As his first subject he selected an overhead trestle bridge, which carried the streetcars across the railroad yards at the Monument Street crossing. This should give a good idea of how an overhead bridge appears to a fish in a quiet stream below it. Placing the sinister-looking black box on the ground, he was annoyed to find himself surrounded by an interested group of colored children, who had followed him to see what it was all about. As they would of course ruin the picture, he told them to clear out, an order which was greeted by giggles. An exposure of a minute would be required, and Wood suddenly had an inspiration. Lighting a match, he held it against the side of the box, shouting, “Beat it, or you’ll be blown sky high”, and raising the lid of the box, he hurried away. The crowd scattered in all directions, and at the end of a minute he returned, closed the lid, and strolled back to his laboratory.
While the scientific significance of the fish-eye camera was given to the world in the British Philosophical Magazine and other technical journals, our Literary Digest and the Illustrated London News took it up from the point of view of the fish — particularly the fish in aquariums who seem generally to stare just as much at us as we do at them — and probably think we’re just as queer.
In 1908, the Woods bought the old Miller farmstead, with its pre-Revolutionary house and huge barn and its remaining five acres of land, near the seashore in East Hampton, Long Island, far out toward Montauk Point. There are deeds of conveyance dating back to 1771, and the hand-hewn beam structure of the buildings indicates that they too may date back that far.
Wood transformed the immense barn and its adjacent cowshed at East Hampton into a summer laboratory. Both here and at Johns Hopkins, he was absorbedly at work throughout these years — despite diversions and digressions — with new experiments, discoveries, and inventions. He later invented and installed beneath the cowshed the mercury telescope which made a world-wide sensation; he also built the largest spectroscope (or spectroscopic camera) in the world, and cleaned it of spiderwebs with the unwilling co-operation of the family cat[8]. He took aerial photographs by sending a camera up on a kite and releasing the shutter with ordinary firecracker punk. He made the further steps which were to mark a high light in his career by resuming and improving the photography of the moon with invisible ultraviolet light, which he had begun back in 1903.
He also took terrestrial time out, as it were, to debunk the complicated theory evolved by purely academic physicists to account for the high temperatures obtained in conservatories and greenhouses, which had crept into nearly all textbooks that mentioned the matter at all. It is well known that glass is quite opaque to the greater part of the sun’s spectrum beyond the red, that is, the region of longer wave lengths. The old theory considered that the visible light and shorter heat waves passed through the glass and heated the ground. The ground, thus heated, was supposed to give out radiation of such long wave length that it could not pass through the glass and was therefore trapped.
Wood’s theory was merely this: the glass house lets in the heat rays, which warm the ground, which in turn warms the air. This warm air is shut in by the house, instead of rising to the clouds as it does in the open. If you leave the doors of a greenhouse open, what becomes of the old theory?
He proved his case by the following very simple experiment. Constructing two enclosures of black cardboard, he covered one with a glass plate and the other with a plate of transparent rock salt. The bulb of a thermometer was inserted in each enclosure, and the apparatus exposed to sunlight. The temperature rose to 130° Fahrenheit, practically the same in each bulb. The rock salt is transparent to practically all of the heat radiations concerned, and on the old theory the enclosure covered by this material should not show the greenhouse effect, that is, there would be no trapping of radiation and the temperature of the enclosure would be much less.
In December, 1908, Wood was called upon to give a public lecture dealing largely with color and its application to paintings (the word “color” here refers to light rather than to pigments). Partly as a demonstration to enliven this lecture and partly because he thought it might have some use in stage lighting, he had worked out an optical method for the intensification of the color of paintings. Wood had occupied himself with the painting of landscapes in oil for some time as a diversion and had frequently noticed that a spot of sunlight, coming through chinks in the foliage and falling upon a green meadow in the picture, had produced a pleasing effect.
It occurred to him that if this enhancement of the illumination could be applied to all of the high lights in the picture in proper proportion, there would probably be a startling increase in the brilliancy of the picture. The whitest paint is only about sixty times as bright as the darkest paint ever employed by artists, whereas the ratio of intensity of sunlight on a white building to the deep shadow of a doorway may be as much as a thousand to one.
He found a way of intensifying the light contrasts in paintings by photographing the original painting, preparing a lantern slide from the negative, and projecting it with a lantern placed at such a distance as to secure exact registration of the image on the original. In this way, a powerful illumination was thrown on the high lights and a feeble light on the shadows, with all the intermediate gradations correctly controlled. The effect in a dark room is quite startling — a landscape fairly glows with sunlight. After viewing it for a few minutes, if the lights in the room are turned up and the lantern turned off, the picture looks as if it had not been dusted for years. The audience was amused when a large portrait of a prominent trustee was illuminated in this way, and Wood found that by joggling the projecting lantern the pupils of the portrait’s eyes glanced rapidly back and forth from right to left in a most lifelike manner.
Wood saw a possible practical use of this discovery in connection with stage effects, in which the painted backdrop could be illuminated by a lantern in the gallery which projected upon it a photograph made in a similar manner. This, he thought, should be particularly effective in sets which were supposed to be drenched in sunlight.
Wood’s most important work, however, continued to center around the optical investigation of sodium vapor. Examining the absorption spectrum of sodium vapor in the ultraviolet, he succeeded in increasing the number of lines of the principal spectral series from the eight previously known to fifty. It was, and still is, the longest spectral series known. This discovery was later cited by Niels Bohr as a beautiful proof of his new theory of atomic radiation, for which he received the Nobel prize. Another experiment of Wood’s at the same time that was also important in the new theories of radiation was his demonstration that the fluorescent light emitted by sodium vapor (and potassium and iodine vapor as well) was polarized — that is, a large percentage of the light vibrated in a single plane. At the same time, Wood was working with one of his students, H. W. Springsteen, on magnetic effects on polarized light. Corbino, an Italian physicist, some years previously had noted that by placing a sodium flame between the poles of an electric magnet and passing a beam of polarized white light through it, the plane of polarization of some of the yellow light was rotated several degrees. Wood and Springsteen, working with metallic sodium heated in a glass tube instead of a sodium flame, obtained rotations as great as 14° in the yellow region, and discovered marked traces of rotation in other regions of the spectrum. Wood was to continue this work for a number of years, with more powerful magnets and improved technique, obtaining rotations as great as 1,440° or four complete revolutions, results of great value to the theoretical physicists.