New Modes of Attack.
Thus Helmholtz, at once a physician and a physicist, devised the ophthalmoscope, that simple instrument for observing the interior of the eye. On a plane less lofty an inventor’s success may turn on his width of outlook, his intimacy with fields remote from the home acre, so that he may gainfully ally two arts or processes that, to a casual glance, seem utterly unrelated or unrelatable. When a pneumatic tube between a post-office and a railroad station is obstructed, there would seem to be no promise of aid in a fire-arm. But snapping off its blank cartridge at the open end of the tube gives back an echo through the air within the tube; in measuring the interval between touching the trigger and hearing the echo, there is news as to where the tube is choked, the velocity of sound in air being known. From the labors of a postmaster let us turn to those of an apothecary, who pounds and grinds his drugs in a mortar which has descended from the day when it reduced grain to flour. The grindstones which succeeded the mortar were only in recent years ousted by Hungarian rollers of steel which separate the constituents of grain with a new perfection. Their excellence consists in imitating the crushing of the mortar, not in attempting the grinding of the familiar burrs.
The miller’s practice in one particular has given the postmaster a hint of value. In a flour-mill a cheap and sufficient motor is simple gravity as the products pass from one machine to the next. At the very outset the wheat is taken by conveyors to the top floor, whence its products descend, stage by stage, impelled by gravity alone, until the finished and barreled flour rolls into shipping rooms beside the railroad tracks. This principle has been adopted at the Chicago Post-office, where the mails as received are borne to the top floor, thence, by gravity, they take their way as sorted and re-sorted, to the ground floor where they are finally disposed of.
In a field somewhat parallel is the modern art of designing the layout of a great manufacturing plant so that the material shall travel as little as possible between its entrance and its exit. In a well planned ship-yard the machines are so placed that the steel plates, bars and girders, the planks and boards, move continuously from one machine to its neighbor, ending at last by reaching the building berth.
Shears for metal, cutting scissors-fashion, have long been familiar; the Pittsburg, Fort Wayne and Chicago Railroad employs the Murphy machine, on the same principle, to cut up old ties and bridge timbers intended for fuel. The upper moving blade is set about an inch out of line from the lower fixed blade, so as to allow spikes or bolts to pass through without injuring the machine. In dividing cord wood for stoves and furnaces a machine of this kind might be used instead of a saw.
It is by perfect means of subdivision that new and cheap materials for writing and printing are now produced. The leaves offered by the papyrus to scribes were used for centuries, so that the plant has given its name to paper now made from fibres of cotton, linen, or wood, finely divided, thoroughly mixed, and squeezed between rollers much as if paste. Paper from its smoothness, its absence of grain and its low price, is far preferable to papyrus leaves or vellum. Its manufacture has been copied in diverse new industries. Wood ground to powder, worked into pulp, molded into pails, tubs and the like, is saturated with oil to produce wares of indurated fibre. A pail thus manufactured will not split apart in dry weather when empty, or absorb liquids, and it is as easily kept clean as glass.
While wood has thus found a rival in pulp, stone has a new competitor much more formidable. Pavements and piers are often needed in long stretches, without joints for the admission of rain or frost. The demand is met by cements and concretes easily laid in unjointed miles. These materials when strengthened with skeletons of steel find many uses; a brief [survey] of them is given in this book. A sister product, terra cotta, baked at high temperatures, is now molded in beautiful designs not only for tiles, but as walls, cornices, finials, vases, hearths, and statuary.
Mergenthaler linotype, showing five double wedges for justification.