Mechanics: The Science of Machinery

by A. Russell Bond

The next notable improvement in the phonograph was that of Emile Berliner, who in 1887 invented the laterally vibrating needle which cut a zigzag groove in the record instead of a hill-and-dale groove. In other words, instead of having his recording needle move in and out as in the Edison machine, it moved sidewise. He also invented the flat-disk record, which has almost completely supplanted the cylindrical record.

MACHINES THAT PICTURE MOTION

In a measure associated with the phonograph is the motion-picture machine, a machine with an eye and a retentive memory, which records on a sensitive retina a series of pictures that it is able to reproduce at any time. The recording of still photographs is remarkable enough in itself, but photography does not properly belong in a book on machinery. The taking of motion pictures, however, and the projection of these pictures upon the screen, involves the use of machinery, and we must refer to these machines briefly, owing to their widespread use at the present time.

Long years ago it was observed that when a picture is suddenly flashed before the eye an image is impressed upon the retina, which persists for a brief interval even after the picture itself has been withdrawn from view. By preparing a series of pictures of a figure which show it in progressive positions and flashing these pictures in rapid succession before the eye, persistence of vision will bridge the gaps between pictures and the figure will appear to move. This principle was first used as early as 1834 in an ingenious toy known as “zoetrope,” which consisted of a cardboard cylinder with a series of pictures drawn on the inner surface. There were slots cut in the cylinder through which these pictures on the opposite face of the cylinder could be seen. As the cylinder was revolved the eye caught only momentary glimpses of these pictures, one after the other, producing a sense of motion. In 1870, Henry Heyl of Philadelphia prepared a progressive series of photographs each separately posed before the camera. From these he made glass positives and projected them on a screen in rapid succession so that the picture appeared to move. In 1880, Edward Muybridge set up a battery of cameras and took a succession of instantaneous pictures of a galloping horse. The shutters were operated by strings stretched across the course and as these were successively snapped by the horse the pictures were progressively exposed. Glass positives of these pictures were thrown on the screen by means of a machine to which he gave the formidable name “zoöpraxiscope.”

INVENTION OF THE PHOTOGRAPHIC FILM

No one at that early date had thought of using anything but glass plates, and they were difficult to handle, both in the camera and in the projector. It was not until 1887 that the celluloid film was invented by Rev. Hannibal Goodwin, and then it became possible for Edison to invent a camera with a film that was intermittently moved so as to take a series of pictures. From the negative thus obtained a positive film was then made and placed in a machine known as a “kinetoscope.” Looking through a peephole in this machine the pictures were flashed before the eye in rapid succession. Finally, in 1893, C. Francis Jenkins, of Washington, developed a projector similar to those now in use by which the pictures could be thrown on a screen. Thus was born the motion-picture industry which has taken such a strong hold on the public.

It is now possible to project pictures in their natural color so as to add to their realism, but one more step is needed to give a sense of real life. The figures on the screen must talk as well as move. Efforts to combine the phonograph with motion pictures have so far been only partially successful. Perfect synchronism is very difficult to obtain, but it is highly probable that obstacles which hitherto have been most troublesome and seemingly insurmountable will, in time, be overcome. Then the “silent drama” will no longer be silent and we shall have “animated pictures” that will be really animated.

In addition to machines that talk we have machines that hear—machines that will respond to sound waves. A diaphragm flexed by sound waves closes an electric circuit and starts the operation of a machine. Some toys have been made which operate on this principle. Experiments have been made with a typewriter that will respond to a spoken message, but so far they have not been attended with much success. Boats have been built whose steering gear may be controlled by sound waves, but as yet nothing of commercial importance has been developed in machines controlled by sound.

MACHINES THAT SEE

Much more has been done with machines that see. There is a delicate device known as a “sun valve,” which is used on beacon lights so that as soon as it grows dark or very foggy the lamp is automatically lighted, and when the day dawns or light breaks through the fog the light is extinguished. The sun valve has two rods, one brightly polished and the other a dead black. Light and its attendant radiant heat waves are absorbed by the black rod, but are reflected from the bright rod. As a consequence, the black rod grows hotter than the polished rod and expands. The difference of expansion between the two rods is utilized to operate a valve which controls the supply of gas to the lamp. This valve is very sensitive and marvelously responsive to variations of light.