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Page:Popular Science Monthly Volume 48.djvu/387

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THE GEOLOGICAL WORK OF THE AIR.

THE GEOLOGICAL WORK OF THE AIR.
By M. STANISLAS MEUNIER.

SOME specimens recently received at the geological laboratory of the National History Museum in Paris suggest a study of the action of the wind in geology and of the importance, long overlooked, of wind deposits. The specimens are lavas from the volcano Mauna Loa, which the wind, lashing them before hardening, has reduced to fibers of extraordinary fineness. They might be called bunches of oakum. The mechanism of the formation of these—or Pélé's hairs, or bald men's locks, as they are poetically called—is similar to that by which similar formations are produced in furnaces when the blast is directed against the melted slags. It has been proposed to employ the product thus prepared as a textile material; but it is not well adapted to such use, be

PSM V48 D387 Pele hairs from mauna loa vulcano hawaii.jpg
Fig. 1.—Pélé's Hairs: Volcanic Lavas spun by the Wind and resembling Tow; from the Volcano Mauna Loa, Sandwich Islands. Natural size.

cause of frequent abrupt changes in the diameter of the vitreous threads. This peculiarity is shown in Fig. 1, where the little black tears mixed in with the brownish fibrous material are really the knots by which the filaments may at any time be interrupted. If we examine these bald men's locks with a microscope, we shall find the evidences of their wind origin more abundant. Fig. 2 represents them magnified fifteen diameters, and Fig. 3 one hundred diameters. We see in the former of these figures that, notwithstanding their coarse appearance, the filaments are anything but homogeneous in all their parts. The axial region of each of