Knight's cyclopædia of the industry of all nations, 1851 / [edited by George Dodd].

Date:
[1851]
Catalogue details

Licence: Public Domain Mark

Credit: Knight's cyclopædia of the industry of all nations, 1851 / [edited by George Dodd]. Source: Wellcome Collection.

    945/1000
    stances, whether of scarcity of employtaelit, of isolated situation, or of combination among masters in the same bitsmess, or through ad extensive district, -which place the workman more or less at the mercy of his employer, the payment of wages in ti'uok may be, and continually has been, and is still extensively, used for the defrauding and oppressing of workmen. TRUMPET. Tins musical instrument is of the highest antiquity. It is a single tube eight feet long, less in diameter than the horn, doubled up in a parabolic form, sounded by means of a mouthpiece, and subject to the same acoustical laws which govern all instru- ments of this class. [Hoen.] The natural scale of the trumpet extends to about twenty notes ; but by the assistance of a smaU brass tube, called the tuning-pipe, or shank, by which the tube of the ti-umpet is lengthened, the number of notes may be increased. MUsio for the trimipet, as in the instance of the horn, is always written in the natural key of o, and the key to which the instrument is to be adapted is pointed out by the composer. TRUSSING, The rods or bars which are added to a gkder for the purpose of trussing or supporting it may be applied in two sets, one on each side of the girder, and connected together by short cross-pieces at the necessary points ; or the beam or girder itself may be divided longitudinally into two halves, or flitches, separated just so far as to admit a single truss between them, and held in the right position by the insertion of small blocks. One of the simplest methods of trussing girders is that in which the beam rests upon walls at its extremities, and has two inclined struts, resting on notches in the timber at the lower end, and supported at the centre or junction by a vertical kingpost, screwed by a nut beneath the beam. This form is improved by connecting the lower ends of the inclined bars by an iron rod stretching in a perfectly straight line, and capable of being brought to any required degree of tension by means of screws or keys. Cast-iron beams are frequently trussed with wrought-iron rods, in a similar manner to those of wood, and are applied to purposes for which great strength is required. TUBES. Under the heading of PrPBS is given a short notice of the different modes of making tubes, pipes, cylinders, and barrels, according to the nature of the material em- ployed and the purposes to which the articles are to be applied. Mr. Hick has recently invented a contrivance for making taper tubes; that is, tubes which taper or diminish in dia- meter from one end to the other, The tubes are first made parallel or oylindrioal, and are tapered afterwards. The machino employed efi'ects this by excentrio grooved roUors: a greater or less degree of taper being obtained by varying the proportion between the rate at which the tube is drawn through the machine and that at which the rollers revolve. TUBULAR BRIDGE. [MenaiBhidges.] TUMBREL, or TUMBRIL, was the name of a machine formttly used for the punish- ment of scolding women, consisting of a stool or chair attached to the end of a long polej mounted in such a manner that the chair, with the offender placed in it, might be swung over a pond, and immersed as often as might be necessary. The tumbrel was also used as a punishment for brewers and bakers who trans- gressed the laws relating to them. The name is also applied to the covered carts used to carry tools, (fee, in a train of ai'tillery» TUN. [Ton.] TUNGSTEN. This metal was first ob- tained in a perfect state by M. d'Elhuyart, in 1781. The name is formed of the Swedish words tungsten,' heavy stone.' It has a grayish- white colour and considerable lustre. It is brittle, and nearly as hard as steel. Its specific gravity is 17.4, and with the exception of platina, gold, and iridium, is the heaviest known metal. It requires a very high tem- peratui'e for fusion. It is not altered by ex- posure to the air. When heated to redness in the open air it takes fire, combines with oxygen, and is converted into tungstic acid. Nitric acid produces the same effect. The chief minerals which contain tungsten are Tungstic Acid, or Schcelic Acid; Tung- state of Lime; Wolfram, or Tungstaie of Iron and Magnesia; and Tungstate of Lead. Tungsten combines mth several of the simple substances ; but the compounds have not yet been appUed to many useful purposes. TUNING FORK. In tuning the notes of a musical instrument, such as the pianoforte, the first point is to fix upon some one note, by the pitch of which all others may be de- termined. The only way of retaining a per- manent pitch for use is by having an instru- ment which time will not alter. A standard pitch is usually obtained, or professed to be obtained, by the tuning fork, an instrument consisting of two steel prongs extending from a steel handle. When these prongs are sharply struck they vibrate, and if the insti-u- ment be then held to the ear, or placed upon the flap of a table, or any other sound board, a low and very pure sound is heai-d, if the prongs be perfectly equal. Theso tuning forks are usually made to sound either o or a, and they would answer their purpose exceedingly