CHAPTER XIV

PHOTOGRAPHY

Photography is one of the many triumphs of the human mind over time and space. Thousands of miles are between you and the wonderful Taj Mahal. You may never be able to go to it. But as the mountain would not go to Mohammed and Mohammed therefore went to the mountain, so photography brings the Taj Mahal to you. The chief struggle for civilization is with these two abstract antagonists--time and space. In this struggle the achievements of photography are such as to win it a place among the world's great inventions and discoveries.

Here, again, we borrow words from the Greeks. _Photography_ comes from the Greek noun _phos_ meaning "light" and the Greek verb _graphein_ signifying "to write," already referred to several times in this volume. Photography is therefore the science and the art of writing or reproducing objects by means of light. The science of photography depends upon the action of light on certain chemicals, usually compounds of silver. These chemicals are spread upon a delicately sensitized metallic plate, which is exposed to light. The action of light fixes the object desired upon this plate, from which copies of the picture are made on paper of suitable kind.

Like most of the great discoveries and inventions, photography is not old. It had its beginning in 1777, when the Swedish chemist Scheele began to inquire scientifically into the reason and effect of the darkening of silver chloride by the rays of the sun. The first picture ever made by the use of light on a sensitive surface was made in 1791 by Thomas Wedgewood, an Englishman. The principle of the photographer's camera was discovered in 1569 by Della Porta, of Naples. To Nicéphore Niepce, a Frenchman, belongs the honor of producing the first camera picture. This was in 1827 after thirteen years of experimenting. He called his process "heliography," _helios_ being the Greek word for _sun_. His process consisted of coating a piece of plated silver or glass with asphaltum or bitumen, and exposing the plate in the camera for a time varying in length from four to six hours. The light acted on the asphaltum in such a way as to leave the image on the plate.

The predecessor of the modern photograph was the daguerreotype. It was named for its inventor, Louis Daguerre, a French scene-painter, who was born in 1789. In 1829 he formed a partnership with Niepce, and together they labored to advance the art of photography. The discovery of the daguerreotyping process was announced in January, 1839. The process of Daguerre consisted in "exposing a metal plate covered with iodide of silver for a suitable time in a photographic camera, the plate being afterwards transferred to a dark room, and exposed to the vapor of mercury, which develops the latent image, it being afterwards fixed. Although this process has become almost obsolete, it was really the first which was of any practical value, and experts all agree that no other known process reproduces some subjects--for example, the human face--with such fidelity and beauty."

A little while before the daguerreotyping process was announced, Fox Talbot, a British investigator, discovered a method of making pictures by means of the action of light on chemically prepared paper instead of metal, as in the case of Daguerre. Talbot originated the terms _negative_ and _positive_ which are still used in photography. Daguerre in France and Talbot in Great Britain had independently achieved success in producing pictures, but neither had discovered a way to make photographs permanent. In the course of time the pictures faded. In 1839 Sir John Herschel of England found a chemical process for making photographs permanent, by removing the cause for their fading. The first sunlight photograph of a human face was that of Miss Dorothy Catherine Draper, made by her brother, Prof. John William Draper, of the University of the City of New York, early in 1840.

Various chemical discoveries for improving photographs have been made by different persons from time to time, until the art of photography has now reached a high state of development. An important improvement is in the lessening of the time of exposure to light necessary for producing a photograph. Formerly hours were required, but under improved conditions only the shortest instant of time is requisite.

In 1906 a photographic paper for producing prints in color from an ordinary negative was placed on the market. This paper is coated with three layers of pigmented gelatin, colored respectively red, yellow, and blue. After being exposed to the daylight in the usual way, the paper is placed in hot water, where the image is developed. The grays and blacks of the negative are translated into the colors they represent in the object.

The brothers Lumière of Paris have found a method of producing a photograph on a sensitive plate which, viewed as a transparency, shows the object in its original colors. No prints can be taken from this plate, and the picture cannot be viewed by reflected light, but the colors are true and brilliant.

The cinematograph is an instrument by which about fifteen photographs per second can be received on a film, each representing the photographed group at a different instant from the others. The advantages of this mode of photographing and of throwing pictures on a screen over the older methods are obvious. By controlling the rate at which the pictures are represented on the screen, movements too rapid to be analyzed by the eye may be made slow enough to permit observation; and, similarly, movements too slow for comprehension or rapid observation may often be quickened. The busy life of a city street, the progress of races or other competitions, many scenes in nature, and even the growth of a plant from seed to maturity, may be shown by means of a "moving picture."

Photography is a noble servant of mind and soul. It brings to us likenesses of eminent persons and objects of nature and art which perhaps we should never be able to see otherwise. It has been used in measuring the velocity of bullets and in showing the true positions of animals in motion. Photography has created the "new astronomy." Immediately after its discovery, photography was applied to the science of the stars, and it has been ever since of incalculable service in this field of inquiry. Photographs of the moon were made as early as 1840, and much that is known to-day of the sun has been revealed by photography. So sensitive is the modern photographic plate to the influence of light, that photography has discovered and located stars which are invisible through a strong telescope. Astronomers are now engaged in making a photographic chart of the sky.