In the year 1745, John Frederic Unger, then land-bailiff and burgomaster of Einbec, and who is known by several learned works, fell upon the same invention without the smallest knowledge of the idea published in England. This invention however, owing to the variety of his occupations, he did not make known till the year 1752, when he transmitted a short account of it, accompanied with figures, to the Academy of Sciences at Berlin. The Academy highly approved of it, and it was soon celebrated in several gazettes, but a description of it was never printed.
A few days after Euler had read this paper of Unger’s before the Academy, M. Sulzer informed Hohlfeld of the invention, and advised him to exert his ingenuity in constructing such a machine. In two weeks this untaught mechanic, without having read Unger’s paper, and even without inspecting the figures, completed the machine, which Unger himself had not been able to execute through want of an artist capable of following his ideas.
Unger’s own description of his invention was printed, with copper-plates, at Brunswick, in the year 1774, together with the correspondence between him and Euler, and other documents. A description of Hohlfeld’s machine, illustrated with figures, was published after his death by Sulzer, in the new memoirs of the Academy of Berlin, 1771, under the title of ‘Description of a machine for noting down pieces of music as fast as they are played upon the harpsichord.’ Sulzer there remarks, that Hohlfeld had not followed the plan sketched out by Unger, and that the two machines differed in this—that Unger’s formed one piece with the harpsichord, while that of Hohlfeld could be applied to any harpsichord whatever.
When Dr. Burney visited Berlin, he was made acquainted with Hohlfeld’s machine by M. Marpurg; and has been so ungenerous, or rather unjust, as to say in his Musical Travels, that it is an English invention, and that it had been before fully described in the Philosophical Transactions. This falsehood M. Unger has sufficiently refuted. Without repeating his proofs, I shall here content myself with quoting his own words, in the following passage:—“How can Burney wish to deprive our ingenious Hohlfeld of the honour of being the sole author of that invention, and to make an Englishman share it with him, because our German happened to execute successfully what his countryman Creed only suggested? Such an attempt is as unjust in its consequences as it is dishonourable to the English nation and the English artists. When we reflect on the high estimation in which music is held in England, the liberality of the English nobility, and their readiness to spare no expenses in bringing forward any useful invention, a property peculiar to the English, it affords just matter of surprise that the English artists should have suffered themselves to be anticipated by a German journeyman lace-maker. To our Hohlfeld, therefore, will incontestably remain the lasting honour of having executed a German invention; and the Germans may contentedly wait to see whether Burney will find an English mechanic capable of constructing this machine, from the information given by his countryman Creed.”
FOOTNOTES
27 Phil. Trans. vol. xliv. p. ii. No. 483, p. 446.
REFINING GOLD AND SILVER ORE BY QUICKSILVER.
AMALGAMATION.
It is well known that quicksilver unites very readily with almost all metals, and when added in a considerable quantity forms with them a paste which can be kneaded, and which is called amalgam. On the other hand, as it does not unite with the earths, being a metallic substance, it furnishes an excellent medium for separating gold and silver from the substances with which they are found. The amalgam is squeezed through a piece of leather, in which these precious metals remain with a certain portion of the quicksilver; and the former are freed from the latter by means of fire, which volatilizes the mercury. This amalgam made with gold serves also for gilding metals (water-gilding)28, if it be rubbed over them, and afterwards heated till the quicksilver be driven off.
The first use of quicksilver is commonly reckoned a Spanish invention, discovered about the middle of the sixteenth century; but it appears from Pliny, that the ancients were acquainted with amalgam and its use, not only for separating gold and silver from earthy particles, but also for gilding29. Vitruvius describes the manner of recovering gold from cloth in which it has been interwoven. The cloth, he says, is to be put into an earthen vessel, and placed over the fire, in order that it may be burnt. The ashes are to be thrown into water, and quicksilver added to them. The latter attracts the particles of the gold, and unites with them. The water is then to be poured off, and the residue put into a piece of cloth; which being squeezed with the hands, the quicksilver, on account of its fluidity, oozes through the pores, and the gold is left pure in a compressed mass30. Isidore of Seville says also, that quicksilver is best preserved in vessels of glass, as it penetrates all other substances; and that without it neither silver nor brass can be gilded31. Modern mineralogists however have this advantage over the ancient, that they know how to separate the quicksilver from gold and silver without losing it. Instead of exposing the amalgam to an open fire, as formerly, and driving off the volatile metal, it is now put into a retort, and the quicksilver is collected in a receiver for further use.
Those also who wash gold from the sand found near rivers, use quicksilver before their work is completed; and I am strongly inclined to believe that this method prevailed in Germany long before the discovery of the mines in America. In the year 1582, John Michael Heberer described the washing of gold as he saw it practised at Selz, not far from Strasburg; and at that time quicksilver had been long employed for that purpose. In Treitlinger’s Dissertation, also, concerning the collecting of gold, and particularly in the Rhine, there is a description of the manner in which gold sand is washed by means of quicksilver, but no date is mentioned32.
The history of employing mercury in procuring the American silver is, as far as I know, most fully given by the Jesuit Acosta33, whose relation of the Indies abounds with curious and useful information. The quicksilver mines of Peru are situated in an extensive ridge of mountains near Guamanga, on the south side of Lima, and at no great distance from it. They are called Guancabelica, or Guancavilia. The mines were discovered about the year 1566 or 1567, when Castro was viceroy of Peru, by Henry Garces, or Graces, as he is called by the Portuguese. This man was a native of Porto, went to Peru in the Spanish service, and after the death of his wife became canon of the cathedral of Mexico. He translated the Lusiad of Camoens from the Portuguese into Spanish, and this has procured him a place in Professor Dieze’s translation of Velasquez’s History of Spanish Poetry. He caused a law to be enacted that no silver bullion should be suffered to circulate in Peru; but his greatest service was the discovery of the quicksilver mines. As he was one day examining the red earth, which the Indians use for paint, and call limpi, he observed that it was native cinnabar; and as he knew that quicksilver was extracted from it in Europe, he went to the place where it was dug up, made some experiments, and thus