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surer to the government of Stora Kopporberg. He went to school at Westeras, and was afterwards •sent to the University of Upsala. His mind was early turned to scientific pursuits, witli a zeal which at once carried him rapidly forward, and made him study deeply as he went. While yet in the academy, he dropped a specimen of crystallized carbonate of lime, and the fall shattered it into fragments. By this accident the original nucleus of the crystal was developed, and Gahn, pursuing the idea which this suggested, and which would have been lost for any other person, succeeded, by cleavage, in extracting the rhomboid, which constitutes the primitive form of this mineral, from a great variety of secondary crystals. Bergman, to whom this observation and discovery were communicated, published, immediately afterwards, a dissertation on the forms of crystals, which called forth the wellmerited admiration of men of science. But while Bergman, says this author, reaped this honour from his essay, he had omitted to mention that it was the discovery of the pupil which bad furnished the basis of all the reasonings of the master. Bergman was distinguished for his candour ; he was as much beloved as admired; and we are rather slow to believe this questionable story of his observa'tions having been founded on the discovery of another, which he took care not to acknowledge. Gahn afterwards succeeded in analyzing the earth of bones, and in showing that it was phosphate of lime. The same substance, when occurring in,the mineral kingdom, has since baulked the efforts of analysts of considerable celebrity, and Gahn's success, therefore, reflects honour on his sagacity. The merit of this' discovery was attributed to Scheele, as it was first announced to the public in his works, without the name of Gahn being mentioned. The next thing in which he succeeded was to reduce manganese to a. metallic state; and though he is not now

deprived of the honour of having discovered this process, it was at first made known to the world by the works of Bergman. He next taught philosophers the scientific value of the blow-pipe, which, before his time, was only used by workmen, and drew up a concise summary of directions for its use, which were published in Berzelius's Elements of Chemistry. He was also the inventor of a balance, remarkable both for its extreme delicacy and the simplicity of the plan on which it is constructed, so that it can be made by any ordinary workman. In all these cases Gahn seems to have been so indifferent to celebrity, as to have made no effort to claim what was fairly his due. The author of the biographical memoir which we are now abridging, ascribes his unwillingness to come before the public, to a want of confidence in the value and completeness of his discoveries. He chose to revolve them again and again in his mind, and wished to submit them, according to the poets' rule, to the testof anine years' examination. Though this may probably have partly been his motive, we are willing to attribute his conduct to another cause. Those only1, we believe, are tenacious of celebrity who are destitute of tha't'thore solid enjoymenfwhich results from an active prosecution of the' business of life, and from energetically fulfilling the duties of a man and a citizen. 'Gahn was not 'a rtiere philosopher, deriving not drily celebrity, but perhaps even his' office, from his discoveries; he waS the active manager ahd conductor of several manufactories, and held a distinguished office in the political department of a free state. It" was probably from obtaining both advantage and honour from these two situations, that he was careless about that scientific celebrity1,11 to procure which'is the Object of so many intrigues, ancV so mudi'waiting by men who are'nothing'but philosophers; '"'"'"'''

Gahn's farther died wheti fae'was yourig; ahdleft'him'Ihnar^b^'clrcumstances, which compelled him to exert himself; and as he was destined to an employment about the mines, he took up his abode with the miners, and studied their practices till he had completely made himself master of all their knowledge. Having, in 1770, made his acquirements known, by an academic thesis on the improvement of iron foundries, he was soon afterwards appointed, by the College of Mines, to make experiments as to the melting of copper, at Fahlun. In consequence of his experiments, and by his recommendation, a new method of proceeding was immediately adopted, which saved a great deal of expense, and is followed to this day. He then acquired a part of the extensive works at Stora Kopporberg, where he settled as superintendent, and soon had an opportunity of obtaining wealth and adding to his reputation. During the American war, a sudden and a great demand was made for copper, and a very large order was sent to Fahlun, which Gahn, at his own risk, though others conceived it chimerical, undertook to complete. He succeeded, and not only added to his own wealth, butgained the increased confidence of all with whom he was connected. From the time of his first settling at Fahlun, in 1770, till 1785, Gahn took a deep interest in the improvement of all the chemical works of that neighbourhood; and, in conjunction with others, he established manufactories of sulphur, sulphuric acid, and red ochre, which were a source of great emolument to the proprietors. In 1780, the College of Mines, as a testimony of their sense of his exertions, bestowed on him a gold medal. In 1782, he received a royal patent as mining master; in 1784 he was elected a member of the Royal Academy of Sciences, at Stockholm; and inthesameycarhe was appointed Assessor in the Royal College of Mines. About the same period also he married Anna Maria Bergstrom, with whom he lived happily thirty-one years, and by whom he had one son and two daughters.

In 1773, he had been elected a chemical stipendiary to the Royal College of Mines; and from that time till 1814 every chemical problem the College had to decide was referred to him. In 1803 and 1804 a case occurred which evinced his skill. In consequence of the copper sheathing of a vessel having been corroded to a great extent, there^arose a prejudice against the Fahlun copper, and Gahn was appointed to ascertain if there were any' grounds for this prejudice. He demonstrated that the copper contained no pernicious ingredients, and it afterwards turned 'out that the copper of this vessel had not been obtained at Fahlun.

In 1778, Gahn began his political career, being in that year returned by the Mining Directory of Fahlun to the representative body of burghers. In the momentous discussions which took place in the Swedish Diet, in 1778, 1809, and 1810, Gahn took an active part, and was always a member of the constitutional committee. In 1795, he was chosen a member of the. committee for directing the general affairs of the kingdom. In 1810 and in 1812, he took an active part in the measures adopted for the maintenance of the poor, and for the promotion of agriculture.—. When it is considered that the mining district of Sweden which Gahn represented has long been distinguished for cherishing a love of freedom, that it has possessed numerous valuable privileges unchanged for ages, it is eulogium enough for Gahn to say, that his brother miners found in him a worthy representative, and a man adequate to the great trust reposed in him. It must be remembered that the period when he held this trust was one of peculiar delicacy and difficulty,—one when all the thrones of Europe were convulsed: and even Sweden felt the 'influence of that moral tempest which began at Paris. In this period of difficulty, Gahn acquitted himself with honour; and he is at this day as much endeared to his countrymen by the ardour and disinterestedness with which he defended their public rights as by his scientific improvements. Gahn, therefore, was a patriotic citizen, as well as a good man and a great chemical philosopher; anil enjoying the high honour acquired by the first of these characters, might well be careless of that scientific celebrity which it is the great object of all those who wonder at his carelessness to acquire. The end of Gahn was quiet and serene. His wife died about 1815, and from that time to 1818, his health, which had never been robust, visibly declined. In that year his decay was more rapid; he became weaker and weaker, and on the 8th of December, a calm and peaceful death terminated his' well-spent, and, we doubt not, happy life.

Such, we believe, is ever the end of such men; and those who delight, as we confess we do, to trace the beneficence of Nature, may read this character even in the manner by which she removes man from the scene of his enjoyments. She gradually blunts his perceptions, both of pleasure and of pain; she takes away one tie after another, loosening all his holds Of life so gently as to be imperceptible; and then she wraps him in the sleep of death, more quietly than ever baby was rocked to rest by the tenderest mother. This, we say, is her course, as exemplified in the end of men like Watt and Gahn.

— How calm their exit;

Night dews fall not more gently on the

ground; . Nor weary worn-out winds expire so . soft. Blair.

—But man, thwarting Nature,plunges into intemperance; he hurries to the field of blood; he lifts .the sword of vengeance, and sacrifices the prolonged happiness of life and the balmy quietness of, natural death to some erroneous theory of pleasure, some baneful prejudice, which has been palmed on him by ambition, or some absurd notion of crime and its retribution, which leads him madly in the same breath and by the same deed, both to applaud and punish the same crime.

. (To be continued.)

DICTIONARY OF CHEMISTRY.

Argentine Flowers Of AntiMony. An old name for anlimonious acid.

Argentum Vivum, quicksilver, mercury.

Argil, alumina,.

Argillaceous Earth. Anoiher name for alumina.

. Argillite, argillaceous schist us, clay-slate.

\ Arnica Montana. The flowers of this plant are employed in medicine.

Aromatics. Plants and other substances are so called when they have a fragrant and pungent taste &nd saiell. Their peculiarities appear to reside in an oil which, is distilled on" either with water er spirit.

Akrack. A spirituous liquor, manufactured from rice, and chiefly at Goa on the Malabar coast, and at Batavia.

Arragonite. A mineral so called from having been first found in Arragon.

Arseniate Of Potash. Aspects of carbonate of lime, the arsenical neutral salts of Macquer.

Arsekiates. Salts eortpoSeti of arsenic acid and a base.

Arsenic, A metal of a bluishwhite colour. What is called arsenic in commerce is a white'oxide of this metal, or arseidous acid'. ■"'"''

-acid. A combotiria'or

100 parts of arsenic and saiSaiW oxygen.

;" , Butter O*, ctitotiHiW

f SuLPHURET Of, ntflWar',

'Arsenious Acid. A conirJe&nd of 1Q0 parts arsenic and 34 parts oxygen; white arsenic.

Arsenites. Salts composed of arsenious acid and a b^se.

Arum Maculatum, wake robin, cuckoo point. Formerly used in bleaching.

AsAFffiTlDA, A well-known medicine. It is obtained from the foot of a large plant which grows in Persia. The root is cut, and the asafoetida issues in the^form of a thick juice, like cream,'wWcli becomes hard and of a browti'colour by exposure to ti^aif'. Tfi£

stench of this substance is so great, that the Persians are obliged to hire ships expressly for conveying it, as merchants will not take it on board vessels with any other species of cargo.

Asbestos, uibcslns. A silky-like1 mineral, of which there aie five varieties, thus named—amianthus, common asbestos, mountain leather, mountain cork or clastic asbestos, and mountain wood.

Ashes. In chemistry, as in common life, this term signifies what remains after combustion; but it is sometimes usual in chemistry to understand by it only what remains after vegetables have been burnt.

Aspabagin. A peculiar vegetable principle, which forms spontaneously in asparagus juice, when evaporated to the consistence of syrup. It is then in crystals.

Asphaltum, bitumen judaUum, Jews' pitch. At present bitumen is a name applied to a class of bodies, of which asphaltum is one. It is found in great abundance on the shores of the Dead Sea, in the island of Trinadad, in Albania, and in numerous other parts of the world. It is found soft on the shores of the Dead Sea; and it is supposed that originally it was all soft, and that it grows hard by exposure to the air. The asphaltum of the shops is said to be difl'erent from native asphaltum. The Egyptians employed it to embalm human bodies, and in old books it is distinguished by the name of mumia mineralis.

Assaying. The art of determining the quantity of precious metals in any mineral or metallic mixture, by analyzing a small portion of it. It is a particular branch of trade, and there is an Assay Muster to his Majesty's Mint, as well as numerous private assay masters. -..'•. i.

TO MAKE ICE IN THE MIDST

QF SUMMER. '\yfv. showed our readers, in our jas,t, dumber, a very easy method of, producing such a degree of cold asi even to.uceze mercury; ,and as that only takes place at a tehipera

ture considerably below the point where water freezes, they can, of course, easily freeze water in the midst of summer by the same means. There are, however, several other methods of accomplishing the same effects and as iced wine, iced fruits, and iced creams are great luxuries in summer, though an ice-house may not be at Land, we shall state some of these methods. Take eleven drachms of muriate of ammonia, ten of nitrate of potash, and sixteen of sulphate of soda. They should be recently crystallized, and contain as much as possible of the water of crystallization without being damp. Reduce each of these salts separately to a fine powder, and then mix them gradually in a vessel made of fine tin plate with five ounces of water; as the salts dissolve a degree of cold will be produoed sufficient to bring the thermometer below the freezing point. If a little water in a test tube be immersed in this mixture as the solution is going on, in about ten minutes it will be frozen. The vessel in which the mixture is made should be just large enough to contain it. Any thing, such as wine-bottles, jars containing conserves and fruits, lemonade for sick people, &c. immersed in this mixture, or moistened with it, and exposed to the action of a brisk current of air, may be rendered cold in the hottest day.

QUERIES.

To the Editor of the Chemist. Sir,—Can you inform me of a method of blueing steel equal to the blades of swords, and also of gilding it after it is blued 1 This will be of use to me.

I am, Sir,
Yours respectfully,
*> A. R.

, «♦,•

, : *«;*■■ • *•'■ t. ... (, July 1st.

•sir,—Ab/anSvv'er to the following queries, through the medium of The Chemist, will greatly oblige, A Constant Reader.

The best mode (if any) of extracting and preserving the juice of onions in a concentrated state?

[graphic]

From what kind of fat is the best tallow prepared; and what is the best method of preparing and purifying the same?

Sir,—A few days ago, whilst looking at some castings in an iron founder's yard, my attention was directed to a worn-out pot of considerable thickness. Upon inquiring the purpose to which a casting of sueh strength and dimensions was applied, I was informed, that it had been a.shot manufacturer's melting-pot; and that, notwithstanding its unusual thickness, (two inches in one part) it had not teen in use more than three months.

It appears, Sir, that these pots, when firmly set in brickwork, are employed in the preparation of an alloy of arsenic and lead, technically called temper, which is afterWards manufactured into shot. This composition is exposed to the temperature of ignition to effect a union of the two metals; but such had been the destructive agency of the mixture, aided fey the high temperature employed, that the side's of the iron pot were completely cut through.

Upon inquiry I have learned, that the injury is principally sustained at the surface edge of the melted alloy, and as the pot becomes destroyed on the upper circumference, smaller charges are necessarily thrown in until the vessel is incapable of holding a sufficiency of the mixture. Perceiving, Sir, that iris one of the objects of your xiii&A Publication to promote the fnrprtJVBtnient of the chemical manufactures of the kingdom, yon will permit ike, in furtherance of that dBfetrt, tt* propose the following questions::—Is the injury sustained by the' melting-pot occasioned by tile aJIoy acting on the iron, and thus forming a triple compound of arsenic, lead, and iron? Why is the'action of the alloy on the vesseP confined to the edge of the ffleffed tiompound only? Is the injury caused by any peculiarity jo

the cast iron of which the pot is made?- "~-.

I have little doubt, Sir, but what satisfactory answers to the above will be given, provided you deem this communication worthy the attention of the Chemist.

• J lam, Sir, \

Respectfully yours,

Arsenicum.
Chester, July 3.

EXTRAORDINARY ENGINE
FOR PROPELLING' VES-
SELS. ._ i-

A Mr. Samuel Brown has just constructed a very curious engine, to be employed as the actuating principle of machinery instead of the steam-engine. It is put into operation , by the agency of fire, water and air. It consists of many parts, and is not altogether free from complication; but at present we see nothing in its principles inimical to philosophy, and have no doubt itwill act, though as to its power and operating cost, as compared to the steam-engine, we have no very favourable opinion,^*-io?(don Journal of Arts and Sciences, ..

— — ^ •'<■ i Mih iiiiii.r

EXPLOSIVE ENGINE.

An engine of a-very remarkable kind is, we understand, about to be brought into public notice, which, if it answer the expectations of its inventor, may ultimately supersede the use of steam-engines. At the lower end of a small cylinder is placed a minute apparatus for oil gas. As the gas is generated it elevates a piston, so as to admit as much atmospheric air as, when combined with,{the. oil gas, will render the mixture explosive. When the piston-has reached this height the gas explodes, and the mechanical force of the explosion is employed to drive machinery. Experiments have, we understand, been actually made with this power, which was employed to force up water to a considerable height,— Edinburgh Journal of Science. \ < Jlk)^

Does tlUd afowle to Mr. Brewirtj

engine?""' '-' '•'■ I'ibun

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