Εικόνες σελίδας
Ηλεκτρ. έκδοση
[ocr errors]
[ocr errors]

nating in a solid rather than in a liquid, that when water becomes solid, this force gives way to the repulsive, and the ice expands. Nor are the attractive and repulsive forces in any equilibrium' in elastic fluids; the repulsive force exists here alone, and only compensated by external pressure or gravitation. It is in liquids and in solids that the attractive and repulsive forces exist in different states of equilibrium,' and probably without differing materially in degree; for the compressibility of ice appears to differ very little from that of water, and the immediate force of cohesion is intimately connected with the compressibility: but the true distinction between solids and liquids is the hardness or lateral adhesion of the one, and the perfect freedom of lateral motion possessed by the particles of the other; and if it were necessary to assign a cause for this distinction, there is none that we could point out with greater probability, than a certain symmetry of arrangement, or an approach to crystallization, in the particles of solids, while those of fluids might be supposed to be collected together without any uniform order, and so far to be perfectly independent of each other.

P. 84. It appears from the researches of Professor Robison, that in a vacuum all liquids boil about 145° lower than in the open air. Such an observation as this could scarcely have been made with any propriety, even before the speculations of Mr. Dalton had assisted us in forming more correct ideas on this subject. A liquid placed in a perfect vacuum might be said to boil at any temperature, however low: since the temperature at which any liquid boils is wholly dependent on the pressure to which it is subjected. We may however easily understand Professor Robison's experiments, by interpreting the term vacuum as relating to the receiver of an ordinary air-pump, not in the best repair, in which the mercurial gage would stand at about two-thirds of an inch; for in such an atmosphere as this, both water and alcohol would in reality have their usual boiling points lowered about 145°.

[ocr errors]

P. 92. The inaccuracy' of the thermometer must be rather increased than counteracted,' by the disparity of the expansions of fluids and solids, if it is really such as our author states it.

P. 94. With repect to heat, Sir H. Davy still professes himself an advocate of the opinion of Bacon and Newton, that it depends on a vibratory motion of the particles of bodies: but, however powerful we may allow some of his arguments to be, we cannot agree with him in thinking, that the acknowledged existence of a motion' of expansion or contraction will go very far to prove the intimate nature of the cause of that expansion or contraction.

P. 136. The capability of thin plates, to receive a much stronger charge of electricity than thick, is here attributed to the difficulty

with which non-conductors receive polarity.' Surely the explanations of Cavendish and Robison are much more luminous.

P. 141. The resemblance of the Aurora borealis to the discharge of electricity through rare air was very naturally adduced by Franklin in illustration of that phenomenon; but it cannot be admitted as a sufficient explanation, until it be shown in what manner the magnetical effects of the Aurora borealis are produced, or why its beams are always parallel to the dipping needle.

P. 149. The different powers of Voltaic batteries consisting of large and small plates, although perhaps somewhat too strongly contrasted, are very happily exemplified by experiments conducted in pursuit of Mr. Cavendish's idea of the different effect of a great quantity of electric fluid, and a great intensity of charge; and very interesting accounts are given of the operation of Mr. Children's large plates, and of the gigantic apparatus of 2000 double plates, procured by subscription for the use of the Royal Institution: but we must be contented with merely pointing out these experiments, without attempting to give a particular abstract of them.

P. 168. Sir H. Davy confirms Mr. Ehrman's discovery of unipolar bodies, which discharge the electricity of either end of the Voltaic circuit taken separately, but when connected with both, retain the character of one only; soap, for instance, remains positive, and the flame of a common taper negative.

P. 219. Note. The optical experiments here mentioned cannot certainly be sufficiently explained on the idea of attractive poles on opposite sides of the particles of light.' These experiments prove, if they prove any thing, not only that homogeneous light, at certain equal distances in the direction of its motion, is possessed of opposite qualities, capable of neutralising each other'; but also that these qualities affect the collateral rays of any single beam in a manner precisely similar at equal distances from the radiant point: so that it would be necessary to suppose a continued stratum or film of particles to be thrown off by every luminous point, many millions of millions of times in a second, and to proceed in all directions, like an expanding shell, with an inconceivable velocity, to immeasurable distances. We do not state this as an impossibility, but as a condition necessary to be taken into consideration, without which our author's conjecture would be wholly inapplicable to the pheno


P. 233. It is very justly observed that atmospheric air has not been found to differ perceptibly in its composition in the most dissimilar situations, containing always 21 of oxygen, and 79 of azote or nitrogen; that is, as it should have been added, by measure.

P. 296. A peculiar hydrophosphoric gas is described, which was discovered by the author in February, 1812; but which appears to

F 2




[ocr errors]

have been previously known to Böckinan and others. P. 320. Some very accurate and decisive experiments are mentioned, which seem to determine finally that the carbureted' or carboneted hydrogens contain no oxygen, and that they exist exclusively in the forms of carbureted hydrogen,' and 'supercarbureted hydrogen,' or olefient gas. P. 382. Stannane' seems to have been known

to Proust.

[ocr errors]

P. 391. It is observed that the colours on a polished surface of heated iron cannot depend on oxydation, as they take place under mercury.' But they appear between the temperatures of 430° and 580°, when the mercury has not yet boiled, and when we cannot be certain that all air has been excluded. In the case of lead, there is positive evidence that these colours are derived from the formation of litharge; and in that of iron, it appears almost impossible to doubt that they are the beginning of the scales of oxyd, which are actually thrown off, when the heat becomes more intense.

P. 435. Palladium is said not to have been found in sufficient quantities to be applied to the purposes of the arts.' But, if we are not misinformed, its ingenious discoverer, who seems to set all quantity at defiance, has furnished an auropalladium, or an alloy of this metal with gold, for the graduations of the magnificent circular instrument, which has lately been constructed by Mr. Troughton for the royal observatory at Greenwich; this alloy having the appearance and durability of platina, and being of a hardness better adapted for receiving the divisions.

P. 492. The powder of Algarotti' seems to be a submuriate, and not an oxyd' of antimony.

[ocr errors]

P. 498. The solution of potassium in hydrogen is made the basis of the explanation of the ready production of potassium by means of ignited iron filings: but we had before been told that sodium may be obtained in the same manner, and that sodium is not soluble in hydrogen; pp. 331, 335. The attraction of potass to the oxyd of iron is alleged by others, with more consistency, as a predisposing or potential affinity.

The character of Sir Humphry Davy's researches has always been that of the most interesting originality, and we have certainly no reason to complain that he has in his experiments very commonly forsaken the beaten path. But in a general work like the present, it was impossible that every thing which was required should be supplied from what he had himself discovered or confirmed, and in reporting the labours of others, he has sometimes allowed inaccuracies to escape him, which a little more plodding diligence might have avoided. The processes for obtaining the metals in purity are often of this description: they might perhaps very properly have been omitted or deferred, as not sufficiently elementary to


be read with advantage by a student: but if they were to be inserted, it would have been better to have rendered them a little more intelligible; and the entering into such an explanation of each process might often have led the author to have considered all its steps with more attention, and to have inquired if they afforded the best possible means of attaining the desired end. He seems also in many instances to have trusted too much to his memory in asserting the nonexistence of certain combinations, especially those of several of the metals with carbon, and of some with sulfur. In a future edition, it will be necessary to correct several numerical and verbal errors, besides those which are pointed out in the page of errata. P. 271, line 6 from the bottom, for 1.9 read .19. P. 332, l. 15, for stannane read tin. P. 371, 1.9 from the bottom, for two, probably, three. P. 413, 1. 6 from the bottom, for 2 to 3 read 3 to 2. P. 445, §8 is a repetition of §5. P. 449, 1. 20, is either a misprint or a mistake. P. 468, l. 19, for soda read potassa. P. 497, I. 7 from the bottom, for very, read not very. P. 501, last line, for square inch we must probably read inch square. App. page 2, 1. 3, for

11.026 read 4.026.

The present volume extends only to the general laws of chemical changes, and the primary combinations of the undecompounded bodies: how many more such volumes will complete the whole of the projected Elements, it has probably not yet been possible to determine. With all its excellencies, this work must be allowed to bear no inconsiderable marks of haste, and we could easily have conjectured, even if the author had not expressly told us so in his dedication, that the period employed on it has been the happiest of his life.' In that, and in every other happiness which may have befallen him, we shall ever most sincerely rejoice, nor shall we think the public will have any reason to reproach him with having done too little for science, even if he should fail, at any future time, in his avowed resolution of pursuing it with unabated ardour;' that he has not yet so failed, is become, from a late accident, a matter of public notoriety; and if we may expect perseverance to be at all commensurate to success, we have no reason to be apprehensive of his passing any part of his life in inactivity.

The style and manner of this work are nearly the same with those of the author's lectures delivered in the theatre of the Royal Institution; they have been much admired by some of the most competent judges of good language and good taste; and it has been remarked that Davy was born a poet, and has only become a chemist by accident. Certainly the situation, in which he was placed, induced him to cultivate an ornamented and popular style of expression and embellishment; and what was encouraged by temporary motives has become natural to him from habit. Hence have F 3 arisen

arisen a multitude of sentimental reflections, and appeals to the feelings, which many will think beauties, and some only prettinesses; nor is it necessary for us to decide in which of the two classes of readers we wish ourselves to be arranged, conceiving that in matters so indifferent to the immediate object of a work, a great latitude may be allowed to the diversity of taste and opinion.

ART. V. Count Julian: a Tragedy. London, Murray. 8vo. Pp. 128.

THE author of the drama before us, has taken a very different view of Count Julian's character from that in which the Spanish writers represent him. He is not

El injuriado Conde, a la venganza

Atento, y no a la fama.

as Luis de Leon describes him, a man sacrificing his country and his faith to the gratification of his revenge: the Julian of the tragedy is a hero and a patriot, seeking as much to redress the wrongs of his country as his own peculiar grievances; but unhappily attempting to effect it by the assistance of a foreign power. Repugnant as this representation of Julian is to the feelings of a Spaniard, and to those which are drawn from Spanish history, it is less so than the liberty which has been taken of ennobling Opas, the archbishop of Seville, a renegado and a traitor, whose name is detested in the peninsula. The author does not seem to be sensible that this can produce an unpleasant effect. It is remarkable,' he says, that the most important era in Spanish history should be the most obscure. This is propitious to the poet, and, above all, to the tragedian. Few characters of such an era can be glaringly misrepresented, few facts offensively perverted.' The purposes of the dramatist have certainly been served by this departure from historical verity and received tradition.

The play opens with a scene in the camp of Julian, between that commander and Opas, who is urging him, but vainly, to see his daughter. Julian, who begins to feel the consequence of the victories which he has gained over Roderigo, says of himself,

All my peace

Has vanish'd: my fair fame in after-times
Will wear an alien and uncomely form,
Seen o'er the cities I have laid in dust,
Countrymen slaughtered, friends abjured!
Opas. And faith?

Jul. Alone now left me, filling up in part
The narrow and waste intervals of grief.'


« ΠροηγούμενηΣυνέχεια »