A History of Inventions, Discoveries, and Origins (Vol. 1&2). Johann Beckmann

Чтение книги онлайн.

СКАЧАТЬ that the following anecdotes of his life may prove not unacceptable to many readers. It was written by Professor Muller at Berlin, and transmitted to me by Dr. Bloch.

      Hohlfeld was born of poor parents at Hennerndorf in the mountains of Saxony, in 1711. He learned the trade of lace-making at Dresden, and early discovered a turn for mechanics by constructing various kinds of clocks. From Dresden he removed to Berlin to follow his occupation. As he was an excellent workman, and invented several machines for shortening his labour, he found sufficient time to indulge his inclination for mechanics; and he made there, at the same time that he pursued his usual business, air-guns and clocks.

      In the year 1748 he became acquainted with the celebrated Sulzer, at whose desire he undertook the construction of a machine for noting down any piece of music when played on a harpsichord. A machine of this kind had been before invented by Von Unger; but Hohlfeld, from a very imperfect description, completed one without any other assistance than that of his own genius. Of this machine, now in the possession of the Academy of Sciences at Berlin, Sulzer gave a figure, from which it was afterwards constructed in England. This ingenious piece of mechanism was universally approved, though several things may be wanting to render it complete; but no one was so generous as to indemnify the artist for his expenses, or to reward him for his labour.

      About the year 1756, the Prussian minister, Count de Podewils, took him into his service, chiefly for the purpose of constructing water-works in his magnificent gardens at Gusow. There he invented his well-known thrashing machine, and another for chopping straw more expeditiously. He also displayed his talent for invention by constructing an apparatus, which, being fastened to a carriage, indicates the revolutions made by the wheels. Such machines had been made before, but his far exceeded every thing of the kind. Having lost this machine by a fire, he invented another still simpler, which was so contrived as to be buckled between the spokes of the wheel. This piece of mechanism was in the possession of Sulzer, who used it on his tour, and found that it answered the intended purpose.

      In the year 1765, when the duke of Courland, then hereditary prince, resided at Berlin, he paid a visit to Hohlfeld, and endeavoured to prevail on him to go to Courland, by offering him a pension of 800 rix-dollars; but this ingenious man was so contented with his condition, and so attached to his friends, that he would not, merely for self-interest, quit Berlin. His refusal, however, obtained for him a pension of 150 dollars from the king.

Besides the before-mentioned machines, he constructed, occasionally, several useful models. Among these were a loom for weaving figured stuffs, so contrived that the weaver had no need of anything to shoot through the woof25; a pedometer for putting in the pocket; a convenient and simple bed for a sick person, which was of such a nature, that the patient, with the least effort, could at any time raise or lower the breast, and when necessary convert the bed into a stool; and a carriage so formed, that if the horses took fright or ran away, the person in it could, by a single push, loosen the pole and set them at liberty. The two last models have been lost.

      Every machine that this singular man saw, he altered and improved in the simplest manner. All his own instruments he made himself, and repaired them when damaged. But as he was fonder of inventing than of following the plans of others, he made them in such a manner that no one except himself could use them. Several of his improvements were, however, imitated by common workmen, though in a very clumsy manner. It is worthy of remark, that he never bestowed study upon anything; but when he had once conceived an idea, he immediately executed it. He comprehended in a moment whatever was proposed, and at the same time saw how it was to be accomplished. He could therefore tell in an instant whether a thing was practicable; if he thought it was not, no persuasion or offer of money could induce him to attempt it. He never pursued chimæras like those mechanics who have not had the benefit of education or instruction; and though this may be ascribed to the intercourse he had with great mathematicians and philosophers, there is every reason to believe that he would have equally guarded against them, even if he had not enjoyed that advantage. The same quickness of apprehension which he manifested in mechanics he showed also in other things. His observations on most subjects were judicious, and peculiar to himself; so that it may be said, without exaggeration, that he was born with a philosophical mind.

      A little before his death he had the pleasure of seeing a curious harpsichord he had made, which was purchased by his Prussian Majesty, and placed in an elegant apartment in the new palace at Potsdam. As he had for some time neglected this instrument, the too great attention which he bestowed on putting it in order contributed not a little to bring on that disease which at last proved fatal to him. His clock having become deranged during his illness, he could not be prevented, notwithstanding the admonition of his friend and physician Dr. Stahls, from repairing it. Close application occasioned some obstructions which were not observed till too late; and an inflammation taking place, he died in 1771, at the house of Count de Podewils, in the 60th year of his age.

      [The instrument now generally used in this country for measuring the distance gone over, is that invented by Mr. Payne, watchmaker, of Bond-street. In this ingenious contrivance motion is communicated from the traveller to the machinery of the pedometer, by means of a horizontal lever, which is furnished with a weight at one end and a pivot or axis at the other; under the lever is a spring, which keeps the lever when at rest close up to a regulating screw; the spring is so arranged as to be only just sufficiently strong to overcome the weight of the lever and to prevent its falling downwards.

When the body of the traveller is raised in progression, the lever is impelled downwards by the jerk, and immediately returned to its place by the spring, and so long as the motion is continued the lever is constantly in a state of vibration. A small ratchet-wheel is fixed to the axis of the lever, and beneath it is another and larger ratchet-wheel which fits on the same axis, but is not attached to it. These two wheels are connected by a ratchet or pale in such a manner, that when the lever falls, both wheels are moved forward one or more teeth, but when the lever rises again from the force of the spring, the larger ratchet-wheel is held stationary by a ratchet. The larger wheel is connected with a series of toothed wheels and pinions, by means of a pinion fixed on its under-surface. The centre wheel carries an index or hand, which points to figures on the dial-plate. The whole apparatus packs into the case of a watch26.]

      FOOTNOTES

15 C. 14. Nicolai, in the first part of his Travels, has translated this description of an odometer, and illustrated it with a figure by H. Catel.

16 This palace, with its ornaments, is described in the Memorie concernenti la citta di Urbino. Roma, 1724. fol. The figure to which I allude is in plate 53. Bernardino Baldi, the author of the descriptive part, considers it as an odometer.

17 In Joannis Fernelii Ambianatis Cosmotheoria, Parisiis 1528, we find only the following passage respecting this invention:—“Nec vulgi supputatione satiatus, vehiculum, quod Parisios recta via petebat, conscendi, in eoque residens tota via 17024 fere rotæ circumvolutiones collegi, vallibus et montibus ad equalitatem, quoad facultas nostra ferebat, redactis. Erat autem rotæ diameter.” In Almagesti novi parte posteriori, tomi primi, Bononiæ 1651. fol. the author, Riccioli, says that Fernel contrived his carriage in such a manner, that the revolutions of the wheels were shown by a hammer striking on a bell. Where that jesuit discovered this I cannot learn.

18 Doppelmayer, Nachricht von Nurnberg Künstlern, p. 82. Will, Nurnbergisches Gelehrten-Lexicon, iii. p. 156.

19 Cimelium Geographicum Tripartitum. Dresden, 1680.

СКАЧАТЬ