A few years ago it was usual to attach pumps, dynamos, and other machinery to their actuating engines by pulleys and belts. To-day in most cases the connection is direct; all the energy which would be absorbed by intervening wheels and leather is saved. In steam-turbines one and the same shaft carries the steam-vanes and the armature of an electrical generator. In saw-mills of modern design a very long steam cylinder is provided with a piston directly attached to the saw carriage. The same principle gives high economy to the steam hammer and pile-driver of Nasmyth. Hammers, drills, cutters and other tools driven by compressed air are directly attached to the rod which holds the piston. In like manner Saunders’ channeling machine, actuated by steam, has its cutters attached to its piston, so that a blow is dealt with no intervening crank-shaft, lever or spring.
Direct, too, is the binding machine for magazines and cheap books, which simply stitches with wire the whole together at the back, as if so many thicknesses of cloth. With the same immediacy we have wall-papers printed directly from the oak or maple they are to represent. Indeed, veneers are now so cheap and good as to be used instead of paper as wall coverings. In the province of art Mr. Hubert Herkomer has accomplished a notable feat in the way of directness, dispensing with the camera, or any of the etcher’s preliminaries of biting or rocking. He paints in monochrome on a copper plate as he would on a panel or canvas, covers his painting with fine bronze powder to harden the surface, from which he then takes an electrotype.
A supreme feat of directness was the invention of a machine which relates itself to art, science and business, the phonograph. Forty years ago Faber constructed a talking machine of bellows to imitate the lungs, with an artificial throat, larynx, and lips affording a weird and faulty imitation of the voice. Edison, bidding sound-waves impress themselves directly on a plastic cylinder, reproduces human tones and other sounds with vastly better effect. Faber sought to copy the method of voice production. Edison set himself the task of taking tones as produced and making them impress a surface from which they can be repeated at will.
Contrivances Which Pay a Double Debt.
A lamp commonly used by camping parties, and well worthy of wider employment, is at once a source of heat and light; while it boils a kettle it sheds an ample beam upon one’s table or book. Just this union of two services may be found in the crude lamp of the Eskimo.
Many processes of manufacture once separate are now united with economy of time and power. Steam cylinders for mangling, ironing and surfacing paper, effect smoothing and drying at one operation. Green lumber for making furniture is bent and seasoned at the same time. Wire is tempered as drawn. At first reflectors were distinct from lamps; in an excellent form of [incandescent bulb] the upper part of the container is silvered, increasing the efficiency of reflection in decided measure, as shown on page 75.
Ascertaining Solid Contents.
Sometimes an indirect path is better than a direct course; or, as the sailors say: “The longest way round is the shortest way there.” We can readily measure the contents of solids which are regular or fairly regular of outline. It is easy to compute or estimate the contents of a stone as hewn by a mason to form part of a wall, but to find the volume of a rough boulder by direct measurement is too difficult a task to be worth while. Let us have recourse, then, to an indirect plan which goes back to Archimedes: it will remind us of how the casting process evades the toil of chipping or hammering a mass of metal into a desired form. We take a vessel of regular shape, preferably a cylinder, duly graduated, and partly fill it with water. Any solid, however irregular, immersed therein, will at once have its contents declared by the height to which the water rises in its container, the water-levels before and after the immersion being compared. Incidentally we here have a means of ascertaining specific gravities. Weigh this body before and during immersion; comparison of the two quantities will tell the specific gravity of the body, that is its density as compared with that of water. For example a mass of iron which in air weighs 7.75 pounds will in water weigh 6.75 pounds, so that the specific gravity of iron is 7.75, the difference between the two weights being unity.
Sometimes we wish to know the solid contents of a body which will not bear immersion in water; a mass of gum, for instance. In such a case we immerse the body in a graduated vessel filled with fine dry sand, carefully sifted free of hollow spaces. Both before and after immersion the sand is brought to a level which is carefully noted. The difference between these levels, measured in the graduations of the container, gives the solid contents of the immersed body.