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which the Peruvian mines are situated among the Cordilleras, as well as the seeming impracticability of conveying the parts of those large engines which would be required, over mountains inaccessible to any species of wheel-carriage.

"About to leave England in de spair of ever being able to accomplish his grand object, and passing by a street leading from Fitzroy square, he accidentally saw a model of a steam-engine exposed for sale in the shop of a Mr. Roland. He examined it with great attention; and, being struck with the simplicity and excellence of its principle and construction, he became its purchaser at a price of twenty guineas-this was the Trevithick model.

"M. Uvillé felt he now had in his hands the means, either of carrying forward his gigantic scheme, or of setting the fever of his mind at rest, by demonstrating the impossibility of achieving his project by the medium of the steam engine. He carried the model to Lima, and lost no time in trying its effects on the highest ridges of Pasco, which form the site of the mines: to his unspeakable joy the experiment succeeded to his most sanguine wish, and to that of some others who witnessed it; and in July 1812, he formed an association with Don Pedro Abadia and Don Jose Arismendi, opulent merchants of Lima, for the purpose of contracting with the proprietors of the flooded mines. The Marquess de Concordia, then Viceroy of Lima, highly approving the plan, under his protection the new company succeeded in getting contracts to work several of the principal mines for the payment of about a fourth part of the produce which they might bring to the surface. These contracts were made in August 1812; and in pursuance of his scheme, M. Uvillé again embarked for Europe, and reaching Jamaica, he took his passage for Falmouth. M. Uville's mind was too full of the flattering expectations which his scheme inspired, not to be

making frequent inquiries among his fellow passengers about mines and engines. One day conversing with a Mr. Teague, and expressing an anxious wish to find out, if possible, the author of the model he had carried to Lima, he was most agreeably surprised to hear Mr. Teague reply, Mr. Trevithick is my near relative, and within a few hours after our arri val at Falmouth I can bring you together.' It happened accordingly; and M. Uvillé resided several months at Camborne with Captain Trevithick, receiving during his stay instructions from that able man in mining and the management and construction of machinery, Accompanied by Capt. Trevithick, he visited other mining districts; and being introduced to Messrs. Bolton and Watt, the first steam engineers in the universe, he explained to these gentlemen the mountainous precipices to be sur mounted, and the great elevation of the mines above the level of the sea. But whether the objection of these gentlemen to engage in a speculation in which there was much uncertainty of carrying it forward with effect, either from the disturbed political state of Peru, or the difficulty of transporting the parts, or the great elevation of the situation being adverse to a fayourable employment of condensing engines, does not appear; but their opinion was unfavourable to M. Uvillé's project.

"Capt. Trevithick and his friend were not, however, to be discouraged from making the attempt; and in January 1814, the Captain entered into an engagement with M. Uville to provide nine engines, at a cost of about ten thousand pounds; which by very great exertions were shipped, with the permission of the British government, from Portsmouth, in the September following, accompanied by M. Uvillé and three Cornish men to direct the erection of the machinery. On arriving safely at Lima, they were welcomed by a royal salute and public rejoicings, But after they had got so far, so

great were the local obstacles in transporting the heavy masses across the mountains, that it was not till the middle of 1816 that they were able to set one of the engines to work. This was the first ever seen in South America, and excited intense curiosity. Great ceremony, it appears, was observed on this important occasion; and the most distinguished honours were conferred on the projectors by the vice-regal government. The official deputation appointed to superintend this new and very extraordinary operation, made a report to the viceroy, which was published in the Lima Gazette, in August 1816. Immense and incessant labours,' say the reporters, and boundless expense have conquered difficulties hitherto deemed insuperable; and we have, with unlimited admiration, witnessed the erection and astonishing operation of the first steam-engine. It is established in the royal mineral territory of Taüricocha, in the province of Tarma; and we have had the felicity of seeing the drain of the first shaft in the Santa Rosa mine, in the noble district of Pasco. We are ambitious of transmitting to posterity,' they continue, the details of an undertaking of such prodigious magnitude, from which we anticipate a torrent of silver that shall fill surrounding nations with astonishment."

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"They then go on to name a number of individuals on whom the eternal gratitude of all Spaniards is invoked;' and it is somewhat remarkable, that the only Englishman mentioned by name in this list of worthies is Mr. Bull.*

"While these operations were going on in Peru, Captain Trevithick in England was vigorously engaged in providing further supplies of steam-engines, construct ing coining apparatus for the Peruvian mint, and in constructing

* Mr. William Bull, of Chasewater, Cornwall, who was one of the three Cornishmen that accompanied M. Uvillé : Thomas Trevarthen, of Crowan, and Henry Vivian, of Camborne, were the

other two,

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furnaces for purifying silver ore by fusion; a project of incalculable importance from the increasing scarcity of quicksilver. This second supply was sent from England in October 1816, and arrived at Lima in the February following. Capt. Trevithick went out in this vessel. On his arrival he was immediately presented to the viceroy, and most graciously received, and his arrival officially announced in the Lima Gazette. Public notice was at the same time given in this of the completion of the second engine, said to be superior in power and beauty to the first; and also of the reception of some parcels of ore ofextraordinary richness, raised from the mines restored to use by the operation of these machines. The Gazette also announces the arrival of the other engines; ' but that,' it continues, which is of still greater importance, is the arrival of DON RICARDO TREVITHICK, an eminent professor of mechanics, machinery, and mineralogy, inventor and constructor of the engines of the last patent, and who directed in England the execution of the machinery now at work in Pasco. This professor, with the assistance of workmen who accompany him, can construct as many engines as shall be wanted in Peru, without the necessity of sending to Europe for any part of these vast machines. The excellent character of Don Ricardo, and his ardent desires to promote the interests of Peru, recommend him to the highest degree of public estimation, and make us hope that his arrival in this kingdom will form the epoch of its prosperity through the enjoyment of its internal riches, which could not be realized without such assistance; or if the British government had not permitted the exportation from England: an object hitherto deemed unattainable by all who know how jealous that nation is of all her superior inventions in the arts or industry.'

"So much importance was attached to Don Ricardo Trevithick's personal superintendence, that the

- viceroy ordered the lord warden of the mines to escort him with a guard of honour to the mining dis-> trict, where the news of his arrival in Peru caused the greatest rejoicings; and many of the chief men came to Lima, a distance of many days' journey over the mountains, to welcome him. M. Uvillé had written to his associates, that heaven had sent him out for the prosperity of the mines, and that the lord warden had proposed to erect his statue in massy silver.'"

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BRASS. An alloy of copper and zinc.

BRASSICA RUBRA, red cabbage. Its leaves exposed to boiling water make an excellent test for acids and alkalies. The dried leaves answer the same purpose.

BRAZIL WOOD. The wood of the casalpina crista, a tree which grows in the Brazils, and from which, by boiling, a fine red dye is extracted. BRIMSTONE, sulphur.

BRIONIA ALBA. A root formerly much used in medicine, and now known to consist almost wholly of starch.

BRITISH GUM is made by ex

posing starch to a temperature be tween 600° and 700°.

BRONZE. An alloy of copper, tin, and some other metals.

BRUCIA, brucine. A vegetable alkali, extracted from the bark of the false angustura.

BRUNSWICK GREEN. A muriate of copper and ammonia, used for painting.

BUTTER. The oily part of milk. BUTTER OF COCOA. An oily solid substance, firmer than suet, obtained from the cocoa nut, and used as an ingredient in pomatums.

CABBAGE, brassica rubra. Red cabbage is used to form a test paper.

CADMIA. The name which the ancients gave to some ore which is supposed to have contained zinc. CADMIUM. An undecompounded metal, first discovered in 1817.

CAFFEIN. A peculiar principle obtained from coffee. It is a very

delicate test for iron.

CAJEPUT OIL is obtained from the leaves of a tree found at Am

boyna and other Molucca islands.

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spondents could inform me the easiest method of making oxalie acid, in crystals, in a small way, say about one ounce. I have at tempted it, and cannot succeed, the residuum being flat, and similar to iodine crystals, but with all the taste of the oxalic acid.

I remain, Sir,
Your constant reader,

A YOUNG CHEMIST.

I should be also glad to know the easiest method of making a similar quantity of Epsom salts, and what causes their crystals to be so small; and if by any process they could be made larger in either the acid or salt.

CHEMISTRY AS A SCIENCE.

Art. XXIII.

GENERAL CHARACTERISTICS OF THE METALS.

In our last Number we brought to a close the account which we intended to give of the simple un decompounded substances.

But before we proceed to speak of light and heat, or what are usually called imponderable, and ought also to be called untangible, unseen substances, we shall present our readers with a tabular view of the characteristics of the metals. Not above seven metals were know to the ancients, but we have mentioned upwards of forty with which the moderns are acquainted. Some of them, indeed, have not been very accurately investigated, and it may hereafter perhaps turn out that they ought not to have a separate existence assigned them; but many have been thoroughly examined, and the existence of at least three times seven is established almost beyond the possibility of subsequent discoveries to annihilate it. It may possibly happen that a metallic principle or principles shall be discovered, such as the alchymists supposed might exist, and every individual metallic substance may be shown to be only some modification of it; but at present we have no right to assume

the existence of any such principle, and thus the forty-two metals must be considered as elementary substances. For the increase of our knowledge on this point we are entirely indebted to scientific chemists, and many of the metals have been discovered by means of the galvanic battery, which, in the hands of Sir Humphrey Davy and other eminent chemists, has, in a manner, given an entire new aspect to the science. The full powers of the instrument, and the laws of galvanism being as yet but imperfectly known, considerable alterations in our views may yet be anticipated. To give the reader an idea of the change which has already taken place, we may observe, that only a few years ago the entire crust of the earth was supposed to consist of a distinct species of bodies, to which the term earths was appropriated. So marked was the scientific dif ference, that Mr. Parkes, in his Chemical Catechism, observes, "If minerals had been placed on the surface of the globe, they would have occupied the greatest part of the earth, and have prevented its cultivation." Whatever scientific view may be taken of the nature of the substances on the surface of the globe, their fitness for the purposes of vegetation, and supplying man and animals with food, will remain unaltered; but it is now proved beyond a doubt, that these substances are minerals, and of that species of mineral which in general is most hostile to cultivation, namely, metals; but metals with such an affinity for oxygen, that "Volta's magical pile,” it has been observed, "directed by the genius of Davy, can only suspend for a moment the despotic sway of oxygen,-the emancipated metal soon relapses under its dominion.” So that oxygen, which we have already had occasion to describe as playing such an important part in all the phenomena of animal and vegetable life, is also the principle which gives fertility to the soil, and endows the, most barren and sterile substances with the quali

ties proper to supply us with food. In this circumstance, when it is recollected that this vivifying principle abounds in the atmosphere, there is probably as much to admire as in that distribution which has placed, as is remarked by Mr. Parkes, the metals having a less affinity for oxygen below the surface, while those which have an intense affinity form the exterior coat of the globe. That any utility can be derived from these discoveries of modern chemists is not at first very obvious. Already, however, the power of galvanism over the metals has been put to several important uses; and it certainly cannot be predicated with any certainty that the discovery of the metallic bases of all soils, and that oxygen is their vivifying principle, will never lead to some great improvement in the art of cultivation. Agricultural chemistry is scarcely yet born; and so much has been effected by chemical discoveries in other branches of art, that there is reason to expect, whenever they are applied to agriculture, greater wonders of production will be realized than the world has yet

seen.

We have to remark of the following table, that the statements are all taken from the works of Drs. Thompson and Ure. The tenacity of metals given, is from the former; and the figures signify the number of pounds weight required to break a metallic wire 0,078, of an inch in diameter. It may, too, be necessary also to explain to some of our youthful readers what is meant by SPECIFIC GRAVITY. They know that all bodies have a tendency to fall to the centre of the earth, which is called their weight. Different substances possess this tendency in different degrees; which seems, however, from some well known experiments with the air pump, to depend on the medium in which they are suspended, or through which they move. To ascertain the different weights of different substances, one medium must always be had recourse to; and as it is much easier to collect

the quantity of water a substance displaces, than the quantity of air, and thus determine the space it occupies; and as we only say one body is heavier than another, because its tendency to sink, or its weight, equals that of another body which occupies a larger space, water is the medium used for determining the specific gravity of bodies by chemists. Specific gravity, therefore, signifies the relative weight of a certain quantity of any body to a precisely similar quantity of water. As water itself, however, has weight, it is called 1.000, and the figures signifying specific gravities actually stand for this relative weight; and in addition thereto, if the body be heavier, 1.000 for the weight of the water, and if lighter, they stand for a sum less than that weight. The mode in which the specific gravities of bodies are determined is, to weigh them first in air, and then in water. In the latter case they lose weight precisely equal to the weight of their own bulk of water; and hence, by comparing its weight with the weight in air, we find their specific gravity, or their relation to the same bulk of water. The rule is to divide the total weight by the loss of weight in water, the quotient is the specific gravity. If it be a liquid, or a gas, it is weighed in a vessel of known capacity, and dividing that weight by the weight of the same bulk of water, the quotient is the specific gravity. Water is always taken at the temperature of 600 of Fahrenheit. In point of fact, therefore, the specific gravity of bodies, means only their weight in water, an additional 1.000 being added for the water. We are enabled by this method to make more accurate comparisons between different substances than we could by weighing them in air, but employing it gives us no positive addition to our knowledge. Platinum and potassium will be relatively heavy, whether weighed in air or water; and hydrogen still remains the lightest substance we know, whether compared with one or the other.

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