What Causes an Echo?
An echo is caused by the reflection of sound waves at some moderately even surface, such as the wall of a building. The waves of sound on meeting the surface are turned back in their course, according to the same laws that hold for reflection of light. In order that the echo may return to the place from which the sound proceeds, the reflection must be direct, and not at an angle to the line of transmission, otherwise the echo may be heard by others, but not by the transmitter of the sound. This may be effected either by a reflecting surface at right angles to the line of transmission or by several reflecting surfaces, which end in bringing the sound back to the point of issue.
Sound travels about 1,125 feet in a second; consequently, an observer standing at half that distance from the reflecting object would hear the echo a second later than the sound. Such an echo would repeat as many words and syllables as could be heard in a second. As the distance decreases the echo repeats fewer syllables till it becomes monosyllabic.
The most practiced ear cannot distinguish in a second more than from nine to twelve successive sounds, so that a distance of not less than sixty feet is needed to enable a common ear to distinguish between the echo and the original sounds. At a near distance the echo only clouds the original sounds. This often interferes with the hearing in churches and other large buildings. Woods, rocks and mountains produce natural echoes in every variety, for which particular localities have become famous.
In Greek mythology, Echo was a nymph (one of the Oreads) who fell in love with Narcissus, and because he did not reciprocate her affection she pined away until nothing was left but her voice.
The Story of the Motion-Picture Projecting Machine[69]
Few businesses have had a more spectacular rise than the motion-picture industry. It may be true that there are other industries of recent growth that are more highly capitalized than the motion-picture business. I shall not make any comparisons nor look up statistics, but will present some facts about an enterprise that, scientifically, industrially and commercially, is one of the great wonders of the world.
It is fair to estimate that more than $375,000,000 is invested in this business in the United States. It looks like an exaggeration or as if the typesetter had slipped in several extra ciphers by mistake, does it not? Nevertheless, the estimate is said to be extremely conservative. In the first place, it concerns every branch of the business, of which there are five. Taken in their natural order there are: 1. The manufacture of motion-picture cameras. 2. The manufacture of films. 3. The taking of the pictures. 4. The manufacture of the projecting machines. 5. The exhibition of the pictures.
The projecting machine is the subject of this story. One sees very little about it in the newspapers and popular magazines, in spite of the fact that it is the keystone, so to speak, of the motion-picture industry. Of the entire business, in all its ramifications, this machine is the most important not only from a technical standpoint, but as regards both the pleasure and safety of the public. Here, again, a great deal of money is invested. Its manufacture involves costly and highly specialized machinery, the most intelligent of mechanics and the constant thought and endeavor of the men at the head of the business.
The advancement in the manufacture of motion-picture projecting machines from the start has been along two avenues—to secure better projection, a sharper, clearer and steadier picture, and to eliminate the danger of fire resultant from the ignition of combustible film. Experts have watched and studied the picture machine through all its stages of development. For seventeen years they have slowly improved the machine and brought it to its present high state of mechanical perfection. The development of the fireproof magazine, the automatic fire-shutter, the loop-setter, flame shields and the famous intermittent movement have all been vital factors in the elimination of fire and also in securing perfect projection. The oldest invention was patented by W. E. Lincoln on April 23, 1867. The contrivance was a mere toy, employing no light and being merely a little machine which, when revolved, gave figures, printed in different positions, the semblance of motion. The second oldest was of an “optical instrument” patented by O. B. Brown on August 10, 1869. This was really the first American motion-picture projection machine. There was a sort of disk or moving-shutter movement which, on revolving, gave projected objects the appearance of animation. Of course, there were no films in those days and the inventor had used translucent glass to obtain the results. Yet here was the germ of our native modern machine.
The Latest Motion-Picture Projecting Machine
A well-known moving-picture projecting machine manufacturer tells the following story: “A bet was made in 1871 by the late Senator Leland Stanford, of California, that a running horse at no time had all four feet off the ground. Edward Muybridge, an Englishman, by way of experiment, placed numerous cameras at regular intervals about the track, which, by electrical contact, were snapped by the horse in passing. It proved that the horse always had, when running, one foot on the ground. Although this was not the first record of motion pictures, it served to demonstrate their practicability.
“Development had dragged until the Muybridge experiment. In 1880 Muybridge produced, in San Francisco, the ‘Zoopraxiscope,’ which projected pictures (on glass positives) on a screen. Later Muybridge conferred with Edison regarding a combination of his machine with the phonograph, then in its infancy; about 1883 he went abroad and held frequent conferences with M. Marey of the Institute of France.
“Marey first utilized the continuous film, though it was George Eastman who brought it to its present state of high perfection. A great deal of the tremendous present popularity of motion pictures is due to the invention of the translucent film. The early kodak film became the great factor in the cinematograph manufacture.
The Construction of the Lamphouse Affords Easy Access
“In 1893 Lumiere produced the ‘Cinematograph,’ the first machine to project from a film. Edison in 1896 produced his ‘Vitascope.’ These machines became the models of the greatly improved article of today.
“The first real machine was brought to America in 1894. At least, that is as near as I can recollect the date. It was a Lumiere cinematograph and was exhibited at the Union Square Theater, New York City. The French manufacturing firm instructed J. B. Cole & Co. to furnish an operator. The Cole Company was interested in the sale of lanterns and slides and the foreign firm naturally turned to them for assistance.
“They furnished an operator, Edward Hadley. Although he had never seen a motion-picture machine, Hadley was a man who had been in their employ and was naturally familiar with lanterns and electricity. To the best of my belief, Hadley was the first motion-picture operator in America. He afterwards became the operator for Lyman H. Howe, the well-known pioneer traveling motion-picture exhibitor, and later became an exhibitor himself.
The New Arc Lamp
“The films then had one perforation on either side of each picture. That was the French method. The American method of four perforations on either side of each picture, formulated by Thomas A. Edison, was taken up later. The Edison perforation method became the standard in America and finally throughout the world. We find no more single-holed films.”
Here, for the benefit of the uninitiated, a little description of the film and the projecting head of a machine is necessary. A motion-picture film is a thin ribbon of transparent pyroxylin plastic or nitrocellulose, which is highly inflammable. The photographs on the film, one by three-fourths of an inch in size, leave a margin of five thirty-seconds of an inch on each side. In the margins are the perforations necessary to feed the film through the machine head. There are sixteen pictures to the foot.
The mechanism of the machine head moves the film over an aperture, so that the rays of light from the lamp will project an enlargement of the film picture upon the screen. The reels upon which the film is wound are mounted above and below—the upper is the feed reel and the lower is the take-up reel. Sprocket wheels control the action of the film. The top feed sprocket pulls the film from the upper feed reel, the middle intermittent sprocket (below the aperture) turns in a way to give each picture a certain time of stop over the projection aperture, and the bottom take-up sprocket assists in winding the film on the take-up reel.
Narrow Shutter Wings Afford Brighter Illumination on the Screen
“The early films were in very short lengths,” continued the manufacturer. “The average was from twenty to seventy-five feet. A hundred-foot film was considered extra long. They were mostly comic and not educational. The vast possibilities of the film had not yet dawned upon the pioneers. They aimed only to get a laugh with a crude comic picture.
“But those with more foresight realized that the film had come to stay. So the advancement began. Today the public is always looking toward something better. It has been educated up to an exceedingly high standard. The average spectator today can see a defect in an exhibited film as quickly as an expert.
“Machines in the early days were very crude, permitting only short films, which were an endless belt. They were threaded over spools contained in a box at the rear end of the lamphouse, passing over the lamphouse to the head of the machine; thence down through the head, past the projection aperture and back to the spools. This exposed the film at all times, which was extremely dangerous. About 1900, longer films came into use, which necessitated a change in handling. At the machine head, the film was piled on the floor. This being dangerous and destructive, a receptacle was devised and fastened to the frame below the reel, into which the film passed. This soon gave way to a reel known as the take-up reel, which received the film after it had passed from the upper reel through the head and before the aperture, where it was projected on the screen.
“These are a few steps in the march towards improvement. My first machine was called the ‘Peerlesscope.’ I kept continually improving it, and in 1902 changed the name to ‘Cameragraph;’ my latest machine, No. 6B, possesses every known device for safety—fire-shutters, which automatically cut off the film from the rays of the lamp while motionless; film-shields, which enclose and protect the film; fire-valves, which prevent entrance of flame into magazines; the loop-setter, which prevents breakage of the film while in motion, etc.”
Concerning projection, this manufacturer said: “Pictures cannot succeed without perfect projection, resulting in absolutely clear, flickerless pictures. The longer the period of rest of each picture on the screen, the better the detail and the clearer the picture. This I accomplished by means of an intermittent movement.
“You know that in projecting pictures the motion in the film is not continuous in front of the aperture of the machine head, each picture pausing long enough for proper projection on the screen. Through this intermittent movement I obtain a longer period of rest for each picture, which accomplishes perfect projection of pictures without flicker.
“A very annoying feature until recently has been the losing of the lower film loop, due to poor patching of the film, tearing of the perforations in the films, etc., causing the film to jump the lower sprocket, with the probable tearing and re-adjustment of the film. This I overcame with my loop-setter invention. To explain briefly—
“As the full movement at the upper and lower reel is continuous, while at the aperture it is intermittent, a loop is necessary as a feeder for the take-up or the lower sprocket. If this loop is lost, the film becomes taut, the machine stops and the film may break. The loop-setter instantly readjusts this loop automatically, keeping it always in force.”
The taking of pictures is, of course, one of the interesting phases of the business from a popular standpoint. Here we find not only large sums invested but the action, setting, plots—in fact, the entire order of pulsating life and convincing reality that give to motion pictures their remarkable hold upon the public. In vying with each other to make the most attractive films possible, the concerns in this end of the industry engage the most talented players, who are transported on long journeys so that the settings may be realistically satisfactory; while often the company includes not only two-footed actors, but horses, one or two clever dogs and sometimes a trained bear and other animals, besides all of which there is usually an array of “properties” that far exceeds in quantity and variety the list of such appurtenances carried by the average stock theatrical company or theater of the ordinary kind.
Then, too, there is the presentation of the pictures, where we find another vast outlay of money in land, buildings and equipment. And, remember, the matter of taking and presenting the pictures must not be considered only from the amusement standpoint. Motion pictures are being employed more and more every day for educational and industrial purposes.
The Story of Leather[70]
We all know that leather is the skins of animals, dressed and prepared for our use by tanning, or some other process, which preserves them from rotting and renders them pliable and tough.
The larger and heavier skins, such as those of buffaloes, bulls, oxen, horses and cows, are called “hides;” while those of the smaller animals, such as calves, sheep, pigs and goats, are called “skins.”
Scouring
The tanning of raw hides taken from animals is an ancient trade. The bark of trees made into a liquor has been used for centuries in treating practically all kinds of hides.
The oak, fir, hemlock and sumach are the most familiar of the many trees from which “tannin” is obtained for this purpose.
The cow hide is used practically altogether for sole leather and is bark tanned in the majority of cases. After the hide is taken from the animal it is either dry cured, or else salted green, and packed for shipment or storage.
The first process of preparing sole leather is to cut these hides in half or sides. The sides are then run through lime vats for the purpose of loosening the hair. They are then run through the unhairing machine, in which large rollers remove the hair.
From the unhairing machine the hides pass to a fleshing machine, which cuts away all the flesh or fat on the hide. They are then trimmed and scraped by hand, after which the real tanning process begins.
The old method of tanning leather was in large vats, which were filled alternately with tan bark and hides, then filled with water and allowed to soak for a period of eight to nine months before the tanning process was complete. The extract of bark in liquor form is used today by all large tanneries.
After the hides have been all prepared for tanning they are hung on rockers in the tanning vats, where they are kept in motion both day and night so that all parts of every hide are equally tanned. They are changed from time to time from weaker into stronger liquor until the tanning process is complete.
Tanning Vats
All sole leather is filled more or less to make it wear the better.
The drying process comes next. The hides are all hung in a dry loft, where artificial heat of different temperatures is used until they are thoroughly dry. The drying of the hide is as important as the tanning. Hides that are dried too quickly become brittle, so that great care must be taken in this drying process. Even the weather conditions play an important part.
Rollers
After the hides are thoroughly dried they are then oiled and ironed by large rollers having several hundred pounds pressure. This gives the grain side of the leather a finished appearance and also serves to press the leather together compactly.
Rubbing
Before this leather can be cut into sole leather it has to be again dried and properly edged to secure the best results.
Boarding Room
Bark-tanned leather that is used for upper stock in shoes is tanned practically the same way as the bark sole leather, except lighter hides are used and the finishing processes are of a nature to make it softer and smoother.
The above tannage is what is called vegetable tannage. There is also a tannage made from minerals that is called chrome. This is used mostly in tanning soft, glovey upper leather, which when finished makes a very tough yet soft and pliable leather for footwear.
Ninety to one hundred days are required to tan bark leathers, while the chrome tannage is very quick and on the average requires only about three weeks.
The brilliant smooth surface of patent, enameled, lacquered, varnished or japanned leather is due to the mode of finishing by stretching the tanned hides on wooden frames and applying successive coats of varnish, each coat being dried and rubbed smooth with pumice stone. There is also a process called “tawing,” which is employed chiefly in the preparation of the skins of sheep, lambs, goats and kids. In this process the skins are steeped in a bath of alum, salt and other substances, and they are also sometimes soaked in fish-oil. The more delicate leathers are treated in this manner, those especially which are used for wash-leathers, kid gloves, etc.
Measuring
In currying leather for shoes the leather is first soaked in water until it is thoroughly wet; then the flesh side is shaved to a proper surface with a knife of peculiar construction, rectangular in form with two handles and a double edge. The leather is then thrown into the water again, scoured upon a stone till the white substance called “bloom” is forced out, then rubbed with a greasy substance and hung up to dry. When thoroughly dry it is grained with a toothed instrument on the flesh side and bruised on the grain or hair side for the purpose of softening the leather. A further process of paring and graining makes it ready for waxing or coloring, in which oil and lampblack are used on the flesh side. It is then sized, dried and tallowed. In the process the leather is made smooth, lustrous, supple and waterproof.