Obrazy na stronie

We next meet with the account of a fortification on one of the Cheviot mountains, named Yevering Bell. After which we are presented with a view of Kirk Newton, and the Castle of Copeland. Within a small distance of the latter, three battles were fought: one at Broomridge, another at Haltwell Sweine, and the third on the plains of Milfield, now a small village, but formerly the residence of the Saxon kings of Bernicia, after the death of Edwin.

The traveller afterwards entering Scotland, continues his route hy Kello, Roxburgh Castle, Dryburgh Abbey, and Mailross, all which he particularly describes.

The narrative of this Tour is enriched with original papers found among the manuscripts of the late Mr. Gale, as well as with engravings of many of the antiquities described. The whole is written in a clear, lively, and entertaining manner. Though we sometimes discover an naccuracy in the names of persons and places, Mr. Hutchinson appears to have paid a laudable attention to the various facts which he relates; and his descriptions may afford an adequate idea of the numerous antiquities in Northumberland.

A Manual of Chemistry, or a brief Account of the Operations of

Chemistry, and tbeir Products. Translated from the French of

M. Beaumé.. 12mo. 45. Jewed. Johnson. MR. Aikin, the trandator of this volume, informs us that

in some gentlemen who were going through a course of lectures in chemistry, to recommend to them such a book as might serve to retain in their memories the most important facts relative to this useful science. M. Beaumé's Manual de Chymie was doubtless well adapted to the purpose. It affords a con. cise view of the most effential subjects in chemistry, for the use of those who have passed through a regular course of lectures, and may likewise serve as a compendious fyftem to such as defire only to attain a general knowledge of the science. The several operations and processes in the art are introduced with so much of the theory as may elucidate the various principles on which they are founded, without perplexing the reader with the" more minute and abstract subjects of speculation.

After a short introduction, the author proceeds to give a general account of the elements or primitive principles of bodies, viz. fire, phlogiston, air, water, and earth; and afterwards treats of subitances faline, metallic, and earthy ; mi

neral heavier



neral and salt waters, with nitre, vegetable fubftances, animal substances, and the chemical principles of dying.

As a specimen at once of the translation, and the merit of the original, we fall present our readers with the doctrine relative to air.

• Air is an invisible, colourless, infipid, inodorous, weighty, elastic Auid, susceptible of rarefaction and condensation, and affecting none of our senses, unless it be that of the touch.

• This Avid environs the terrestrial globe, and ferves to fustain the life of the animals which exist on its surface. The experiments with the air-pump have fhewn that those animals which cease to breathe air immediately perish. • Air, as well as fire, is under iwo different states.

1. Pure, detached, and not making a part of any compound body: 2. combined with other fubstances, and serving as a prin. ciple or constituent part of many compound bodies, particularly of the vegetable and animal kingdoms.

We Thall first enumerate the most general properties of air in a pure and detached state.

Air is always fluid, like fire; at least to the present time, philosophers have not been able to render it folid, even by the aid of the highest degrees of artificial cold.

The fluidity of air is absolutely necessary for the support of animal and vegetable life. It would be extremely melancholy if this element, like water, were capable of beiąg rendered solid by moderate cold. Boerhaave conjectures that the Auidity of air may proceed from the particles of fire which are always mixed with it, and which are absolutely inseparable from is. The difficulty of producing a fufficient degree of cold is perhaps the oply cause why air has never been met with solid : it is a body which requires a very moderate degree of heat to keep is in the state of fluidity in which we are accustomed to find it.

• Air, as we have already said, cannot be perceived by the organ of sight: it is absolutely invisible, because colourless, It is likewise absolutely infipid and inodorous when perfectly pure ; bus it very readily becomes charged both with good and bad scents. When it is in agitation, it carries to considerable distances the odours with which it is impregnated : it seems even to be the reservoir of bodies which are in a fate of extreme divikon, and reduced to particles of as great teņuity as itself: for this reason it is difficult to find air perfectly free from foreign matters. It is always loaded with moiffure, which appears even to be essential to its use in respiration,

Next to, fire, air is the lightest matter with which we are acquainted. This is the cause of its always being on the furface of those bodies with which it is not combined. In general, it penetrates only into those places where it finds no fubitance

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heavier than itfelf. It is on this property of air that all the mechanism of furnaces, is founded.

* We might here enumerate a great number of experiments which prove not only the weight of the air, but its relation to the greatest part of known bodies; but for these thiggs, which appear ufeless in chemistry, we efer to the books of Natural Philosophy.

« Air is elaftic; that is to say, it yields to compresion, and returns to its former ftate as soon as the compreiing power is removed. It loses nothing of its elasticity, as oiber springy bodies do, either by being too much compressed, er kept too long in a state of compression. Air has been kept in a prodigiously comprefled ftate during fifteen or cwenty years, without the leait perceptible diminution of its elasticity.

• The effects of fire on air are to dilate or rarefy is, that is, to make it occupy a greater space than hefore. The greatest dilaration it can undergo from the most violent fire, is to thirteen or fourteen times its bulk. St can never be so far rarefied as to leave a perfect vacuum; a part of the air always remains, even when the containing vestel is brought to a white heat. We shall not relate the experiments proving this point; they may be read at large in the books of Natural Philosophy. When the air cools again, it is condensed, that is, its particles approach each other, so as to occupy no greater space than before.

• Air, as we have said, enters into the combination of many compound bodies, and even becomes one of their conftituent principles. When thus combined, it loses all its properties, and becomes what Dr. Hales terms solid air, that is, air rendered solid by afsimilating with animal and vegetable bodies *


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The air which thus becomes a principle of-bodies, not only during the time of its combination has different properties from common air, but after its separation appears with different qualities. This kind of air, termed fixed or fixable, contrary to the atmospherical, is destructive to light and flame. It easily combines with water, and gives it an acid impregnation. It is separated from bodies in all fermentative and effervescent processes, and in some cases by calcination. It seems not yet clearly determined whether this is a different species of air from the atmospherical, or only a part of it; though the latter opinion appears most pro: bable.

• Dr. Priestley, who has added more to the knowledge of aerial bodies than all his predecessors in this part of chemiltry, has at length discovered, that the purelt common air offered us by nature is not a simple body, or chemical element, but is itself a compound. Its constituent parts, according to him, are " nitrous acid and earth, with ló much pologiston as is neceifary to its elasticity, and also to bring it from its state of perfect purity to the mean


• Perhaps air does not enter into the composition of bodies till it is united with some principle as yet unknown to us. In this case it would exist there under the form of a secondary principle, as fire under that of phlogiston. However this bé, we ought to make a proper distinction between'this combined air, and that which is interposed between the particles of bodies. The latter may be separated by mechani means; whereas the former can only be expelled from bodies by de. composing them.

• Boerhaave on this subject says, that an insulated particle of air is not elastic, and that it acquires this property only when it is united with others; which takes place by the union of those particles of air which are detached from bodies submitted to a chemical analysis.

• We thall not undertake at present to demonstrate the existence of air as performing the function of a principle in vegetable and animal bodies. This would engage us in details which would suppose the knowledge of a great number of things that must be first treated of. We have just considered the effects of fre upon air; let us now examine those of air

• Air is the vehicle of combution. Without it no combustible bodies can be burned: they are even extinguished though well kindled when all communication with the external air is cut off. Many able philosophers imagine that the weight and elafticity of air are the only causes which render it proper for keeping up combustion. By means of these properties, it unites and assembles the active fire, and applies it immediately to the combustible matters which remain to be burned.

• This theory appears insufficient for the explanation of the following phenomenon. Black charcoal is put into a box of iron or earth exactly closed; this is placed in a furnace and hoated to a white heat. How violent and how long continued soever the heat is, it is found, after the box is cooled, that the charcoal has loft nothing of its weight, and that it has undergone no combustion. It is, however, certain, that the matter of fire, in its igneous motion, has continually been very intimately applied to it, and that the inflammable matter of the charcoal itself has been in a kindled state.

• It may be conjectured with a good deal of probability, that the charcoal in this experiment does not burn, because it is deprived of air, and of all those matters which perform the office of air in becoming considerably rarefied on numerous

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condition in which we find it." He has accordingly, by means of the nitrous acid and a pure earth, free from phlogiston, produced an artificial air of much greater purity than the atmospherical. This he terms dephlogisticated air. See Experiments and Observations on Air, vol. ii. lect. 3. J. A.'

occasions, occasions, but which cannot be volatilised in close vessels. The inflammable matter in charcoal is not susceptible of any dilatation; it is even, as we have remarked, more fie to absorb air during its combustion, than to furnith it. The charcoal in this process is penetrated with fire, but a fire foreign to it. Its own inflammable maiter does not consume, because it is incapable of dilatation.

• It will be urged, that neither do vegetable or animal bodies, though containing much air, with oily and aqueous mat. ters, &c. burn during their analysis; but this is owing to the fire being raised by degrees, in order to detach these fublancès in fucceffion. Experience has fewn, that when the fire is pushed hastily, explosions are occafioned, which may arise as well from the infanmarion, as the dilatation, of these volatile parts.

• From what has been said, it evidently follows, that the concourse of the air is absolutely necessary for the combustion of bodies. It is upon this property that all the mechanism and construction of furnaces is founded.'

In tranflating this Manual Mr. Aikin has acquitted himself with his usual ability, and performed an acceptable service to the lovers of chemical knowledge.

Discourses on the Four Gospels, chiefly with Regard to the peculiar

Design of each, and the Order and Places in which they were Written. By Thomas Townson, B. D. 410.75. 6d. in boards.

Bathurst, THE "HE learned author divides this work into eight discourses.

In the first he gives us a general account of the peculiar design of each gospel, the late of the church to which it was adapted, and the charaders of the evangelists.

In the second he proves, on the authority of ancient writers, 1. That St. Matthew was the first writer of a gospel; that he composed it early for the instruction of the Jewish people, and published it in Judæa. 2. That St. Mark was the second evangelist ; that his gospel was revised or even dictated by St. Peter; that it was compiled for a mixed society of Jewish and Gentile converis; and most probably published at Rome, or in Italy. 3. That the next evangelist, St. Luke, wrote with a more peculiar view to the converted Gentiles, and, as it seems likely, in Achaia. 4. That St. John wrote his gospel after the destruction of Jerusalem, in Asia Minor.

In the third discourse the author shews, by a great variety of parallel passages, that each foregoing gospel was known to the following evangelists. VOL. XLVI. Augufi, 1778.


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