LECTURES ON GOLD.

New Zealander, Volume 9, Issue 705, 15 January 1853, Page 2

LECTURES ON GOLD.

f At the suggestion of the council of the society i of Arts; it had been arranged to give in July last at the Museum of Practical Geology, Jennyn--strect, London, a course of lectures on gold, with a view, specially, to the instruction of emigrants about to proceed to Australia. The course wes to comprise six lectures, on the following subjects, by the following gentlemen The Geology of Australia, with'especial reference to ‘he Gold .Regions—by J. Bcete Jukes, M.A., i.G.S., of the Geological Survey, author of “ Sketches on the Physical Structure of Australia.” On our Knowledge of Australian Rocks as derived from there Organic Remains by Edward horbes, F.R.S. The Chemical Properties of Gold, and the mode of distinguishing it from other substances resembling it—by Lyon Playfair, GB., F.R.S.* Gold Mining and Washing—by W. VV. Smyth, M.A., F.G.S. The Metallurgical Treatment and Assaying of Gold Ores— by John Percy, M.D., F.R.S. The History and Statistics of Gold—by Robert Hunt, Keeper of Mining Records. Dr. Lyon Playfair’s Lecture—the third of the Series—excited especial interest, and is the only one of which we have met with a copious abstract in the papers. We transfer this to our columns, as, —now that New Zealand claims to be numbered amongst the auriferous countries, —it may be gratifying to many of our readers. The learned lecturer introduced his very able and interesting remarks by a reference to the mistakes which were continually occurring with reference to gold, and the necessity which consequently arose for accurate knowledge as to the mode of determining the character of the different descriptions of metals which might he submitted to the emigrant. The various modes of extracting and purifying the metal would, the lecturer said, devolve upon his colleagues in future lectures, his duty being simply to describe the general properties of the precious metal, and the mode by which it might he distinguished from the baser metals. Referring, in the first place, to the properties of gold, the lecturer stated that its unchangeableness, its lustre, and its colour, stamped it at once as the richest of metals. Its ductility was a point of considerable importance ; indeed, so ductile was it that it might be beaten out into thin leaves of only 1-282,000 of an inch thick ; and one grain of gold could be beaten out into a leaf of 5G| square inches, or might be di-awn into a wire of 500 feet in length. The density of this metal was also peculiar, its specific gravity being about times heavier than water. The colour of gold varied from the bright yellow in which it was found in the pure state, to blue, violet, black, and even green, when found in minute divisions. The degree of fusibility of gold was vcr} r high, and it consequently volatised very slowly. Having passed in review the physical properties of the metal, the learned lecturer next proceeded to review the chemical properties of gold. This metal, he said, was distinguished from all others by not being capable of being dissolved inaquafortis, its: only solvent being chlorine. The only modes by which gold could be dissolved were, by aqua regia, by chlorine, by sulphuric acid, and ordinary bleaching powder, and by common salt, saltpetre, and nitric acid, the solution thus formed'being tefchlofide of gold. Proceeding from the chemical properties of gold, the lecturer next described the various tests for this valuable metal. The first to which he called attention were those ordinarily adopted by goldsmiths, which, however, were somewhat fallacious ones—the touchstone and the nitric acid. One part of sulphate of iron—green vitriol—produced a precipitate, which was brown by reflected, and blue by transmitted light. So accurate, indeed, was this test that one part in 640,000 parts of water might be detected. Another mode of testing the metal was by salts of tin, or what was commonly known as the “ purple -of Cassius.” A small portion of common soda ash, added to the solution of gold, and boiled with an ordinary seidlitz powder, would produce u precipate of a black powder, which would clearly prove the presence of gold. Oxalic acid, tartaric acid, and soda, or other organic compounds, wqij|d also produce a black precipitate. Another mode referred to was. that of producing an amalgam with gold and mercury, and several very interesting illustrations were given of the affinity of gold for quicksilver, and the mercury flying off at a lower heat, leaving the gold behind, in a manner analogous to -that adopt ed in gilding. Xn search - ing for gold, however, the emigrant was advised not to overlook silver and platinum. The specific gravity of the first named metal was 10.4; it was soluble in nitric and sulphuric acid, and the simplest test was that of common salt. The specific gravity of platinum was 21.5; it was an exceedingly useful and valuable metal, and one which he would advise emigrants to look for. Like gold, it was soluble only in aqua regia, or solvents similar to those used in gold; the testa for it were sal-ammoniac or pearl ashes, or hydrochloric acid, tartrate of soda, and oxalic acid. Platinum was a metal which he had no doubt would be found to a considerable extent in Australia, and ho earnestly advised emigrants to look after it. The learned lecturer next proceeded to call attention to the substances popularly mistaken for gold, and which consisted principally of yellow mica, and of iron and copper pyrites. A mode of detecting iron pyrites was readily to be found in roasting the ore upon an iron shovel, when a smell of surphur would be given off, and the residue would assume the appearance of iron rust; or some of the powder placed upon a bright shilling, and heated over the flame of a candle* would produce the same disagreeable smell, and would also blacken the silver. Copper pyrites would easily dissolve in hydrochloric or nitric acid, and some iron nails or a piece of iron hoop, polished clean, and placed in the solution, would speedily be covered with a copper precipitate. Ammonia and prussiate of potasn were also infallible tests of copper pyrites. Yellow mica, the learned lecturer said, had frequently been mistaken for gold; but, with the exception of the colour, it possessed no property similar tothat of gold. An instance had recently occurred in which a captain of one of the guano vesselsfound a substance which he believed to be gold. The crew of the vessel took brooms and swept the substance into bags, and freighted the vessel with it. On arriving at Plymouth, two vendors of the precious metals went on board the vessel, and one of them, more cautious than the other, brought a sample of the cargo to the Museum of Practical Geology, to have it assayed. His companion, however, desirous of stealing a march upon him, went on board the vessel at midnight, and purchased the whole cargo, in which there was not a single ounce of gold—the biter being, therefore, bit in this instance. The learned Doctor also produced a box, which he said had been carefully forwarded to the institution, containing some specimens which were supposed to be gold, but which, upon analysis, turned out to be perfectly worthless. After having described in a very interesting manner the mode of conducting the a vet assay of quartz or sand supposed to contain portions of gold, the learned lecturer concluded his very able and interesting remarks as follows:—I have now endeavoured to impart to you the means by which you may recognise gold in doubtful cases, and I trust that the knowledge may occasionally prove useful. You are now called upon by one of the eventful periods which have, occured in the history of many nations, to people a land infinitely fertile in resources, impelled by * a desire to obtain by pursuing its direct representative The desire to attain gold, which caused so copious ft stream of emigration from America to California, and now produces so large a flow from this country to Australia, is only the repetition ofa desire which at all limes in human history has exerted a most important influence in the advance of civilization,

■md in the discovery and developemenl of neglected natural resources. This desire became the passionate madness of philosophers and of nations for a thousand years, and has left its records in the j history of alchemy. It passed over the world hke j an epidemic, leaving traces everywhere, but in j some countries became deeply rooted, and remained for centuries. The Arabians, when Bagdad, Bas- j go ra, and Damascus flourished as centres of com- ; mercial activity, hunted for gold by the labours of their philosophers, and kept up the desire tor | it by the reveries of their poets. Genu raised pa- i laces of gold, and the fruit trees produced only the precious metal. Gems of wonui out, price, an treasures of the noblest metal, were the icwai o their heroes and travellers, just at fire time when giants inherited our own countries, often attended bv little dwarfs, and, though bloody, cruel, and sagacious in the pursuit of their desires allowed themselves to be killed by the very simpJe devices of our most renowned giant-killeis. 1 hen Gc many revelled in her witches, who rode on broomstick! and sprites, whose mam occupation it was to fill hogsheads of the purest wine; while the rivers of France ran beauteous nymphs, immortals easily wedded to mortality. But in all countries, one after the other, giants, dwarfs, witches, sprites, and nymphs disappeared before the stern chase after "old. Chemistry recognizes that hergreatest discoveries arose in this pursuit, not directly but indirectly. The search after the transmutation of the baser metals into gold ledfo the discovery of a philosopher’s stone very different from that which occupied the attention oftheearlier alchemists. In the answers which Nature gave to the ill-denned and impulsive questionings of the alchemists, were apparent that the true philosopher’s stone consists, not in the direct discovery ot gold, but in the developement ot Nature’s laws, which enable us to add to the resources and happiness of the human race. The true philosopher’s stone of the alchemists was the science of chemistry which they created by their researches. By it we have # learned to add immensely to our comforts and enjoyments. Ihe earth now yields to us increased abundance in conditions where in absence of knowledge she would have proved unproductive. Metallic ores formerly unworkable are now reduced to metals absolutely necessary to our every-day comforts, more precious even than gold, ana which enable us to join the remotest par t of the earth by bands of constant communication. All countries are now found to have resources of immense importance to an ever-increasing civilization, and ihe sciences which can render them productive are the tine philosopher’s stone, changing base materials into gold. Depend upon it, then, your search after gold Is, as it has always hitherto proved, a means by which civilization will in the end be materially extended. But recollect that gold in itself is only an empirical representation of actual material wealth, which really consists in the full development of all natural resources. The only true method to ensure wealth will be that you neglect not the gifts which God has placed at your disposal. The country to which you intend to emigrate is fu‘l of natural resources, still very slightly developed. In a more thorough development of its agriculture, in the cultivation not ■only of wool and of tallow, but in the conversion of those nutritious parts of animals now thrown awav into excellent and portable food, there is much wealth to be obtained. There are many minerals there, less luring than gold, but more certain in there return, and are move useful to the every-day comfort of mankind. Recollect, then, that while we hail with pleasure, as all history justifies us in doing, the desire for gold which forces so strong a tide of emigration to Australia, history also tells us, that the consequent -good generally arises from collateral causes rather than from the one which produced thoorigina! impulse; and that, though disappointment will doubtless attend many of those who sec only the philosopher’s stone in the drifts and quartz ot the gold regions, those who read God’s teachings as displayed in nature will find a more sure way of transmuting valueless materials into gold by going out with the steady desire to improve and devdope the natural resources of their adopted home, in the firm belief that success will attend their efforts if they avail themselves of that knowledge of the Creator’s works which lie has permitted his creatures to attain, with a view to advance their comfort and happiness in this world. (Great applause.)