The degree in which a crystal, or a particular kind of glass, bends a beam of light is usually measured by giving the crystal or glass the form of a prism, through which rays are sent. Sometimes a crystal is so small and irregular that this method is not feasible. Then the inquirer resorts to an indirect plan. He immerses the crystal in liquids which he mixes until the crystal disappears through ceasing to bend light differently from the surrounding bath. He then fills a hollow glass prism with this liquid, and in noting its refraction he learns that of the immersed crystal.
Blenkinsop’s locomotive, 1811.
Middleton Colliery, near Leeds, England.
Omission of Needless Elements.
A fresh eye, with a keen brain behind it, often detects wasted work in a process long sanctioned by tradition. At the Tamarac Copper Mine, in Northern Michigan, some new ore-crushers were needed in 1891. Among the engineers who sought to furnish these machines was Mr. Edwin Reynolds, of Milwaukee, whose improvements of the Corliss engine have made him famous. That he might see ore-crushers at work for the first time in his life, he visited the Tamarac mine. He observed that the stamps were built on an immense bed of costly timbers and rubber sheets, supposed to be indispensable to efficiency. His eye, unwarped by harmful familiarity, utterly condemned this elastic foundation. He at once proposed to discard both timbers and rubber, and rear new crushers directly on a vast block of solid iron. This heresy quite shocked the directors of the Tamarac Company; they stood out against Mr. Reynolds’ plan for two years. Then, with profound misgivings, they allowed him to erect a stamp of the cheap and simple pattern he had suggested, so laying the iron bed that, in case of its expected failure, work would be delayed not more than two days. Up went the Reynolds’ stamp, and out poured sixty per cent. more crushed ore than from a preceding machine using the same power. Instant by instant its energy was wholly exerted in crushing rock, not largely in the useless compression of an enormous elastic bed.
Long before there was any Tamarac Mine, inventors had bothered themselves providing for difficulties as imaginary as those which, at vast outlay, were met by the timber underpinning of old-time ore stamps. In 1825 the builders of locomotives at Easton, in England, provided their engine-wheels with teeth which worked into racks with corresponding projections. They were afraid that a smooth wheel on a smooth track would slip without onward motion. Their unnecessary gear was discarded when it was found that under a heavy engine a smooth wheel has adequate adhesion on a rail as smooth as itself. Toothed wheels and racks are now only at work on the railroads of Mount Washington and other steep acclivities. As James Watt used to say to William Murdock, his trusted lieutenant,—“It is a great thing to know what to do without. We must have a book of blots—things to be scratched out.”
Printers Abandon Useless Work.
Daily newspapers in part owe their cheapness to an omission that at first seemed bold enough. For many years printing paper, made in continuous rolls each of a mile or more, used to be cut into sheets, fed one by one to the press. It was a long stride in economy when the printer left the roll alone, and let an automatic press feed itself from the unwinding paper, cutting off a sheet only after the printing.
Electricity Used as Produced.
A parallel example is recorded in the twin art of telegraphy. At first it was believed that two wires were indispensable for a circuit. Steinheil showed that a single wire suffices if its terminals are soldered into plates buried in the ground. Thus, at a stroke, by impressing the earth into the service of electrical communication, he reduced the cost of telegraphic lines by one half. In another field the electrician has given himself a good deal of trouble in vain. As it originally streamed from voltaic batteries, the electric current had always a single direction; it was, to use a familiar phrase, a direct current. But when Faraday invented the first dynamo, and produced electricity from mechanical motion instead of from more costly chemical energy, the current was not direct but alternating; that is, its pulses came at one instant from the positive pole, the next instant from the negative. Inventors took great pains in devising apparatus to convert these alternating pulses into a direct current such as that yielded by a voltaic battery. To-day the alternating current for many important purposes, including transportation, is employed just as it leaves the dynamo. Such a current usually has comparatively high tension, at which transmission is much more economical than at low tension, small conductors serving instead of large ones. This advantage in many cases more than offsets the loss entailed by reversal of the magnetic field at each alternation; a loss but small when iron for the electro-magnets is well chosen.