Light.

Selected writings of A. Jackson Howe.

This is another section from the article on "Matter and Energy." Such papers as this were frequently published in the Eclectic Medical Journal, for Dr. Howe contended that physicians should read widely outside of the direct subjects of medicine and surgery. The pages of this journal are rich repositories of many such brief dissertations on natural phenomena that Dr. Howe insisted should be a part of the general education of the well-rounded physician. It is to be regretted that fewer articles on such subjects now appear in medical periodicals.—Ed. Gleaner.

LIGHT.—Heat is the manifestation of an energy, and so is light. The glow worm and the fire fly flash phosphorescence on summer nights, and the "will o' the wisp," or swamp gas, is a torch lighted through the agency of decompositions. The farthing dip feebly illumines the humble cottage, and electric incandescence makes brilliant the halls of palaces. When brakes of a swiftly moving train are applied the friction evolves heat enough to kindle a flame, and a spark is elicited by a stroke of flint and steel. Light is emitted in rays from a center of illumination, as the flame of a burning lamp, a blazing meteor, from stars and from the sun. The "fixed stars," so called, issue luminous rays as the sun does, but they are so far away that we see only a stellar twinkle. Light from the moon is wholly reflected, solar rays glancing from the face of the lunar orb to the earth. Sunbeams differ somewhat from other luminous rays. A pencil of sunlight thrown upon a spectrum or glass prism will exhibit plainly the primitive colors, and rays from the electric arc display such hues, but not so prominently. Plants do not thrive as well under artificial heat and light as they do under the sun s energies. Solar rays decompose carbonic acid in the leaves of plants through the agency of chlorophyll, the carbon forming woody fiber, while the oxygen disengaged passes into air. All the colored rays of the sun will not decompose the carbonic acid of plants, but the actinic or chemically active blue and violet rays. Plants may develop in substance without the aid of sunbeams, but the stalks and leaves are colorless, and the acme of maturity can hardly be attained.

Light has been denominated an energy, and not an ethereal substance. It may be transformed into heat and electrical units— it may assume two or three kinds of energy. The sun is the great source of light in its own system, but looked at from Sirius its twinkle becomes a star of the fourth or fifth magnitude. The vivifying powers of solar energy are all important to our planet. Without the influence of light and heat the earth would have no seasons, no plants, no animals, no rains, no atmosphere, no condition contributing to the support of life. In shaded places poisonous fungi may vegetate, and in the deeper parts of the sea where heat does not reach, nor solar rays penetrate, there may he encountered organic forms, both floral and faunal, hut their support is borrowed from material that has been under the sun's influence. Near the poles the water swarms with marine life, but the water is rich in protoplasm that has been developed under the energies of a tropical sun. The energizing influences of solar rays are stored in tree?, and eventually laid away in coal banks, hence their character should be considered in the economics of our planet.—HOWE, Matter and Energy.

The Biographies of King, Howe, and Scudder, 1912, was written by Harvey Wickes Felter, M. D.