of wrought iron 14 inch in diameter and 12 inches long, being heated to the temperature of 210° in boiling water, was immersed in the oil to such a depth, that the middle of the flat surface of the end of the hot iron, which was directly above the point of the conical projection of ice, was distant from it only of an inch. Agreeably to the expectation of the author, no heat was found to descend through the thin stratum of oil which remained interposed between the hot surface of the iron and the pointed projection of ice; for it did not appear that there was any diminution of the height of this projection, nor any alteration of its form; nor that the ice was in any way affected by the vicinity of the hot iron. A similar experiment, substituting mercury for oil, was then made, and was attended with a similar result. There are other experiments, to shew that radiant heat also does not descend through water, oil, melted tallow, nor melted wax. The principle of all these last-mentioned experiments consists simply in suspending a red-hot bullet above the surface of the substances with which the experiment is made. When ice was used, the quantity thawed was very little, and occupied a small circular excavation of a very inconsiderable depth, but rather deeper at and near to its centre, than at its sides. When tallow or bee's wax was used, the result in one respect was very singularly different; for the surface of the unmelted tallow and wax, instead of being concave, as in the ice, rose up in the form of a protuberance, or very blunt point; the extremity of which reached almost to the surface of that which was melted. From these and the various other trials which the Count has made in the investigation of this difficult and interesting subject, he thinks that he has ground for concluding that all fluids are nonconductors of heat: that is, that heat, in diffusing itself through the mass of a fluid, is not transmitted from particle to particle, de proche en proche, but that the heated particles, becoming specifically lighter by the addition of the heat, rise in the fluid; that, this operation taking place with respect to all the component particles, as they successively come into contact with the heat, the whole fluid mass thus becomes gradually heated; and that, when any substance takes the form of a fluid, all interchange and communication of heat among its particles, or from one to the other, becomes from that moment absolutely impossible. It would be presumption in us to pronounce decisively on the truth and propriety of this conclusion: yet we cannot but think that, in the latter part of it, the author has carried it to an extent which neither his own experiments nor general reasoning on the subject will completely justify; for the power REV. OCT. 1798. N of of communicating and interchanging heat between the particles of a fluid and other substances, and between the different particles of fluids of different specific gravitics, is a fact which, we apprehend, the author himself will not controvert; since the rising and falling of the mercury in the thermometer prove the one, and the freezing of water on ice-cold mercury proves the other. If this be true, why then should it be supposed that, in reference to the particles of the same fluid, this power should be lost? The existence of this power does not at all militate against the mode of the propagation of heat maintained by our author; for, supposing it to exist, still his theory cannot be negatived without supposing the suspension of one of the most powerful and pervasive of nature's laws, that of gravitation :-for, if heat diminishes the specific gravity of any body to which it is communicated, and if a less specifically heavy body will rise in another specifically heavier if in a fluid state, would it not be a most flagrant absurdity to suppose that the integrant particles of water, oil, &c. rendered lighter by the addition of heat, will not rise above those particles of the same fluid which are heavier because colder?-but that the operation of gravity should counteract, by anticipating, this power of communication and interchange between the particles might naturally be expected: for it is reasonable to suppose that some continuance of contact, though it would be difficult to say what, between the integrant particles of a fluid, must take place before a heated particle would give off its acquired heat to another; and on the supposition that the velocity acquired by the heated particle, in consequence of the diminution of its specific gravity, should even be so small as that of 175 part of an inch in one second, and on the supposition that the diameter of an integrant particle is one millionth of an inch,the contact of the particle in motion with any other individual particle not in motion, against which it strikes in its progress, cannot last longer than the 17 part of a second nearly. Though we shall not presume to say that this continuance of contact is not sufficient for the communication of heat from particle to particle, still we think that so very short a duration of contact is sufficient to justify us in our opinion, that the power of communication and interchange is probably only prevented by the operation of the law of gravity; in opposition to Count Rumford's idea that this power does not exist. A considerable portion of this pamphlet is occupied with ob servations on chemical atlinity; the existence of which the ingenious author attempts to argue away, on the idea that the mode in which heat is propagated in fluids is sufficient to explain all the phænomena of chemical solution. In support of his opinion, he adduces one experiment, in which brine and fresh water were made to repose on each other for some days, without manifesting any tendency to mix together: but, on a subsequent application of a little heat, an intimate mixture took place in a few hours. That heat aids solution, and aids it in the manner for which Count R. contends, we have no doubt: but we are disposed to think that enthusiasm for his newly-discovered theory has led him, without sufficient reason, to exalt this powerful auxiliary into an independent principal; for we are at a loss to conceive how, without admitting the existence of an attraction between the particles of matter, the theory itself of our author can be supported; since, how can heat be communicated to a particle of the fluid, unless we suppose some species of attraction between the two? The decision of this difficult question, however, must be left to future investigation. In the course of the work, the Count extends the application of his theory by conjectures concerning the vital principle in living animals, the nature of physical stimulation, and the proximate causes of winds. With much ingenuity and plausibility, he infers, from the non-conducting power of fluids, the probable existence of intense heat in the midst of cold liquids. ART. VIII. The Works of Horatio Walpole Earl of Orford. THE We-find the dedication and preface, written in 1762, exactly the same in the smail edition of 1782, and in that before us. The text seems to have received little alteration or addition since the year 1782. The plates are the same, retouched, as those of the 4th edition of 1762. In the list of Holbein's works, indeed, we expected some addition to have been made, in speaking of "an invaluable treasure of the works of that great master, preserved in the Palace at Kensington, consisting of a noble collection of Holbein's original drawings for the portraits of some of the chief personages of the court of Henry VIII.+"-"It is great pity (says the author) they have * See our literary records, 1762, &c. vols. xxvi. xxx. xxxvii. and lxiv. + P. 71. not been engraved, not only that such frail performances of so great a genius might be preserved, but that the resemblances of so many illustrious persons, no where else existing, might be saved from destruction *." We were the more surprised at the continuance of his Lordship's lamentation on this subject, as the task was undertaken under his patronage, and greatly advanced in a most exquisite manner before his decease, by Mr. Chamberlaine. (See Rev. N. S. vol. xxv. p. 232.) We observe few additions in this volume which had not appeared before, except in the catalogue of Hogarth's prints. In the edition of 1782 of the Anecdotes of Painting, the first class of Hogarth's prints amounted to only 68: but in the present impression it is extended to 75. In class 3. comie and serious prints, we find 10 additional articles, and 22 additions since the former edition. At the end of this volume, we have six pages of addenda, not very interesting; being little more than a list of names of obscure artists, formerly subjoined to the Essay on Gardening. VOL. IV. The first article of this volume, which occupied the Vth volume of the Anecdotes of Painting, is the Catalogue of Engravers t. On a recent perusal of this tract, and of our account of it on its first appearance, it seems as if we then appreciatedits worth rather too hastily. Had this work been strictly what it professes to be, a mere catalogue, few besides general collectors of prints would have had patience to read it: but with the assistance of Vertue's memorandums, and Mr. Walpole's peculiar manner of relating anecdotes, it is rendered entertaining. We stumbled a little, however, at the threshold of this building, on reading the inscription over the door: When the monarch of Egypt erected those stupendous masses, the pyramids, for no other ufe but to record their names,' &c.-Had the author been living, we should have wished to ask him how he acquired the certain knowlege of the purpose for which the pyramids were erected? Two thousand years ago, it was a matter of doubt by whom or for what use they were built; and since that time, subsequent travellers, antient and modern, have thrown little light on the subject. M. Bailly, the great French astronomer, imagined them to be antediluvian. In p. 4. speaking of engraving on wood, vulgarly called "wooden cuts," the great improvement lately made in this art should have been mentioned by the editor, if omitted in the au thor's last revisal. Our noble author has taken great pains to display the merit of that worthy artist, Vertue: but engraving has See our Review, vol. xxx. p. 332. * P. 72. made nade such strides towards perfection in this country since his time, that the long list of his works, which occupies 25 pages, will interest few modern collectors, except such as have an indiscriminate rage for accumulation. At the end of the Catalogue of Engravers, we find a POSTSCRIPT to the 2d edition published in 1786.' As we do not remember to have seen this paper before, we shall here insert it: This volume, the Editor was sensible at its compilation, was the most imperfect part of Vertue's and his own accounts of The History and Progress of the Arts in England. It would not be difficult at present to give a much more complete deduction of the Graphic art in its different branches. But not only the indolence that attends age, and frequent illnesses, have indisposed the Author from enlarg ing his plan; more pardonable reasons determined him to make very few additions to this new edition; nor should he have thought of republishing the work, unless solicited by Mr. Dodsley. The indulgence of the public ought to imprint respect, not presumption; and instead of trespassing anew on that lenity, the Author has long feared he should be reproached, that Betinuit nostras numerosus Horatius aures; a quotation he should not dare to apply to himself, if adjectives in osus, as famosus, &c. were not most commonly used by Latian authors in a culpatory sense; and thus numerosus only means too volu minous. Another reason for not having enlarged the preceding work was, that it would interfere with the plan laid down of terminating the history of the arts at the couclusion of the last reign. In fact, a brighter æra has dawned on the manufacture of prints. They are become almost the favourite objects of collectors, and in some degree deserve that favour, and are certainly paid as if they did. Engraved landscapes have in point of delicacy reached unexampled beauty. A new species has also been created; I mean aqua-tirta-besides prints in various colours. Perhaps it would be worth while to melt down this volume, and new-cast.it, dividing the work into the several branches of wood-cuts, engravings, etchings, mezzotints, and aqua-tints. A compiler might be assisted by some new publications, as the Essays on Prints, Strutt's Dictionary of Engravers, and a recent History of the Art of Engraving in Mezzotinto, printed at Winchester, wherein are mentioned foreign notices on the arts. Were I of authority sufficient to name my successor, or could prevail on him to condescend to accept an office which he could execute with more taste and ability; from whose hands could the public receive so much information and pleasure as from the author of The Essay on Prints, and from the Tours, &c.? And when was the public ever instructed by the pen and pencil at once, with equal excellence in the style of both, but by Mr. Gilpin → The indentures, articles of agreement, grants, &c. to royal architects and artists, cited as vouchers in treating of royal and N 3 noble |