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yet upon the whole we cannot but admire the judgment and
ability displayed throughout the whole undertaking. It is
time however that we should proceed with our examination
of the volume.

We come now to the body of the original work; it com-
mences with a short introduction by the author, in which he
points out briefly the design of his treatise, and the nature of
those objects to which the blowpipe is applicable. This in-
valuable little instrument affords the means of readily trying
a vast number of experiments for determining the nature and
composition of different substances, and which though always
conducted on a microscopic scale, yet_present us in an
instant with the most decisive results. To the mineralogist
in particular it is of the most essential use ; for those employed
in such researches the present work is more immediately de.
signed, and after a full description of the apparatus, and the
methods of operating successfully, the author has given a
detailed account of the different characteristics discoverable
in each species of minerals when exposed to the action of
the blowpipe.

The treatise itself commences with an historical account of the use made of this instrument. It appears to have been long known and used in the arts before it was applied to scientific purposes. It appears to have been first employed in this way by Andrew Swab, a Swedish metallurgist, about 1733. The art of using the blowpipe was transmitted traditionally, and little published on the subject: indeed as the author remarks, as in other practical sciences, books alone are weak masters to make adepts in this. "The practical skill of Gahn in the use of this instrument was carried to greater perfection than that of any of his predecessorsmas an instance, it is mentioned, that long before the question was started whether the ashes of vegetables contain copper, Berzelius had himself seen him many times extract with the blowpipe from a quarter of a sheet of burnt paper, distinct particles of metallic copper. It was from this distinguished mineralogist that the author of the present work derived his skill.

“I was so fortunate as to enjoy a familiar intercourse with this eminent man, during the last ten years of his life. He spared no pains to impart to me all that he could from his knowledge and Jong experience, and I have strongly felt the obligation I then contracted towards the public to perpetuate as far as in me lies the fruits of his labours."

1

VOL. XIX. MAY, 1828.

This it appears Berzelius did in a former work on chemistry, but this was confined to an account of the use of the instrument. The results obtained by the application of it to mineral substances, it remained for our author to describe, from his own experiments; which he was strongly urged to do by Gabin, who had promised to criticize the results “bis blowpipe in his hand," had not the scheme been frustrated by his death.

Next comes a description of the blowpipe and the apparatus connected with the use of it. The author has detailed the various contrivances which have been proposed as improvements on it. The most complicated of which he rejects as absolutely useless, and considers the instrument in one of its most simple forms, as decidedly the best adapted to the purposes for which it is wanted. That of Dr. Wollaston is at once perfectly adequate to the production of the desired effects, extremely simple, and exceedingly portable. Persons unaccustomed to the instrument are apt to suppose that it requires great pulmonary exertion ; this however is quite a mistaken idea : it has notwithstanding led to several attempts to substitute for the action of the lungs, bellows and other contrivances : speaking of these our author remarks,

“ By these pretended improvements, motions more or less troublesome have been substituted for a slight exertion of the muscles of the cheeks, and their inventors have demonstrated by their very contrivances, that they did not know how to use the blowpipe: they might as well have proposed to play on a wind instrument with a bladder. Our conclusion must be that all apparatus of this kind is perfectly useless.” P. 18.

The notes by the translator form a very interesting and instructive appendage to the work. We will quote bis remark on the same subject of contrivances to supersede the action of the lungs.

« These expedients are like the various devices for lathes and tools for gentlemen turners and carpenters, who waste their time and cut their fingers in ineffectual attempts to make a box worth sixpence, with an apparatus that cost a hundred pounds. The skilful workman needs no such aids; and the operator with the blowpipe will do well to render himself independent of them at once.”' Note, p. 13.

There is however one instrument of this description which, as it answers purposes to which the common blowpipe is necessarily inadequate, the translator has thought it right to notice at some length in a note, p. 15. This is the apparatus called Brooke's or Newman's blowpipe, in which any gas or mixture of gases may be compressed with great force, and thus propelled through a jet; and in the case of a combustible mixture, the stream of gas itself being inflamed, the most intense heat is produced, so that the most refractory substances are fused in a very short tine. Of this and the other apparatus plates are given in outline.

The author next discusses the point of what combustible is best. The flame of a lamp is found better adapted than that of a candle for excitation by the blowpipe: though perhaps more inconvenient in travelling.

He then treats on the art of keeping up the blast and giving a proper direction to the flame. The translator, in a note, p. 21, sums up a whole page of directions to this effect, thus: “In fewer words, the operator must breathe through his nostrils, and blow with his mouth by the mere compression of the cheeks.” To produce a good heat requires some knowledge of flame and of its different parts. The author accordingly enters upon a description of flame, including the theory of the action of the blowpipe. This we consider one of the most able and interesting parts of the work ; and it is greatly enriched by an abstract of Sir H. Davy's account of the nature of flame, by the translator.

At the base of the flame of a candle, we may perceive a small part of a deep blue tint, and perfectly transparent. This forms the bottom of the flame, and terminates where the external surface begins to ascend perpendicularly. In the interior of the flame a dark part is seen through its brilliant covering. This space encloses the gases which issue from the wick, and which not yet being in contact with the air cannot undergo combustion. Round this space is the brilliant part of the flame, and a sort of thin covering may be perceived, slightly luminous, over this, thickest at the summit. It is in this outer part that the combustion of the gases is completed, and the heat the most intense. It is found that on inserting a very fine wire into a flame some remarkable appearances are observed, (for which we refer the curious reader to the work, p. 22.), which serve to indicate the relative temperature at different parts of the flame. These effects are found to be always greater just on the outside of the luminous part, and within the external part just spoken of; and they increase as we descend, keeping still in the same relative situation, till the wire comes upon the confines of the blue flame at the bottom. Here the maximum effect is produced. And it is upon this consideration that the operation of the blowpipe is conducted. By directing a stream of air against a tlame, the blue part is as it were driven into the interior of the flame, and terminating now in a point, instead of as before forming a circle round the flame, ihe effect is most intense at, or just beyond, that point. This effect is easily explicable on the principles of Sir H. Davy, deduced from a variety of experiments on explosive mixtures of gases. He has shown, that generally speaking the heat of a flame is greater, the more perfect the combustion of the inflammable matter while in a gaseous state. On the other hand the illuminating power results from an opposite cause ; namely, the decomposition of part of the gas towards the interior of the flame where the air is in the smallest quantity, and the deposition of solid charcoal, which, first by its ignition, and then by its combustion increases in a high degree the intensity of the light. This ke shewed very decisively by the simple experiment of placing a piece of wire gauze at a small distance above a stream of coal gas, and igniting it only above the gauze. The further he moved the gauze from the pipe the more air mixed with the gas, and the feebler was the light of the flame, while the heat proportionally increased ; as appeared from its effects in heating a fine wire of platinum. In a flame urged by a blowpipe at the point of the blue flame the greatest quantity of oxygen is sapplied to the gases issuing from the wick, and therefore at that point their combustion is more perfect, produces more heat and less light, whereas in the outer parts of the flame, where a solid product of charcoal is deposited in the form of smoke, the combustion is less perfeet, the heat less and the light greater.

Our author after giving several directions for obtaining a proper sort of flame, proceeds to describe the two principal operations in which the blowpipe is employed: these are the oxidation of metals, and the reduction of oxides. The account of these we will give in his own words. P. 28.

Oxidation ensues when we heat the subject under trial before the extreme point of the flame where all the combustible particles are soon saturated with oxygen : the farther we recede from the flame, the better the oxidation is effected, (provided we can keep up sufficient heat): too great a heat often produces a contrary effect, especially when the assay is supported by charcoal. Oxida. tion goes on most actively at an incipient red heat. The opening in the beak of the blowpipe must be larger for this kind of operation than in other cases.'

For reduction, a fine beak must be employed, and it must not be inserted too far into the flame of the lamp; by this means we obtain a more brilliant flame, the result of an imperfect combustion, whose particles as yet unconsumed, carry off the oxygen from the subject of experiment, which may be considered as being heated in a species of inflammable gas. If in this operation, the assay become covered with soot, it is a proof that the flame is too smoky, which considerably diminishes the effect of the blast. Formerly the blue flame was considered as the proper one for the reduction of oxides; but this idea is erroneous ; it is in reality the brilliant part of the flame which produces deoxidation: it must be directed on the assay, so as to surround it equally on all sides, and defend it from the contact of the air."

The substance on which the mineral to be examined is to be supported, comes next under discussion. Charcoal is, in most cases to he used; that of the lightest wood, and most free from cracks, and even-grained, is the best. In a note the translator recommends that from the alder. Supports of platina are also occasionally used with advantage. Sometimes the substance is to be placed in a glass tube flask, or mattrass. After this follows an enumeration of all the various implements, and articles of different descriptions which are useful in applying the blowpipe to mineralogical purposes. These descriptions, it appears bave been in some instances curtailed by the translator. Thus after an observation of the author, that order in the arrangement of the different instruments, &c. is very advantageous, the translator adds in a note,

6 Here follows a long detailed description of a table with a drawer at each side, and four in front, divided into moveable compartments of tinned iron to hold various instruments, &c. not forgetting a hook with a towel fixed to the right leg of the table. Next comes an equally elaborate description of a red morocco case to hold a travelling blowpipe apparatus.” P. 42.

The next section is devoted to the description of the different re-agents, or chemical tests, employed with the blowpipe, and directions for using them. These are few in number, and applicable in a great variety of cases, to assist in reducing oxides, and effecting fusion, and for other purposes connected with these. We sball not, however, attempt to give our readers any account of these processes. This section is closed by some general rules for conducting experiments with the blowpipe ; which display evidently the result of a minute practical acquaintance with all the varied forms under which these phenomena present themselves, and the various methods in which the different operations are performed; they will doubtless be found of infinite value to the young experimenter, and are given in a clear, simple,

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