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mark of novelty, in the whole book. Of the style we shall say but little; it deserves no violent censure, and certainly no violent praise. What kind of logie is this?

If we persevere without wavering in our purpose, we must ultimately be successful; and though success is not always the test of merit, yet, if reason is the test of truth, it cannot be doubted, even though we should not, that we ought to succeed.' P. 223.

Neither is Mr. Burdon very correct in his language, in page 276:

But if we must find a parallel for him in the history of antiquity, let us rather liken him to the cruel and crafty Philip, than to his generous and magnanimous son, though he has the worst parts of both, without being exactly like either.'

He talks of the lust of concupiscence.' We suspected the words 'lust' and 'concupiscence' to be synonimous; and found our suspicions confirmed by Dr. Johnson.

Mr. Burdon is a great sceptic; he entertainsgreat doubts 'whether the sum total of the advantage which has resulted from the French expedition to Egypt, either to the natives of that country or the rest of the world, can balance the fatal precedent of so gross an attack upon the laws of society. But after much deliberation pro and con, he apprehends, in the next page, that 'upon the whole, the evils which the army, and the natives of Egypt endured, from the first departure of the expedition, till the French finally evacuated the country, infinitely overbalance any trifling advantages which may be derived to any of the parties concerned.'

The reflections on sir Sidney Smith are weak, illiberal, and unjust; those on Djezzar Pacha (or, as Mr. Burdon affectedly calls him, 'the Djezzar') are equally so, and shewthat the writer is but inadequately acquainted with Turkish customs. They are also inconsistent with the partial encomiums which he himself ocсаsionally, and perhaps deservedly, bestows on the tyrant whose life he records.

No opportunity is omitted of making us acquainted with the author's attachment to liberty, his aversion from the cause of kings, and his anxious desire for reform and melioration in all monarchical governments. We read in, page 17, that the Austrians were superior to the French in every thing but the justice of their cause, and the genius of their commander.' Soon afterwards we are told that 'the splendid campaign of 1797 taught the coalesced powers that French valour and a good cause were advantages against which the cause of princes could oppose but a feeble resistance. Had the conduct of the French been equal to their professions, and worthy of the cause in-which they were engaged, &c. Pages 72 and 207 display the

same spirit. Another part contains a detailed account of the dis
asters which have befallen Germany; all which, says Mr. Burdon
' were the blessed results of Bonaparte's conquests in Italy, or,
properly speaking, of the first coalition against French liberty.'
We too can glow at the name of liberty: but we cannot couple
that sacred name with the name of Frenchmen; we can bestow
no praise on the cause which attracts so much of Mr. Burdon's
admiration;--that cause whose notorious and avowed object was
the subversion of established governments, and the dethroning
of legitimate kings. We apprehend, and the justice of our ap-
prehensions is proved by the experience of ages, that liberty or
universal equality is but a name; an ideal blessing which
exists only in the declamation of school-boys, in the imagination
of poets, in the dreams of a visionary philosopher. Its theory
is delightful; but the depravity of human nature, or some
other cause, has ever prevented its being carried into practice.
It is a phantom in the pursuit of which the blood of thousands
has been spilt; which misguided enthusiasm is delighted to
chase, but-

Hæret hians, jam jamque tenet, similisque tenenti
Increpuit malis, morsuque elusus inani est.'

:

Before Mr. Burdon is dismissed, it must be allowed that there are several parts of his work which, to those who do not happen to have read them before, will doubtless afford amusement: such are, in particular, the ceremony of the presentation of Bonaparte to the directory, page 85; the description of the passage of the Alps, page 155; &c. &c. We shall conclude by wishing, not for the sake of his glory, but of our own instruction, that Bonaparte may meet with a more able historian.

ART. V.-Elements of Mechanical Philosophy, being the Substance of a Course of Lectures on that Science. By John Robison, LL.D. Professor of Natural Philosophy in the University of Edinburgh, Fellow of the Royal Society of Edinburgh, of the Imperial Academy of Sciences at St. Petersburgh, and of the Philosophical Societies of Manchester and New York, &c. Vol. I. including Dynamics and Astronomy. 8vo. 11. Is. Boards. Cadell. 1804.

ALTHOUGH the business of critics is with books, and not with their authors, yet, as it was likely to happen, the character of Dr. Robison excited within us a curiosity to see what was said by him on a subject, by general acknowledg ment, arduous and intricate. The plan, the conduct, the use

1

fulness, and the merits, of his work, may be understood from the subjoined analysis and our occasional comments: these are given nearly as they were suggested by progressive perusal.

The title page announces the contents of the present volume to be Dynamics and Astronomy, but the former subject is treated with considerable restriction: no application is made of the doctrine of powers and moving forces, to the motion of 'bodies along inclined planes, to the motion of bodies connected by levers, &c.; and consequently the present volume contains nothing concerning the centres of oscillation, gyration, &c. It should seem the main object of the author is, to illustrate and to familiarize the philosophy of Newton; and to show, in the motions and perturbations of the planets, in the figure of the earth, and in the phenomenon of the tides, the universality of the law of gravitation.

- In the order and mode of demonstration Dr. Robison treads very nearly in the steps of our great philosopher; as continued 'quantity, as curves and variable motion, were to be the subjects of discussion in the 'Principia, Newton prefixed his first section, by which he taught how continued quantity was to be measured and estimated. He stated his axioms and rules geometrically. The author of the present work begins it with certain propositions concerning prime and ultimate ratios or limits, and proves them by the aid or intervention of diagrams. This doctrine of prime and ultimate ratios, or of limits, by its nature, if we may so express ourselves, is not without great difficulties. It is very perplexing and embarrassing to beginners: the doctrine has not been clearly and accurately propounded. Newton is not able to satisfy the doubts and objecting inquiries of the true searcher after truth; and the obscurity of his doctrine is not dissipated by the light that Dr. Robison has thrown upon it: if he was clear, he would be very brief; but, in our opinion, he has done nothing to remove the ancient prejudices concerning the connection or concomitancy of brevity and obscurity. Preliminary propositions concerning limiting ratios, or concerning that method in fact by which continued quantity is to be estimated, very properly precede any discussion relative to force and velocity. These are mere terms, the creatures of definition; and from the definitions to know their value and mathematical measure, recourse must be had to fluxions, or to the differential calculus, or to the method of limits: thus the symbol for the velocity is , the symbol for the force istor and particular instances being given, to know how to exe press in algebraic terms the value of such symbols, we must apply the rules of the mentioned calculi. Dr. Robisón begins, and properly enough, with uniform motions; and deduces the

t

D

free from

common and known formulas that subsist between the spaces, velocities, and times. He then passes on, to the consideration of variable motion; and here, in our opinion, the learned professor uses more words than are necessary: indeed, in certain, passages, he seems not entirely free from the thraldom and mystical influence of words; - he talks about a body having a. potential velocity, and a certain determination; and this is the more remarkable, since extracts will be exhibited by us not only of clear and accurate argumentation, but in which the author insists on the necessity of using words of a precise signification.

The professor's proposition concerning the method of estimating the velocity, we do not much approve of: from this proposition it is deduced, as a corollary, that the velocities are in the ultimate ratio of the spaces described in equal moments of time. The author then adds: 'It often happens, that we cannot ascertain this ultimate ratio, although we can measure the spaces described in very small moments. We are then obliged to take these as measures of the velocity.' This passage either we do not rightly understand, or, if we do understand it, it is manifestly wrong: if, in the language of the modern mathematicians, the space be a function of the time, or if * =st, what is the case in which we cannot compute?

After the composition of motions, which is well explained and illustrated, Dr. Robison proceeds to show, after Newton, that the areas are proportioned to the times; that the velocity varies inversely as the perpendicular; &c.: he also deduces the several expressions for the force, a body moving in a right line towards the centre of force, or describing a curve line round the centre of force; that is, he proves expressions such as these,

x

f ===

t

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(arc)

=

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and

F= chord of curve. chord of curve. he distinguishes properly, as Dalembert has done before him, between the measure of the force, the body moving in a polygon, and the measure, the body moving in a curve.

In the second section the author defines dynamics to be 'that department of physico-mathematical science, which contains the abstract doctrine of moving forces; that is, the necessary results of the relations of our thoughts concerning motion and the causes of its production and changes.' This passage is rather obscure and vague: what does the author mean by 'the causes of its production'? The next passage will inform us changes of motion are the only indication of the agency, the only marks of the kind, and the only measures of the intensity of those causes.' We know nothing then of causes: we can indeed talk about them, by making terms stand for effects; and dynamics

in fact, treat only of effects, of spaces described, and of the mathematical laws of their description -But, considering the great and general merit of the performance before us, we seem to ourselves degenerating into petty and peevish criticism; we turn, therefore, with satisfaction, to certain passages in which the author's perspicuity, accuracy, and mental vigour, eminently shine forth.

These mechanical affections of matter have been very generally called powers or forces; and the body conceived to possess them is said to act on the related body. This is figurative or metaphorical language. Power, and force, and action, cannot be predicated in their original strict sense, of any thing but the exertions of animated beings; nay, it is perhaps only the exerted influence of the mind on the body which we ought to call action. But language began among simple men; they gave these denominations to their own exertions with the utmost propriety. To move a body, they found themselves obliged to exert their strength, or force, or power, and to act. When speculative men afterwards attended to the changes of motion observed in the meetings or vicinity of bodies, and remarked that the phenomena very much resembled the results of exerting their own strength or force; and when they would express this occurrence of nature, it was easier to make use of an old term, than to make a new one for things which so much resembled; because there are always such differences in other circumstances of the case, that there is little danger of confounding them. We are not to imagine that they thought that inanimate bodies exerted strength, as they themselves did. This was reserved for much later times of refinement. In the progress of this refinement, the word power or force was employed to express any efficiency whatever; and we now say, the power of aqua fortis to dissolve silver. -the force of argument the action of motives, &c. &c.

To this notion of conveniency we must ascribe, not only the employment of the words power and force, to express efficiency in general, but also of the terms attraction, repulsion, impulsion, pressure, &c. all of which are metaphorical, unless when applied to the actions of animals. But they are used as terms of distinction, on account of the resemblance between the phenomena and those which we observe when we pull a thing toward us, push it from us, kick it away, or forcibly compress it.

• Much confusion has arisen from the unguarded use of this figurative language. Very slight analogies have made some animate all matter with a sort of mind, a ώσπερ ψυχη, while other resemblances have made other speculatists materialize intellect itself.

The very names which we give to those powers which we fancy to be inherent in bodies, shew that we know nothing about them. These names either, like magnetism, express a relation to the par ticular substances which we imagine possess the power, or they express something of the effect which suggested their existence. Of this last kind are cohesion, gravity, &c. They are almost all verbal derivatives, and should be considered by us merely as abbre, viated descriptions or hints of the phenomena, or as abbreviated

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