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The art of navigation, though still crude, had by the 15th century so advanced that the sailor was no longer compelled to skirt the shore, with only rare ventures across open stretches of sea. The use of the compass, originating in China, had been learned from the Arabs by the crusaders, and is first mentioned in Europe towards the close of the 12th century. An Italian in England, describing a visit to the philosopher Roger Bacon in 1258, writes as follows: "Among other things he showed me an ugly black stone called a magnet ... upon which, if a needle be rubbed and afterward fastened to a straw so that it shall float upon the water, the needle will instantly turn toward the pole-star; though the night be never so dark, yet shall the mariner be able by the help of this needle to steer his course aright. But no master-mariner," he adds, "dares to use it lest he should fall under the imputation of being a magician." By the end of the 13th century, the compass was coming into general use; and when Columbus sailed he had an instrument divided as in later times into 360 degrees and 32 points, as well as a quadrant, sea-astrolabe, and other nautical devices. The astrolabe, an instrument for determining latitude by measuring the altitude of the sun or other heavenly body, was suspended from the finger by a ring and held upright at noon till the shadow of the sun passed the sights. The cross-staff, more frequently used for the same purpose by sailors of the time, was a simpler affair less affected by the ship's roll; it was held with the lower end of the cross-piece level with the horizon and the upper adjusted to a point on a line between the eye of the observer and the sun at the zenith. By these various means, the sailor could steer a fixed course and determine latitude.
124 visits
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Lime Boil.—In this operation, which is also known as bowking (Ger. beuchen), the pieces are first run through milk of lime contained in an ordinary washing machine and of such a strength that they take up about 4% of their weight of lime (CaO). They are then run over winches and guided through smooth porcelain rings (“pot-eyes”) into the kier, where they are evenly packed by boys who enter the vessel through the manhole at the top. It is of the greatest importance that the goods should be evenly packed, for, if channels or loosely-packed places are left, the liquor circulating through the kier, when boiling is subsequently in progress, will follow the line of least resistance, and the result is an uneven treatment. Of the numerous forms of kier in use, the injector kier is the one most generally adopted. This consists of an egg-ended cylindrical vessel constructed of stout boiler plate and shown in sectional elevation in the figure.
173 visits
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After bleaching, the cloth is next passed over a mechanical contrivance known as a “scutcher,” which opens it out from the rope form to its full breadth, and is then dried on a continuous drying machine. The figure shows the appearance and construction of an improved form of the horizontal drying machine, which is in more common use for piece goods than the vertical form.
173 visits
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In the modern processes of bleaching cotton pieces the lime boil is entirely dispensed with, its place being taken by a treatment in the kier with caustic soda (or a mixture of caustic soda and soda ash) and resin soap. The best known and probably the most widely practised of these processes is one which was worked out by the late M. Horace Koechlin in conjunction with Sir William Mather, and this differs from the old process not only in the sequence of the operations but also in the construction of the kier. This consists of a horizontal egg-ended cylinder.
156 visits
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The pieces are now run through a continuous washing machine, which is provided with a plentiful supply of water. The machine consists essentially of a wooden vat, over which there is a pair of heavy wooden (sycamore) bowls or squeezers. The pieces enter the machine at each end, as indicated by the arrows, and pass rapidly through the bowls down to the bottom of the vat over a loose roller, thence between the first pair of guide pegs through the bowls again, and travel thus in a spiral direction until they arrive at the middle of the machine, when they leave at the side opposite to that on which they entered. The same type of machine is used for liming, chemicking, and souring.
167 visits
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Portable Steam Engine, 1877. Portable steam engines provided belting power on farms to run threshing machines, circular saws, etc. This Frick model steam engine operated regularly from 1877 to 1949.
364 visits
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Edison with his Phonograph
In 1878 Mr Edison made a number of phonographs, which were exhibited in America and Europe, and attracted universal attention. The records were made in these on soft tinfoil sheets fastened around metal cylinders. For a while Mr Edison was compelled to suspend work on this invention, but soon returned to it and worked out the machine as it exists practically to-day. It occupies about the same space as a hand sewing-machine. A light tube of wax to slide on and off the cylinder is substituted for the tinfoil, which had been wrapped round it, and the indenting stylus is replaced by a minute engraving point. Under the varying pressure of the sound-waves, this point or knife cuts into the tube almost imperceptibly, the wax chiselled away wreathing off in very fine spirals before the edge of the little blade, as the cylinder travels under it. Each cylinder will receive about a thousand words. In the improved machine Mr Edison at first employed two diaphragms in 'spectacle' form, one to receive and the other to reproduce; but he has since combined these in a single efficient attachment.
687 visits
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Breech loading Gingal (Chamber out)
1173 visits
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Image 103
412 visits
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The string telephones which for several years have been flooding the boulevards and the streets of the different cities of Europe, and whose invention dates back, as we have seen, to the year 1667, are very interesting apparatuses by them themselves, and we are astonished that they did not appear rather in the physics cabinets. They consist of cylindrical-conical tubes of metal or cardboard, one end of which is closed by a stretched membrane of parchment, in the center of which is fixed by a knot the string or cord intended to bring them together. When two tubes of this kind are thus joined together and that the wire is tight, as shown, it suffices for a person to apply one of these tubes against the ear and for another person to speak very close to the opening of the other tube, so that all the words spoken by the latter are immediately transmitted to the other, and one can even converse in this manner in an almost low voice.
1197 visits
