Page:Popular Science Monthly Volume 46.djvu/439

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cise means for measuring the diameters of planets or determining their magnitude. Nothing is more ingenious than his explanation of the scintillation of stars, based upon the remarkable properties Fresnel found to be possessed by rays of light. Arago ought truly to be considered as the founder of a branch of astronomy—physical astronomy—that has since been remarkably extended, for it was he who pointed out the importance that would accrue from the application of photography to the study of celestial bodies. He was not able to see the day, however, when chemistry would enter into the domain of astronomy, and we should be able to discover their constitution; spectrum analysis has been discovered, in fact, only since the death of Arago." Arago is besides credited with having conceived the idea of drawing a unit of measurement from the light rays—an idea which has been realized by Mr. Michelson, of the American Bureau of Weights and Measures.

Value of the Nasal Index.—In Mr. H. H. Risley's examination of the characteristics of the natives of northern India, the nose, instead of being vaguely described as broad or narrow, is accurately measured, and the proportion of the greatest width to the greatest length (from above downward), or the "nasal index" (which must not be confounded with the nasal index as defined by Broca upon the skull), gives a figure by which the main elements of the composition of this feature in any individual may be accurately described. The average of mean nasal indices of a large number of individuals of any race, tribe, or caste offers means of comparison which bring out most interesting results. By this character alone the Dravidian tribes of India are easily separable from the Aryan. Even more striking is the curiously close correspondence between the gradations of racial type exhibited by the nasal index and certain of the social data ascertained by independent inquiry.

Public Reservations in Massachusetts.—The Trustees of Public Reservations of Massachusetts received no new trusts during 1893, but they are able to record two movements instituted by the State Legislature, at their suggestion, for the better conservation of certain scenery. A bill was passed providing for the acquisition by the people of Provincetown of all the occupied parts of the province lands at the extremity of Cape Cod, and the permanent reservation of all the remaining portion (about two thousand acres) in the charge of the State Commissioners of Harbors and Lands. Another act creates a permanent Metropolitan Park Commission, With the power of eminent domain and authority to spend one million dollars in buying lands, as well as to accept gifts of land or of money to buy them with, lying within the metropolitan district. This commission has already received twelve thousand five hundred dollars from Mrs. Elish Atkins and her son toward the purchase of the "Beaver Brook reservation," in which are iucluded Beaver Brook Falls, celebrated by Lowell in one of his early poems, and the famous "Great Oaks," which the board of trustees had failed to acquire for want of the power of eminent domain.

Importance of Ocean Currents.—The very bulk of the ocean, Captain W. J. L. Wharton remarks, in his geographical address before the British Association, as compared with that of the visible land, gives it an importance possessed by no other feature on the surface of our planet. Mr. John Murray has shown that its cubical extent is probably about fourteen times that of the dry land. The most obvious feature of the ocean is the constant horizontal movement of its surface waters. It may now be safely held that the prime motor of the surface currents is the wind—not the wind that may blow, and even persistently l)low, over the portion of water that is moving, more or less rapidly, in any one direction, but the great winds that blow predominently from some general quarter over vast areas. These, combined with deflections from the land, settle the main surface circulation. The trade winds are the prime motors. They cause a surface drift of no great velocity over large areas in the same general direction as that in which they blow. The westerly winds that prevail in higher northern and southern latitudes are next in order in producing great currents. From the shape of the land they in some cases