AFTER God had created the heaven and the earth, "the earth was waste and void; and darkness was upon the face of the deep." So the Creation story in our Bible runs. Then "the spirit of God moved upon the face of the waters. And God said, Let there be light: and there was light."

That was the great beginning. When there was light, all else could follow in due course. Plants could grow and flourish. Men and the animals could dwell on an earth where there was light.

The first light which man created for himself came from the fire. In firelight man began his age-long conquest of darkness. In the homes of the cave dwellers there are niches in the rock where fires were built above the level of the floor to serve as light-givers during the long, dark hours.

Some day another means of lighting was discovered. Perhaps a cave man returned late from the hunt, dressed his meat hastily, and handed it to his woman to cook over the fire. But by the time the meat was half cooked darkness had fallen. The smoky open fire gave only a feeble light. While the man and his woman and children were groping about in the shadows, a pool of hot fat which had dripped from the carcass of the animal as it cooked suddenly caught fire and blazed up. The whole cave was illuminated. By the light of the burning oil in the hollow of the stone floor the members of the family could see one another and partake in comfort of their food. So long as the hot oil burned, there was light.

After that the cave woman probably kept bear’s grease or sheep’s fat and heated and lighted it in a hollow shell. Some day she, or some descendant of hers, thrust a piece of wood into the burning liquid. It soaked up the fat and burned longer, with less smoke, and more evenly than a separate piece of wood or than the burning oil. That was the first oil lamp with a wick.

Lamps did not change much until modern times. The oil lamps of the days when the Pyramids were built were not unlike those of the cave dwellers or those of Cæsar and his Roman cohorts planning hundreds of years later to conquer the world. The hollow shell became a metal or earthenware bowl; the wick was of the marsh plant called "rush," or of linen threads from the flax plant, or of slow-burning pith; there was a groove or stem for the wick. But the lamps of Egypt, of Greece, and of Rome, as we see them in museums, are all of the open, oil style with their smoky flickering light.

The Phœnicians discovered for themselves or learned somewhere in their trading trips the secret of candle making. They knew how to dip a slowburning wick in a mass of hot beeswax and to keep on dipping and cooling, dipping and cooling until they had a rude candle. Their candles date from 400 or 500 B.C. Candles made from the fat of sheep and oxen came later.

But candles and oil lamps were all the means of lighting which the world possessed down to the time of the founding of the American Republic and the beginning or even the middle of the nineteenth century. The lamps were made very beautiful; the chandeliers to hold candles were of dazzling crystal, which gave back rainbow colors from their flickering light. All kinds of shades and reflectors were introduced. There were short metal lamp chimneys. Whale oil was substituted in lamps in our own country for vegetable oils and animal fats. But still, in spite of these minor changes, the flame was produced in the same way and the light was consequently very poor. At a reception given to Washington in Philadelphia the lighting was considered uncommonly brilliant since two thousands candles were burning at the same time.

The conquest of darkness in our homes and on our streets has come in the train of other great scientific discoveries. The finding of natural gas in the ground and the making of gas from coal started one line of inventions for illumination. Electricity applied to lighting has turned darkness into day in our homes and made our city streets "White Ways" by night. By an electric current in a vacuum tube man has been able to separate partially light and heat and to get away from the age-long union between the fire and the light. The successes of modern lighting came in the field of invention. By clever devices man has learned to create small lights for himself which serve him when the great light of the world, the sun, withdraws its brilliance.

The wonders of light are only begun in the story of the conquest of darkness by the creation of artificial lights. Through another set of devices man has learned to make the light of the sun his servant in revealing secrets of the world hidden from his unaided vision. By the telescope, the microscope, the photograph, and the X-ray, he has been aided by light in additional conquests of time and space. Light, with its ally, transparent glass, has opened to him new worlds.

Men used spectacles three centuries before the telescope was invented. They found that if they looked through a piece of glass with a slightly curved surface, the objects appeared larger than when looked at with the naked eye or through plain, flat-surfaced window glass which did not bulge out on one side.

Galileo, the brilliant Italian scientist who discovered as a youth the law of the pendulum, knew about magnifying glasses and lenses and spectacles; but he had apparently never thought of using them for viewing such distant objects as the moon and stars, although his main interest was for a time in studying the heavens. The way the idea came to him is interesting.

A Dutch maker of lenses and spectacles, by the name of Hans Lippershey, had in his shop a queer instrument, put together, as the story goes, by one of his apprentices, with two spectacle glasses so set in a tube that a person looking through the tube would see the weathercock on a neighboring church spire appearing larger than when seen with the naked eye, but upside down. In that shop this toy, which was really the first telescope, might have remained unnoticed save as a curiosity. But Marquis Spinola, an Italian gentleman, happened into the shop, was interested in it, and bought it. He took it to Prince Maurice of Nassau, who thought of using it in military work when he wanted to spy on the enemy’s territory without risking too close an approach.

Now the story comes to Galileo, where it is told in his own words in a letter written by him to his brother-in-law.

You must know, then [he writes], that two months ago there was a report spread here that in Flanders someone had presented to Count Maurice of Nassau a glass manufactured in such a way as to make distant objects appear very near, so that a man at a distance of two miles could be clearly seen. This seemed to me so marvelous that I began to think about it. As it appeared to me to have a foundation in the Theory of Perspective, I set about contriving how to make it, and at length I found out, and have succeeded so well that the one I have made is far superior to the Dutch telescope. It was reported in Venice that I had made one, and a week since I was commanded to show it to his Serenity [the Princel and to all the members of the Senate, to their infinite amazement. Many noblemen and senators, though of advanced age, mounted to the top of the highest bell-towers in Venice to spy out ships at sea making sail for the mouth of the harbor, and have seen them clearly, though without my telescope they would have been invisible for more than two hours. For it makes a thing fifty miles off as near and clear as if it were only five.

Galileo’s house was the chief attraction in Venice in the days of this new wonder. Morning, noon, and afternoon distinguished visitors, ladies of the court, and scholars came to peer through his tube.

It was a queer little telescope he had made. The day he heard of the Dutch instrument he began to ponder on this new idea and stayed up all that night working on schemes. What he finally did was to take an old small organ pipe, jam a spectacle glass that was convex (that is, curving outward) into one end, another that was concave (curving inward) into the other end. The result magnified three times and did not turn the image upside down as the Dutch instrument had.

No discovery ever achieved more instant popularity. Galileo’s home was nearly mobbed by the crowds in Venice. The Italian Senate suggested that they would like a telescope, and when he presented them with one promptly doubled his salary at the University of Padua and made his engagement there a life position.

Galileo was the first to turn the telescope on the heavens. Working with infinite patience and skill he succeeded in making an instrument that would magnify thirty times. The day when he turned it on the heavens marked the beginning of a new age in astronomy.

He first looked at the moon and was amazed to find there a rough surface with the appearance of mountains and valleys instead of the smooth surface which everyone had previously imagined to be there. He was greatly surprised to find so many stars, ten times as many as he had ever seen with his own unaided vision. And to find that the Milky Way which had so puzzled the ancients was made up of stars—that was so incredible that no one believed him when he asserted it!

But Galileo’s great moment in the use of his telescope was still to come. That was when he turned his tube on the great planet Jupiter. Galileo lived in the days when the old theory of Aristotle and Ptolemy was still believed, that the earth was the center of the universe and that all the planets and stars, as well as the sun, moved about the earth for their center. To be sure, Copernicus had propounded within sixty years of Galileo’s time the true idea that the sun, not the earth, was the center of our system, and that the earth and the planets revolved around it. But Galileo and some of the new astronomers who had adopted this revolutionary idea were bitterly opposed by the members of the old school, who held to the beliefs of a thousand years and would have none of these new and upsetting ideas. Galileo had gotten into trouble with these men before. His telescope seemed to restore him to popularity, but its discoveries were to make them more trouble than anything he had previously said.

On January 7, 1610, one year after he had made his first telescope, examining the planet Jupiter through his instrument he saw three little stars near it. He noted them down, taking their exact positions. The next night he looked again, and Jupiter was on the other side of the three little stars. If the sky with the stars set in their places was moving around the earth, as the old astronomers argued, this was not impossible, except for the astonishing fact that according to the plan the three little stars were on the wrong side of Jupiter. That Galileo could not understand. He waited in a fever of impatience for the next night, but it was cloudy. On January 10 he could see again, and this time there were only two stars and they were on the other side. On the 11th there were two again; on the 12th, three as at first; and on the 13th, four. After that no more appeared.

What Galileo had seen was the four moons of Jupiter, moving around it, as our moon moves around the earth. This he at once realized. It was a wonderful sight to him, for he had been saying for some time that our moon moved about the earth. But people would not believe it, for they were strong for the old theory. Now he could say, "Come, and I will show you with my telescope how another one of the planets, Jupiter, has four moons which swing around it as our moon swings around our earth." He did say so. News of the discovery spread far and wide. But how hard it was for people to believe it! Some said that Galileo had bewitched the telescope. Others refused to look through it. One man said that if he saw the moons of Jupiter himself, he would not believe in them, as their existence was contrary to the principles of common sense!

But Kepler, a fellow astronomer, who was one of the great pioneers in the new science, took the discovery very differently. He wrote to Galileo:

I was sitting idle at home thinking of you, most excellent Galileo, and of your letters, when the news was brought to me of the discovery of four planets by the help of the double eyeglass. Wachenfels stopped his carriage at my door to tell me, when such a fit of wonder seized me at a report which seemed so very absurd (and I was thrown into such agitation at seeing an old dispute between us decided in this way) that between his joy . . . and the laughter of us both, we were hardly capable, he of speaking, or I of listening. But I am so far from disbelieving the existence of the four circumjovial planets that I long for a telescope to anticipate you in discovering two round Mars, . . . six or eight round Saturn, and one each round Mercury and Venus.

With such a spirit of open-mindedness did a really great scientist welcome a discovery which disproved some of his own hard-won ideas about the planets.

Galileo invented a few years later the microscope, which was to reveal the wonders hidden from our vision by their minuteness as the wonders of the heavens are beyond our sight because of their vastness. In the very last years of his long life he became blind. He writes then to a friend:

Alas, . . . , this earth, this universe, which I by my marvelous discoveries and dear demonstrations have enlarged a hundred thousand times beyond the belief of the wise men of bygone days, henceforward is for me shrunk into such small space as is filled by my own bodily sensations.

Truly he had enlarged the world beyond all the thinking of earlier ages. By means of the telescopes and microscopes of to-day man has enlarged his vision one hundred thousand times beyond the wildest dreams of Galileo himself. All honor to the great pioneer and inventor who in 1610 looked at the heavens through a tiny, home-made telescope!

The Telescope at the Mt. Wilson Observatory, California Man's vision is enlarged one hundred thousand times when he peers through this gigantic telescope.

A photograph is a "light picture" or a "light writing." The name comes from the two Greek words, photo meaning "light" and graphein, the familiar verb "to write." We find the same word in the "telegraph," which means a "far-off writing" or a "writing across a distance." Photography is well-named since light does write the picture on the sensitive film in the camera.

Men knew that light could "write" or "paint" pictures long before they knew how to make it take just the pictures man wanted taken and print them on a film which would hold the writing.

A mirage in the desert is a light picture. You have read how travelers will journey many miles toward a green oasis in the desert which seems always to be just beyond them, only to find that it is an empty reflection of a far more distant scene which has been caught and held by light. A reflection in a mirror is one kind of a light picture though not the kind used in photography.

The Greeks who gave us so many of the names which we use in this story made and named the first cameras. A camera is a "room," a camera obscura is a dark room. Perhaps you have seen for yourself the kind of light pictures which can be made by a dark room. If in a room made wholly dark a tiny hole is punched in the curtain covering the window, the sunlight will stream in and "write" on the wall opposite the window a picture of the house across the street, though that house will appear to be standing on its head.

The Greeks probably made dark-room pictures; but the Secret was lost for a great many years and discovered again in the Middle Ages. Of all the persons who made discoveries no one ever had a better time with his invention than the Italian philosopher who thought he found this secret out for the first time, Battista della Porta, who lived about a hundred years before Columbus. He set up a dark room in his home in Naples to which crowds flocked to see these "pictures painted by light, glowing with color and marvelously accurate." The pictures appeared on a white wall opposite the hole where the light came in, and showed up quite sharply and distinctly, though they were still upside down. So Porta had a wonderful time showing his pictures to the crowds which visited him, and then he wrote a book on "Natural Magic" in which he gave full directions for getting these effects. This book was sold all over Europe, and gave to the camera obscura an immense popularity. A glass ball set in the hole served as a lens and made the pictures clearer; and a dark box with a hole in it took the place of the dark room. Artists could carry these "cameras" with them and study the scenes they wished to draw or paint through them, often doing the actual drawing with their aid.

We smile at any one’s going into such raptures as the old Italian did over seeing an outdoor scene reflected through a pinhole on a white wall. But Porta and the camera makers and the lens makers were getting ready the box and the lens which were to make our modern camera. They had the pictures. What was needed was the right kind of surface on which to catch and hold the images which they were seeing through the lens or throwing on a white wall.

It was two hundred years before the chemists had made ready the materials with which that could be done.

Louis Daguerre was a scene painter for Paris theaters. He often used the camera obscura to help him in his painting, and about the year 1824 became interested in the idea of trying to "fix" the image which the camera gave. We can hardly follow him or the other inventors of that time through the long maze of experiments with this chemical and that, or with this substance or that on which to "catch" the picture. One scientist, who was working with microscopes in a study of insects, used leather for his printing surface and succeeded in getting a faint image of a flea, 150 times enlarged, on his wife’s kid gloves. But naturally his wife did not encourage his further experiments. He finally got results on paper treated with tannin. Another worked with flat paving stones for printing plates, and finally got an image which he held on tin. The story of every one of the pioneers working in this field is fascinating; the credit for discoveries in the line of photography belongs to several French and English inventors. But the thrilling moment came when Daguerre in his laboratory fixed the first imperfect image and exclaimed: "I have seized the light! I have arrested his flight! The sun himself in future shall draw my pictures!"

Daguerre had been experimenting for many years. He had been in partnership with Niepce, the man who began with paving stones as plates for his images and who finally caught and held an impression on a plate of tin treated with certain chemicals. But Niepce had died after experimenting for fourteen years and the process on which they had both worked was far from successful.

One day Daguerre laid a silver spoon on a metal which had been treated with iodine. When he picked up the spoon, he found that its image was printed on the metal. That showed him he was doing well to use iodine. He now added the idea of a silver plate treated with iodine on which to catch the picture. He put his plate into his camera, but the image was almost too faint to see. He was bitterly disappointed.

Because the plate was of silver and therefore too valuable to destroy, he laid it away in a cupboard. The next morning he went bravely at the work again, in spite of his disappointment. But when he opened the cupboard, what was his surprise to find a fairly clear picture on the silver plate instead of the very faint and shadowy one which he had left there the day before? Some chemical in his cupboard must have done in the night the work of bringing out the faint image of the day before. But what chemical?

Then began a series of days and nights full of excitement for Daguerre. Each day he took out one chemical from the cupboard. If the plate should show up the next morning with a clear image without that chemical in the cabinet, plainly that chemical was not the magical one which was so mysteriously and silently doing the desired work for him. Each day he took out his chemical, and still the results were the same until finally there was only one bottle left. That must be the one. Still to make sure he left a fresh plate in the empty cabinet. The next morning he went as usual, and behold! the plate was developed as usual in spite of the fact that every bottle was gone. Then he was puzzled indeed! But a careful search of the cupboard revealed that a few drops of mercury (the silvery liquid which we see in our thermometers) had spilled on the bottom shelf. Their vapor had been the wonder worker which was responsible for bringing out the shadowy and indistinct print on the silver plate.

With that secret revealed well might Daguerre say, "I have seized the light! . . . The sun himself . . . shall draw my pictures!"

On August 10, 1839, the French Academy of Fine Arts met with the French Academy of Sciences to honor Louis Daguerre, the scene painter of Paris. Throngs of artists and students waited outside in the streets while Arago, the most celebrated scientific man in France at that time, announced to the distinguished company of scholars that Daguerre had successfully produced a permanent photography. Light had written on silver, and that writing had been preserved.

Daguerreotypes, as these first photographs were called in honor of their inventor, were taken in America within a week after the public announcement of the method was brought to this country by a copy of the London Literary Gazette. Samuel B. F. Morse, the inventor of the telegraph, photographed his daughter; a New York physician bought the necessary supplies and succeeded in getting a good "sunprint" of a church and also a portrait. Daguerreotypes became common; but how trying it was to sit for one’s picture! One had to sit motionless for twenty minutes in the most brilliant sunlight while the image was slowly etched on the metal plate. A photographer could open his camera, walk to his place in the sitter’s chair, remain there for the necessary time, walk back and close the camera, thus taking his own photograph with no effect shown on the plate of his absence from the seat at the moments of the beginning and ending of the operation.

Nevertheless, the instantaneous photograph of to-day, the color photograph, the motion picture film, the photographs sent by wire or by radio, and all the rest of the modern wonders, trace their ancestry back to the simple dark box with its glass ball in which men learned to catch and then to fix on a chemically treated surface the "light picture."

The Camera The camera plate receives the image upside down because of the bending of the light rays by the lens. Forms of Lenses 1. Plano-convex 4. Plano-concave 2. Biconvex 5. Biconcave 3. Concavo-convex 6. Meniscus 7. Light rays bend and meet in passing through a biconvex lens.

In January, 1896, cable messages began to be printed in American periodicals that a Professor Roentgen at Wurzburg University in Germany had discovered a new kind of light that drove through solids as if they were not there. It seemed a wild story and the scientific papers were very cautious in their reports. One of the best science journals prints these cables with this comment: "It is yet too soon to indulge in the wild possibilities that have been suggested for this process. When the details reach us, the process will probably prove to be of scientific rather than of practcal interest." This comment, by the way, was on the same page with two equally cautious articles on the "horseless carriage."

Yet so fast does the world move that to us it is a commonplace of everyday life that if the baby swallows a safety pin or a boy breaks his arm or a dentist wants to find out something about the root of a tooth, the patient is immediately sent to an X-ray photographer who will take a picture that will look through all the outer coverings of skin and flesh and show how things are inside the body. The "process" has certainly proved to be "of practical interest" to the most humble and unscientific person. Let us see how this discovery came about.

Light comes to us in waves, striking against the surfaces which stop it as the waves of the ocean beat against the shore. The eye is a camera which receives and focuses those waves and carries the report of them to the nerves connected with our brains. But just as a radio set is tuned for certain wave lengths and does not catch others, so the eye is "tuned" to a certain group of light waves and does not "see" with the other waves which may strike against it. All this knowledge of a great keyboard of waves coming through the ether of space, which explains electricity and radio and X-rays and many other curious and interesting things, was hardly known at all in 1895 when Professor Wilhelm Conrad Roentgen made his discovery in his laboratory at Wurzburg.

Scientists had begun in the latter part of the nineteenth century to find out about some of these things. In particular they were experimenting with a tube from which the air had been drawn out. When they drove a current of electricity through such a tube queer lights which they did not understand were given out. Roentgen was working with one of those vacuum tubes when he discovered X-rays.

He had covered the tube with a heavy shield of black cardboard. So he knew no ordinary light would come from it. Yet he noticed that on a piece of sensitive, chemically treated paper lying on the bench where he was working a peculiar black line had appeared. Such a line could only come, according to anything he knew, from exposing the paper to a strong light. Yet where was the light coming from? He had been passing an electric current through the tube. The effect must come from it, in spite of the heavy covering of black cardboard.

That was on the 8th of November, 1895. He began at once to try out these new light rays which he was getting. He could not see them, but they were evidently there, for they acted on sensitive screens such as the paper where he had noticed the first mark. He put wood and cloth between the tube and the screen. The rays went right through. He tried metals with the same result. Then he put his hand between the tube and the screen, and the outline of the bones showed through the flesh. For the first time in history a man could see his bones through the flesh that covered them. Next he tried to get a photograph of his hand as the bones were shown by these new rays, and found he could do that.

The discovery was announced at the December meeting of a scientific society in the little town of Wurzburg. On January 4, 1896, Doctor Roentgen read a paper describing it to the Berlin Physical Society. Within three or four weeks the news of it had gone all over the world.

"X-rays," Professor Roentgen called these new rays of light, so unlike anything ever seen before, for "X" stands for "unknown." Although they are now far better understood than they were in 1895, still it can never cease to be a wonder and a mystery that by their use a man can actually take photographs of objects which he cannot see with his own eyes.