Page:Popular Science Monthly Volume 47.djvu/291

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ciation, have been observed from the very earliest times, and are so great that they can be detected with very simple apparatus. These effects are due to exterior causes, and consist in a displacement of the axis of the earth in space, and a consequent wandering of the pole among the stars. The action of internal forces in the earth would be to produce a displacement in the rotating body itself. A deviation of the rotational axis from the principal axis of inertia would cause a rotation of the pole round the principal axis of inertia. Such a rotation would have a period of nearly ten months, and could be best detected by continuous and active observations of latitude at various observatories. Measurements were made as early as the middle of this century, but gave no definite results, the ten-monthly period being marked by other disturbances due to currents and circulations in the atmosphere, oceans, and rivers. Four years ago the International Geodetic Union secured co-operation of observations, and this, together with an expedition to Honolulu, has led to definite results. These show that the north pole wanders through about fifty feet between its extreme positions.

Bactericidal Solar Rays.—Although investigation has not been idle, experimenters have not been wholly agreed as to the exact property or field of the sun's rays which is most efficient in action on bacteria and fungi. The inquiry has been continued by Prof. H. Marshall Ward, to whom the thought occurred in the course of his work that the most direct answer to the question, Which rays are the most effective ones? might be best obtained by shining the solar spectrum directly upon the film of spores, and making it record the effects by their subsequent behavior, according as the different groups of rays fell upon them—in other words, by obtainiug a photograph of the spectrum in living and dead bacteria. The results showed conclusively that the rays that kill the bacteria are the blue and violet ones. An observation was made during the investigation which may go far to account for the unsatisfactory character of the determinations of former experiments. The chief difficulty to be overcome was the great weakening of the intensity of the dispersed rays of the beam of light decomposed to form the spectrum—a weakening caused by the distribution of the incidence of the rays over a larger area and by their absorption and reflection in passing through the lenses and prisms. It was found also, in working with the electric light, that the power of the blue and violet rays was further impaired—in other words, that they were stopped—by the material (glass) through which they had to pass. The effect of the glass was practically the same as that of mist or haze in the atmosphere, which so filters out the blue-violet rays that the light of a dull day was of little effect in the author's experiments. These difficulties were overcome by using quartz instead of glass, with which it was possible to obtain a very pure spectrum sufficiently rich in blue and violet rays to kill the spores in a few hours. The author found it easy to obtain satisfactory results in the summer with the solar rays, even with glass lenses, mirrors, etc., and exposures of five or six hours, but in winter the exposures required to be so long as to be almost impracticable.

Work of the Peabody Museum.—The Curator of the Peabody Museum of American Archæology and Ethnology calls attention, in his report for 1893-'94, to the lack of room in the museum. Several collections made under the curator's direction have been secured. Besides a generous gift of money, Mr. Clarence B. Moore has contributed a good representative collection of the singular pottery which he obtained from a mound in Florida, and other objects of interest from the burial and shell mounds of that State. The publication of Mr. Nuttall's memoir has been provided for, and the work has been held in press for the incorporation of newly discovered facts. Space has been provided for the collections of archæological, historical, and educational objects and relics made by the late Mrs. Hemenway, of which Mr. J. Walter Fewkes is in charge. The collection of Mr. Frederick H. Rindge, deposited in the museum, contains the finest and most extensive lot of obsidian implements ever brought together from the Klamath country. Some of the chipped implements are remarkable for their size, and others for their beautiful finish. The collection also includes gems of workmanship in stone, bone, and ivory