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the properties of acids, whose only claim consists in their power of combination with other bodies, and which power will, consistently with Berthollet's observation, equally entitle them to be ranked in the very opposite class of alkalies.

It will be readily granted that silica does not possess any one of the more obvious properties which characterize acids ; it is inodorous, tasteless, insoluble in water, or alcohol, does not affect vegetable colours, and has no immediate action upon any alkali, earth, or metal, so as to neutralize, dissolve, or form crystalline compounds with them. On the other hand, there are cases in which it appears to act as an alkali ; thus, in a finely divided state, silica is dissolved by the acids generally, and with the fluoric acid it forms a peculiar compound : it is certainly considered that the silicated fluoric acid is a compound acid, but. it is to be remembered that the fluoric acid possesses acidity without being combined with silica ; and moreover, when silicated fluoric acid is mixed with water, the silica is precipitated; but as this is perfectly analogous to what happens when muriate of antimony is poured into water, I think that analogies are more favourable to the alkaline, than to the acid properties of silica.

With respect to alumina, it cannot for a moment be questioned that its powers as a base are much more strongly marked than those of silica; it readily combines, when minutely divided, with almost every acid; and the formation of alum must be deemed satisfactory evidence of its saturating power with respect to acids.

Alumina, however, resembles silica in its property of combining with the alkalies, potash and soda ; and it is not, I believe, generally known, that with potash it so far performs the function of an acid, as to form a crystalline compound. I have, however, procured it in crystals of considerable size, and they appeared to be efflorescent, but I have not yet subjected them to analysis ; and as I am not aware that any crystalline compound of silica and potash has been formed, it must, I think, be admitted, that the acid, as well as the alkaline functions of alumina, are better defined than those of silica.

Oxide of lead is a substance which possesses the power of combining with acids and alkalies in a still more remarkable degree than alumina. When this oxide is dissolved in acetic acid, it is weil known that a certain quantity saturates the acid sufficiently to prevent its action upon vegetable colours, and by evaporation we procure sugar of lead; but if this solution be boiled with an additional quantity of oxide of lead, we obtain a compound (Goulard's extract of lead) which is remarkable on two accounts. First, it is a real subsalt, and soluble in water, and there is not, that I know of, a similar instance in record. Secondly, the oxide of lead in excess acts so completely as an

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alkali, that Mr. South has discovered, it possesses the power of turning turmeric paper brown. Again, Mr. Faraday informs me, that by boiling the solution of muriate of zinc, as usually obtained, with an additional quantity either of the metal or the oxide, a solution is produced, which acts on turmeric paper as an alkali. There cannot, therefore, be any doubt as to the power of oxide of lead and of oxide of zinc, to perform the function of an alkaline base.

The property which oxide of lead possesses of combining with the alkalies, potash and soda, or in other words, performing the function of an acid, is as perfect as that of silica; and it resembles alumina in forming a crystalline, and consequently a definite compound with an alkaline base. M. Berthollet, in the memoir already alluded to, states that when oxide of lead is boiled with lime water, very small iridescent and transparent crystals are formed. Now this compound is the more remarkable, because it results from the combination of two bodies, which possess distinctly marked alkaline properties. Similar observations may be made with regard to oxide of zinc; it combines with ammonia, potash, soda, and lime, and therefore appears to perform the functions of an acid even more extensively than oxide of lead.

The powder of Cassius is a compound which it would be difficult to describe, on the assumption that its formation depends upon the acid nature of one, and the alkaline nature of the other constituent. In fulminating gold, the metallic oxide appears to act as an acid, for it is in combination with ammonia ; but with the acids, the oxide of gold performs the function of a base, giving rise to the well-known salts of gold. Oxide of tin seems in some compounds to act as an acid ; thus it combines with the alkalies, potash and soda; and it also exhibits distinctly the properties of an alkali, as far as combining with acids is to be esteemed as such. If, however, the powder of Cassius be a compound of oxide of gold and oxide of tin, as is generally allowed, what functions can be attributed to them ? Do they combine as acids, as is supposed to be the case, when the fluósilicic acid is formed? or do they combine as alkalies, as when lime and oxide of lead unite? or if we consider one oxide as performing the function of an acid, and the other that of an alkali, what rule have we for assigning to each its peculiar office? These remarks might be extended to a greater length, especially if the oxides of antimony were taken into the account: these have been supposed by Berzelius to act the part of acids, and he has accordingly adopted the appellations of antimoniates and antimonites. There are many cases also in which metallic oxides combine with vegetable products, such as oxide of lead with gum, starch, &c.: now in these cases, the rules of nomenclature have been so completely set at defiance, and chemical propriety so violated, as to give these compounds the appellations of gummate and amylate of lead. Are we then to

consider gum and starch as acids because they combine with metallic oxides?

It would be difficult, or perhaps impossible to suggest any mode of describing such compounds, as I have adverted to, without incurring ambiguity or impropriety: I think, however, it would be possible to employ a nomenclature which would not involve the inconsistency of describing the same substance sometimes as an acid, and at others as an alkali. With this view I would propose to consider these compounds as resulting not from the same law as that which determines the combination of acids and alkalies, but as derived, at any rate, in most cases, from the general disposition which oxides have to combine with each other. By reverting to the original mode of expressing the compounds of silica and the alkalies, and alumina and the alkalies, we should avoid all theory, and employ terms: sufficiently descriptive of the compounds.

Instead, therefore, of speaking of silicates or aluminates, we may use the term silicated or aluminated potash, soda, or lime ; it may be convenient so far to regard the compounds as saline, as to consider the more distinctly marked alkaline body as the base, and without involving any theory. Thus oxide of tin possesses greater power of combination with alkaline bodies than oxide of gold does; the powder of Cassius may therefore be denominated stannated gold. Mercuriated lime, plumbated lime, antimoniated and antimonited potash, plumbated gum and zincated potash, are terms which may be employed without violating the present system of nomenclature, and without confounding bodies whose properties are not merely distinct, but diametrically opposite. The compounds of metallic oxides with ammonia might be included in this method; thus we might say cuprated or zincated ammonia; but as no ambiguity arises from the use of the term ammoniuret, it would be worse than useless to attempt any alteration in these cases.

ARTICLE XIII.

ANALYSES OF Books. An Historical and Descriptive Account of the Steam Engine,

comprising a general View of the various Modes of employing Elastic Vapour as a prime Mover in Mechanics; with an Appendix of Patents and Parliamentary Papers connected with the Subject. By Charles Frederick Partington, of the London Institution. 8vo. London, 1822.

The great importance of the steam engine in a commercial point of view will, perhaps, render it unnecessary for us to offer any thing in the way of apology for presenting our readers with a brief notice of this stupendous machine, of which a detailed account is given in the above work.

The historical data furnished by Mr. P. certainly throw considerable light upon the early history and subsequent improvements which have been effected in the steam engine, and to this part of the work we shall principally confine ourselves.

Among the numerous competitors for the honour of having first suggested steam as a moving power in mechanics, we must certainly place Brancas and the Marquis of Worcester in the foremost rank. The former of these was an Italian philosopher, of considerable eminence, and who, in 1629, published a treatise, entitled • La Machine,' &c. which contained a description of a machine for this purpose. The apparatus employed by Brancas was in fact nothing more than a large æolipile, similar to the blowpipe suggested by M.Pictet, of Geneva, with this difference, that the aperture in the pipe connected with the body of the æolipile instead of being directed towards the lamp. (or in this case the furnace that heated the machine) was made to strike against the floats or vanes of a wheel, by which means a rotatory motion was produced.'

“ After the publication of this scheme, which it is probable was never put in practice with any useful effect, nearly 30 years elapsed ere the further consideration of this important subject was resumed by the Marquis of Worcester. The mode of employing steam recommended by the Marquis, and which he describes in his • Century of Inventions' to have completely carried into effect, was entirely different from that of his predecessor; and it is evident that the noble author had received no previous hint of Brancas's invention, as he expressly states in another part of the above work, that he desired not to set down any other men's inventions ; ' and if he had in any case acted on them, to nominate likewise the inventor.' »*

“ In 1683, a scheme for raising water by the agency of steam was offered to the notice of Louis XIV. by an ingenious English mechanic of the name of Morland. This, however, was evidently

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* “ This work was written about the middle of the seventeenth century, and, consi. dered as the united discoveries of one individual, is certainly one of the most extraordi. nary scientific productions which has yet issued from the press in any age or nation. In addition, however, to its value, as containing the first tangible suggestion for the employment of steam as an hydraulic and preumatic force, it has unquestionably formed the foundation of a large portion of patent inventions which make so prominent a feature in the present day. The praiseworthy labours, however, of this indefatigable nobleman shared the fate which usually attends on projectors ; and it was left to the slow though certain march of scientific improvement to award to his memory a posthumous praise. The Marquis also published a work, entitled “ An Exact and True Definition of the most Stupendous Water-commanding Engine, invented by the Right Hon. (and deservedly to be praised and admired) Edward Somerset, Lord Marquis of Worcester, and by his lordship himself presented to his Most Excellent Majesty Charles II. our most gracious Sovereign.” This was published in a small quarto volume of only 22 pages, and consists of little more than an enumeration of the wonderful properties of the above engine ; and it is most probable that he never published any key to the first hint furnished in the Century of Inventions."

formed upon the plan previously furnished by the Marquis of Worcester in his Century of Inventions. Morland was presented to the French monarch in 1682, and in the course of the following year, his apparatus is said to have been actually exhibited at St. Germain's.

The claim lately made by the Americans to the invention of the steam boat is completely set at rest by reference to Mr. P.'s work, in which we find, under the head of Steam Navigation, p. 53, the following curious historical data :

“ In 1698 Savery recommended the use of paddle wheels similar to those now so generally employed in steam vessels, though without, in the remotest degree, alluding to his engine as a prime mover; and it is probable that he intended to employ the force of men or animals working at a winch for that purpose. About 40 years after the publication of this mode of propelling vessels, Mr. Jonathan Hulls obtained a patent for a vessel in which the paddle wheels were driven by an atmospheric engine of considerable power. In describing his mode of producing a force sufficient for towing of vessels and other purposes, the ingenious patentee says : In some convenient part of the tow boat, there is placed a vessel about two-thirds full of water, with the top close shut. This vessel being kept boiling, rarefies the water into steam: this steam being conveyed through a large pipe into a cylindrical vessel, and there condensed, makes a vacuum, which causes the weight of the atmosphere to press on this vessel, and so forces down a piston that is fitted into this cylindrical vessel in the same manner as in Mr. Newcomen's engine, with which he raises water by fire.

“Mr. Hull's patent is dated 1736, and he employed a crank to produce the rotatory motion of his paddle wheels ; and this ingenious inode of converting a reciprocating into a rotatory motion was afterwards recommended by the Abbé Arnal, Canon of Alais, in Languedoc, who, in 1781, proposed the crank for the purpose of turning paddle wheels in the navigation of lighters.”

Mr. Partington gives the following account of the improvements effected by Mr. Watt:

“ Mr. Watt's attention was first drawn to this subject by an examination of a small model of an atmospheric engine belonging to the University of Glasgow, which he had undertaken to repair. In the course of his experiments with it, he found the quantity of fuel and injection water it required, much greater in proportion than in the larger engines; and it occurred to him that this must be owing to the cylinder of this small model exposing a greater surface in proportion to its contents, than was effected by larger cylinders. This he endeavoured to remedy, by employing non-conducting substances for those parts of the engine which came in immediate contact with the steam. After a variety of experiments, the results of which we shall presently describe, he succeeded in constructing a working

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