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Thus whenever we please we may banish from all our manufactories the erroneous processes which operate to the detriment of their productions, and with substances de rived entirely from the soil of the republic, we may make earthen-ware at the same price, or even cheaper than that now made, which will give neither a disagreeable taste nor smell to victuals, which will be solid and salubrious, and will resist sudden transitions from heat to cold.

Description of a portable Thermometer, adapted to ascertain the Temperature of Wine-l'ats, and Dyeing-Coppers, and capable of being applied to various other Uses.

From the ANNALES DES ARTS.

WE are indebted to M. Regnier for the invention of

several kinds of metallic thermometers, the advantages of which are already acknowledged; he has likewise turned to account the extreme sensibility with which copper indicates the alterations of temperature. These thermometers are of different forms; that in general preferred is a tube of the above metal, into the inside of which is introduced a curved piece of iron or steel, the two ends of which are soldered, or otherwise attached to the extremity of the tube; a pinion, combined with this piece of metal, turns an index on the outside of the tube, the hand of which moves upon a portion of a graduated circle, for the purpose of indicating the contraction or expansion of the thermometer by cold or heat.

M. Regnier, by devoting his attention to the construction of a thermometer adapted to the operations of making

wine, contrived a portable thermometer, which he has presented to the Lyceum of Arts.

The tube and graduation of this instrument are the same as in the common thermometers; the mounting only exhibits a new arrangement proper for rendering it serviceable in agriculture and the arts.

The cane containing this thermometer is in the whole about a metre (three feet four inches) in length. The socket of this cane is of copper: it forms a long ferrule, which preserves the glass cylinder containing the liquid of the thermometer. The socket is pierced with several small holes, through which the fluid enters when the end of the cane is plunged into it, of course the liquor of the thermometer immediately receives the impression of the caloric, an advantage that is not possessed by the common thermometers for liquids, which are always too slow in their progress.

The iron end of the cane which rests upon the ground is supported at the extremity of the socket by a spring that yields when the end of the cane rests upon hard substances; and by this contrivance the thermometer is equally preserved from shocks on every kind of ground.

Another spring, placed immediately over the ball of the thermometer, yields when too much weight is borne upon the cane on a pavement, so that the prejudicial ef fects of every kind of shock or pressure are completely prevented by the disposition of the two springs.

The upper part of this cane is terminated by a ball of cork, covered with Morocco leather; the elasticity of the cork keeps the thermometer from breaking if the cane be accidentally dropped; but for the greater security a ribbon or string, to lay hold of, may be added.

In the centre of this cane a cavity is made, in which the tube of the thermometer is fixed, and half of its cir

cumference,

cumference, towards the top, opens with a hinge, for the purpose of making observations when the liquid of the tube is seen, and the scale graduated upon the ordinary. principles.

This opening shuts by means of two small hooks fixed in the wood; the thermometer then exhibits the appearance of a cane neatly varnished.

This new contrivance renders the thermometer oxtremely useful.

1. To ascertain and to compare at a certain depth the temperature of sown land, when the surface is hard frozen.

2. To estimate the heat of hay-stacks which sometimes take fire before the farmer is aware.

3. To compare the heat of garden-beds.

4. To find out the state of fermenting liquors: this thermometer will be the more useful for this purpose, as glass instruments sometimes employed for such observations are liable to break.

5. In the arts, for every kind of operation in which the heat of coppers is regulated to a certain degree.

Independent of objects of utility, this thermometer is an agreeable companion to the observer who, in his country-walks, wishes to ascertain and compare the temperature of different springs and streams, or any other similar purpose; and the convenience of being able to thrust it into various substances without breaking must be considered an additional recommendation.

On

On the Art of hardening Copper.

From the ANNALES DES ARTS.

COPPER in a state of purity and perfection is soft

and malleable; its tenacity is so great as to equal that of gold or iron. If copper be hammered cold for a long time, or more especially when it is flatted, it is found to acquire a still greater degree of hardness, but yet it is not capable of resisting violent pressure. If copper be made red-hot and suddenly plunged into water, instead of becoming hard it is rendered more flexible, and consequently softer than before. If copper be kept a long time in fusion, or be frequently melted by a brisk fire, without being covered with a flux or pulverized charcoal, it becomes brittle, unmalleable, and of course harder. But these qualities are corrected when copper is melted in contact with some carbonaceous substance. If melted copper be poured in water, as for the purpose of granulation, it is not, like steel, rendered harder by this operation.

If we reflect on all these facts proved by numerous experiments, we cannot but be astonished at the process employed by the ancients for hardening copper, of which most of their warlike instruments were made; though those implements of death are frequently mentioned by different writers, yet none of them has transmitted to us their method of hardening that metal. We have therefore been confined to conjectures on that subject; it has been conceived that copper could be hardened in the same manner as iron, and the same processes have, therefore, been employed. Their result, however, has only proved the ignorance of the operators of the principles of chemistry.

Thus

Thus the art of hardening copper has been reckoned among those that were known to our ancestors, but are now lost; but various circumstances and particularly researches made in ancient monuments have brought to light various articles, the composition of which has been investigated by analysis. This has shewn that the hardness of copper proceeded by no means from any introduction of charcoal into the mass, but from the mixture of another metal, which by its combination with the copper, augmented its hardness.

Mongez found that the composition of the pieces examined by him very much resembled that of bell-metal; he transmitted to Dizé a fragment of a copper dagger, the fracture of which proved that it was cast and not hammered. A solution of this instrument in nitric acid furnished a white precipitate, which was oxyd of tin; the copper was dissolved: this first experiment proved that the whole art of the ancients consisted in producing a combination of some other metal with the copper. The subsequent experiments of Dizé on Greek, Roman, and Gallic coins confirm this fact, the tin being found in these in the proportion of 24 per cent.

M. Hjelm, a Swedish gentleman, has lately turned his attention to this subject. He received of Professor Retzlis, of Lund, a piece of a two-edged dagger, which, together with some stone-cutter's chisels, was found in Sweden, where sabres perfectly entire are often discovered. This fragment was, externally, of a yellowish colour like brass; the edge was blunt; the fracture was granulated, and proved that the instrument had been cast: when tried with a file, this metal seemed by no means so hard as bell-metal, but harder than the brass employed for cannon. The surface of the part submitted to the file was of an orange-red colour, which soon turned to yellow,

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