Page:Popular Science Monthly Volume 1.djvu/786

766 ultimately the fundamental note or a single vibration was exhibited. Very high harmonies were shown by means of a very flexible string with a high velocity dividing the revolving tape into very numerous equal segments of vibration, or, as the professor preferred to call them, harmonics.

Petroleum In Santo Domingo.—In a note to the Mechanics' Magazine, Mr. William M. Gabb describes a petroleum-spring situated three miles north of the town of Azua, in Santo Domingo. It is near a stream, the name of which signifies "stinking water." The spring makes its appearance as a stagnant, torpid pool, exuding slowly through a heavy gravel-deposit. A very small area in the vicinity is covered with deposits of pitch, and, for half a mile down the dry bed of a rain-water stream, the gravel and sand are more or less cemented by an impure pitch, sometimes plastic, oftener hardened to asphaltum. The water is colored a dirty brown by the presence of the oil. Jets of gas bubble up at different points near the spring. The gas is not inflammable, and has more of a fetid than kerosene odor. In appearance and mode of occurrence the spring strikingly resembles those of Trinidad and California. It is the only spot on the island where bituminous products are found.

Photographing the Eye and Ear.—Dr. Vogel writes to the Philadelphia Photographer as follows: "That the interior of the human eye has been photographed is well known. The experiment is a somewhat cruel one for a living subject; still there are victims who stand it. I know, for instance, a very handsome young lady, whose brother is a physician, who patiently takes extract of belladonna until the pupil has become sufficiently enlarged; the interior of the eye is then illuminated with magnesium-light, and photographed. In a similar manner has the ear been photographed, that is to say, the tympanum only. A tube is inserted, in which is a mirror inclined at a certain angle. The mirror throws light into the interior of the ear. The mirror is also provided with a central hole through which the illuminated tympanum can be inspected. A system of lenses projects an image on the sensitive plate, and the picture is made in the ordinary manner."

Chemical Influence of Light.—In a recent lecture on the chemical action of light, Prof. Roscoe gives some interesting facts concerning the chemical effects of sunlight at different times of the day, and in different atmospheres. The number of chemically-active rays vary throughout the day. Their maximum is always highest at noon. The curve of the heating rays reaches its highest point after noon, but this is not the case with the chemically-active rays. The chemical intensity appears to depend solely on the height of the sun in the heavens, and at the same distance from noon; on either side it appears to be equal. The chemical power of sunlight also varies with the place. Prof. Roscoe gives the results of measurements at Kew, Lisbon, and Para. At Kew the intensity was 94.5, at Lisbon 110, and at Para 313. An opalescent atmosphere appears to cause the absorption of a large number of the chemically-active rays. Hence the important advantage, in point of vegetation, which those countries have where the atmosphere is clear.

The Leaf a Vicarious Organ.—Some interesting experiments have lately been conducted by M. Calliet, to determine the precise action of plant-leaves in the absorption of water in the liquid form. They have led him to the conclusion that leaves do not absorb water while the roots are supplied. But when the ground is too dry for the roots to obtain it, if water be put in contact with the leaves, they will absorb it for the nourishment of the plant. The experimenter thus educes the fact that the action of the leaf is a vicarious and not a natural function.

Carbolic Acid from Plants.—M. Broughton, government chemist, attached to the cinchona-plantations of Ootacamund, in India, has obtained carbolic acid from the Andromeda Leschmantii, a plant which grows there abundantly. The product is less deliquescent than that obtained from coal-tar, and, owing to the expense attending its preparation, is not likely to compete with the article at present in the market.