. Eady. But want of that particular evidence, which let us see what sense we can extract from is required in England, to establish the

this selected passage that is to set the superiority of one kind of engine over

matter in dispute in a fair point of view. -another; it is all too vague and general

“ Supposing (says Dr. Wilkinson) the -all calculation upon established rules

mean distance of the moon from the earth and good data has been avoided. We ac

to be sixty times the radius of the earth ; knowledge, that in America (for which,

and if the law of gravitation be assumed, -indeed, it is intended) the evidence given according to Newton, as diminishing as will have, perhaps, more effect than any

the square of the distance increases, it founded upon calculation - engineers will be evident that 60 multiplied by 60 beiug there but little accustomed to look

being equal to 3600, will express this beyond the surface of matters. But here,

proportion, viz. that 3600lbs. on the sur. instances must first be shown to be

face of the earth removed to the moon's founded on general principles, before

surface would only weigh llb. (!)”. So they will be received. Work must be

says the learned Dr. Wilkinson, and so shown to tally with calculation, and cal- believes his enlightened constellate, Ursa culation with work. We would recoin

Major. But in opposition to such mighty mend the American patentees to put up anthority, I(Kinclaven) assert, that Newan engine of their best inanufacture, as a ton never maintained nor ever dreamed sample machine, and submit it to some

of such a thing. Newton has demonsuch trials as Austen's steam-engive un- strated, that if a body is placed at any derwent (see our 643rd Number). When distance above the surface of the earth, we hear the results of such a trial, we

the gravity or weight of this body shall be better able to give an opiuiun. diminishes in the inverse ratio of the VOL. XXV.

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418

OBSERVATIONS ON MR, EXLEY'S squares of the distances; and the only the earth as 11 to 9. Here the Doctor, force, he assumes, that acts upon this forgetting his former statement, now body, is the gravitation of the earth itself. makes the density of the moon (com. But let us suppose that the learned Doc

paring equal bulks) greater than that of ior is righ', and that the body only weighs the earth! He calculates the ratio of 11b. when placed on the surface of the the distances of the centre of gravity from moon, then the force of gravity at the the centres of the bodies to be as 39.788 surface of the moon will evidently be to l; and that the centre of gravity is 1

5880 miles froin the centre of the earth. of that at the earth's surface, for the But the data is far from being correct, 1800

and the answers from that data are body is then acted upon by two opposite wrong; so that the Doctor's knowledge

1

in the simple rules of arithmetic seems 10 forces, the one being and the other 1800

be on a par with bis physical attainments.

Ursa Major says he asked me for an 1

1
1

1
and

explanation of the paradox of the tides,

The 3600 1800 3600 1800

&c. I have already told him that there Doctor assumes the radius of the moon to

is no paradox in the matter, and that

hundreds of explanations and demon2161 be miles = 1080}, hence 240,000

strations have been giveu of il-from the 2

humble explanation of Ferguson to the (the distance between the centres of the

profound researches of La Place. So earth and moon), divided by 1080 =

that it would be an act of supererogation 21?, that is, the distance between the

to give an explanation or demonstration centres of the earth and moon is 212

of that (unless I could do it in a simpler times the radius of the moon; hence

way) which has already been given by so

many. If he is unable to follow their 1 1

1 Х

demonstrations, it is his own fault; he 1800 (212)

= gravitat56899200

might just as well ask me to give him a ing force the moon exerts at the surface

demonstration of the 47th proposition of of the earth. Again, the Doctor assumes

the 1st book of Euclid, because he could the mean depth of the sea to be 4 miles =

not understand that given by Euclid, and 253440 inches; hence (still following

for this reason, too, ihat he could not be

troubled to read the whole of the pro

253440 1 out the Doctor's plan) 86899:200

positions upon which the proof of the 224'

47th depends. We should have lots of that is, the gravitating force of the moon

profound mathematicians, too, if it was

not for that great bore of learning, the

1 will only raise the sea part of an multiplication-table. Indeed, Ursa Ma

224

jor, from your last letter it appears you inch! It is true, the Doctor contrives to ought to take a spell for some time at the make the height of the tide 6 feet; but

“ Tutor's Assistant," and let physical let it be remembered, the Doctor assumes

science alone until you are better prethat the moon exerts one-half the force of pared to enter upon the study of it. gravity at the earth's surface to what she

I am, Sir, yours, &c. does at her own surface!! Whereas I

KINCLAVEN. have supposed (taking Newton for my guide) that the gravitation of the moon follows the same law as that of the earth,

OBSERVATIONS ON MR. EXLEY'S NEW namely, the inverse ratio of the squares

THEORY OF PHYSICS, of the distances. But enough of this Sir,- The following paper, containing part of the Doctor's nonsense.

observations on “Mr. Exley's new Theory The Doctor then proceeds to find the of Physics," was written soon after that centre of gravity between the earth and gentleman's reply to some former stricmoon, assuming the distance between tures of mine on the same subject, but their centres = 60 semi-diameters of the has been delayed in consequence of my earth, the moon's diameter 2161 miles, wish to append to it an examination of their mass in the ratio of 49.22 to 1, and the validiiv of the distinction between the the density of the moon to the density of primary and secondary qualities of mat

(2123

NEW THEORY OF PHYSICS.

419

ter. An arduous profession allows me should aspire to explain all the pheno. little leisure for such pursuits, and the mena of inorganic nature, by deriving subject is difficult. So much time there- them from a supposed original constitu. fure elapsed, that though I continued the tion of the laws and qualities of matter. investigation, having another object in I thought it would be useful to notice the view, yet thinking all interest in Mr. Ex. difficulties which in the present state of ley's theory must have ceased, I long knowledge such an attempt has to ensince gave up the intention of sending counter, and to examine the degree of you even any portion of my paper. Mr. evidence which, in the nature of things, Exley, however, having again brought such a theory is capable of receiving. his i heory before the public, through the am sorry, therefore, that the observations medium of the British Association during in the reply with which Mr. Exley has its late sittings at Bristol, I am induced favoured you should not have led directly to revise my opinion respecting the pro- to such an enlarged and philosophic dis priety of resuming the discussion, for cussion ; that he should not have wil. though this communication is out of date, lingly engaged in throwing as much light in a controversial point of view, yet the as possible on these 'most interesting and general subject is of no fugitive charac- important topics, with an especial referter; and the theory itself is likely to have ence, though it may be, to the corrobora. a permanent interest attached to it, by tion of his own theory; that he should the very favourable manner in which it have thought it more advisable, or at was received by Doctors Dalton and least quite sufficient, in defence of that Thomson. I shall not, however, enter on theory, to indulge merely in a running the abstruse inquiry alluded to above, comment on what appeared to him obbut merely subjoin my view of some jectionable points in my communication; metaphysical consequences which must and that the general tone of his remarks result from Mr. Exley's physical doctrines. should imply, that I had not touched

It is announced that Mr. Exley has upon the more useful investigation albrought forward in favour of his hypo- luded to, and had not applied the conthesis some fresh facts in relation to the siderations which arose in the inquiry, as specific gravity of the gases. If these well for as against his theory, but that I instances of verification do not rest on had merely strung together a series of ad. principles, data, and results, which run verse observations or captious objections. in a circle, and acquire inerely a mutual, The most interesting point, as also the self-derived support-if they are upheld pivot on which the controversy turus, is by collateral and independent proofs, and the inquiry concerning the probability of by a course of reasoning untainted by Mr. Exley's theory being the true system subsidiary hypothesis - I shall receive of nature. If, without any doubi, the great satisfaction from the circumstance, principles on which it is founded were for my prepossessions are entirely in what he asserts they are-certain ulii. favour of Mr. Exley's theory; and I shall mate facts or truths-still there would be eager to congratulate him on his hav. be room for a reasonable degree of sceping verified it, though but in part, after ticism, grounded on the possibility of that more satisfactory and unexception- some unknown principles affording, conable manner, the necessity of which is jointly with the others, a more satisfacpointed out in the following paper. tory explanation of phenomena. But I am, Sir, yours truly,

those principles, wanting the character of BENJAMIN CHEVERTON. axioms, and heing avowedly advanced as

postulates, he is not in a position to chalSir,- In the review which I took of lenge so confidently the attention of sci“ Mr. Exley's new theory of physics," I entific men to his theory as he otherwise was sincerely desirous of forming an im- would be entitled to do; and I fear that partial estimate of its merits; and I can- even as an hypothesis-plausible, ingenot think I failed, because I felt called nious, and elaborate as it inust be alupon to moderate in some degree the ex- lowed to be it has not met with that pectations of its author. I wished, also, reception which, from its extensive applito embrace the opportunity of making cability, and the numerous accordances some general observations on that, or any therewith of observations and experiother theory of physics, which, like it, ments, it justly deserves. For it must be 420

OBSERVATIONS ON MR. EXLEY'S

sense."

in allusion to this theory, that Sir John the extended heavens, and downward to Herschel observes, in his “ Discourse on the unextended centres of atoms." Here, the Study of Natural Philosophy:"- again, it is taken for granted, that be“ Molecular attraction has been attempted cause gravity attaches to the ultimate to be confounded by some with the gene- particles of matter, that it must extend to ral attraction of gravity, which all matter ihe centres of the atoms, pervading or exerts on all other matter; but this idea constituting their very nature. Besides, is refuted by the plainest facts."*

independently of the law, the quantities In order to strengthen his position, that of the forces in action between atoms and the first principles of his theory are unde- between masses may be different, for niable physical truths, Mr. Exley observes, aught that any thing in the present state that " these principles are not arbitra:ily of knowledge can be brought to prove assumed, but are themselves analytical the contrary; and although this is not deductions; and although named post- enough to affect the validity or the suffilates, they are such only in a certain ciency of the fundamental principles of

It is also, I presume, only in a Mr. Exley's theory, it is sufficient to show certain sense he would have us under- that their existence cannot with any cer. stand that they are “ analytical de tainty be deduced from the universal ductions.". Undoubtedly, it was from a existence of gravity. They may be inreview of the various phenomena of mat ferred from various analogical and phiter, that he was led in a general manner, losophical considerations; and that is the analytically and inductively, and not ar- ground on which he should be content, bitrarily, to fix on these principles as for the present, to rest them, corroborated being of themselves sufficient on which as they are by the evidence derived from to erect his system ; but will he affirm, the numerous accordances already rethat he has entered on so pointed and

ferred to.

It is quite in vain that he definite an analytical investigation of any takes the high ground of insisting, that phenomena, as should make an inference they are ultimate natural truths and of these principles therefrom, a necessary facts, and it must be in vain, until the indubitable consequence. If so, let him laws of atomic action have been more publish it, by all means, and it shall bave fully investigated by experimental remore weight towards the establishment search. He has made an effort to antiof these principles, than any proof derived cipate the natural progress of knowledge, from the agreement of experiments or and he must be satisfied accordingly with observations with deductions froin them. the position he has taken, and with havCan he, for instance, bring forward any ing his system regarded as a not improanalysis which shall unequivocally indi., bable hypothesis, to be kept in view in the cate that the law of attraction between future progress of science, for the purthe atoms, to say nothing of the law of pose of having its principles established repulsion, is in the inverse ratio of the or refuted; and he should perceive, that square of the distance. He will refer us, in the mean time he is not entitled to probably, to the heavenly bodies, assert- claim attention to it as an undoubted ing that “the voice of all their actions and unquestionable theory. If it were makes it appear that gravitation belongs such if this distinction were conferred to every atom of matter.” This may be, on it, as he contends it is, by my definibut it is begging the question, if he would tion of a theory, namely, that it is “ a thence infer, that the law of molecular system whose first principles are ultimate attraction is proved by the law of grari. natural facts or truths, whether self-evi. tation, for he must first assume that these dent or analytically traced through a forces are the same. He further ob- course of observations or experiments”. serves, “ Analysis carries us upward to how is it that Mr. Exley's principles, if

facts or truths, can admit of any doubt * This hypothesis, however, cannot be so very absurd, or Sir John Herschel would not have be.

in any one's mind ? How is it that only stowed any notice on it; he surely, therefore, might

their fitness to explain phenomena is plainly refute it. The truth is, that the assumption

brought forward to justify our belief of of knowledge on subjects of this kind, in so very

their existence ? confident a tone, whether it be in the way of Then as to the law of repulsion-have affirmation or denial, is equally to be deprecated, as unphilosophical, and as unfavourable to the

we even as good a warrant for it as for progress of discovery.

the law of attraction ? Do the experi

have referred us to a few of those facts which so

he says,

NEW THEORY OF PHYSICS.is

421 ments on compressibility countenance it? possibly be implicated therein, than those but this discrepancy, it may be said, which we have adopted, or that our racan be explained away on the hypothesis, tionale of nature's procedure is her true however be it remembered, of the escape modus operandi ? We want, as I said in of ethereal matter. In order to avoid in my fornier article, the “ Instantiæ crucis," some measure the too inanifest appear. of which Bacon speaks, to decide the ance of the gratuitous character th question by rejecting all the causes but law, Mr. Exley would lead us to conceive one;" and I must again repeat, that of repulsion as being an inverted kind of “ Mr. Exley has precluded himself from attraction, and that therefore the law that inore satisfactory analytical proof, must needs be the same; “Gravitation," by an exclusive adoption of the strict

" extends to the centre of atoms, synthetical form.” To which he replies, while near the centre its direction is re- « this is said unadvisedly; a little thought versed.” Besides unnecessarily compli

would show that these principles are not cating the hypothesis, in expression at adopted arbitrarily, bui are themselves least, how can we imagine that antagonist analytical deductions they are the deforces, although the law may be the same, mands of nature herself-the very results can be identical.

of that more satisfactory analytical proof." It would be wrong to limit the progress No, no, I have not spuken unadvisedly, of science, but it is not unreasonable to but with a perfect knowledge both of doubt whether discovery will ever reach what I meant and of what I said. The to the primary laws of atomic action, in truth is, Mr. Exley has not given suffiany very direct and satisfactory inanner. cient consideration to the tenor of my Supposing Mr. Exley's conjecture to be observations, nor weighed sufficiently, the true, that molecular and universal attrac- import of my words, I did not then. tion is the same force, what an almost allude tu nor speak of his principles as infinite distance apart on the scale of in- wanting the character of analytical de. tensity must our inquiries be conducted, ductions, though, as I have now shown, and how are we to connect thein together, they, strictly speaking, are really not enso as to acquire proof of the identity of titled to it; but I said that the system the qualities investigated? What can viewed as a whole--and not then queswe apply as a common measure to such rioning the principles on which it is wide extremes? A mountain is required

founded was in want of that more sa. to produce the slightest deflection of the tisfactory proof which Bacon had deplummet, and yet what an immensity of scribed, and which I quoted ; or, at least, force do the phenomena of cohesion ex- that Mr. Exley had not advanced such hibit ? Doubiless the atoms of matter, proof in support of it. Admitting his , as every thing teaches us, are almost in- first principles to be truemadmitting they finitely small; and this consideration pre- are what they are not--a legitimate anasents us with a solution of the difficulty lytical induciion from phenomena-still, as a matter of fact, but at the same tiine in reference to the system founded on it immeasurably adds to the difficulty as them, proof is required that they alone a matter of investigation and proof. are quite sufficient, and that they only are

But let us admit that the first princi- adequate to explain the processes of ples of Mr. Exley's system are unques- nature; and this proof is afforded, when, tivnable-let it pass for a moment as a on an examination of all possible modes genuine theory, we shall next have to as- of accounting for things, the whole of certain whether it be a true theory, that thew are rejected save one. This is the is, whether there be a sufficiency in the analytical proof (that was my word) of principles, and a right mechanism in the the validity of a system, and by implica- : process, from which and by which we tion of the fitness and adequacy of its are to work out all the results of nature. principles. Now this proof is of course We are to ascertain whether this world brought forward subsequently to the sysof our concocting belongs to reality or !! tem being framed, but Mr. Exley has pure imagination. Every thing may be confounded it with the prior analytical made out very plausibly, but are we cer- induction of the fundamental principles, tain that the phenomena can be explained which equally, of course, must be ad. in no other and no better manner?

Are vanced before the system can be frained; we assured that no other principles can and because he has not distinguished be- :)

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