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Page:Popular Science Monthly Volume 35.djvu/593

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sary. The best nurses are the calmest nurses, and they are very seldom the ones who suffer most at the sight of their patients' suffering; and "one of the great advantages which patients feel on entering a hospital is that their sufferings do not come back reflected from the faces of those around them; that the sympathy they excite is only a mild sympathy, and not one which heightens their own pain. . . . Hardly a sufferer exists who is not the better instead of the worse for seeing that those around him are not overwhelmed by his sufferings—that, so far as he can go out of himself at all, he may get a little relief by entering into the less overshadowed lines around him, and tasting indirectly another's enjoyments."


A Theory of Volcanic Action.—Mr. J. Logan Lobley explained in the British Association last year a theory of the causes of volcanic action which he had reached while keeping in view forty-two leading and controlling facts. His conclusions are, that the primary cause of the formation of lava is the internal heat of the globe inducing chemical action in subterranean regions when the materials and conditions are both favorable; that since the fusion-point of solids is raised by extreme pressure, the conditions for chemical action may be changed by the removal of vertical pressure or its relief by lateral or tangential pressure; that certain substances are fusible at low or moderate temperatures, and that thus at very moderate depths chemical action may be locally commenced that will extend until sufficient heat is produced to effect rock-fusion; that the cause of the ejection of lava from its source, and of its rise in the volcanic tube, is the increase of bulk consequent upon the change from the solid to the fluid state, aided by the formation of potentially gaseous compounds by chemical reactions among the original materials of the magma; that the ascent of the lava in the volcanic tube may be affected by the weight of the atmosphere and by lunar attractive influence; that the explosive effects of volcanic eruptions are altogether secondary, and are due to the access of sea and land water to fissures, by percolation through cool rocks, up which lava is ascending; that this water, when converted into steam, opens, by its expansive power, rents that admit large flows of sea-water to the lava, occasioning the formation of vents and the greater explosive phenomena of eruptions. The formation of the actual surface volcano and the determination of its position are therefore due to the sea, near which volcanoes are almost always situated. Emissions of lava without explosive effects are from volcanic tubes to which large flows of water have not obtained admittance; and, on the other hand, purely explosive eruptions, without lava-flows, are caused by water reaching lava which fails to rise to the surface of the earth.


Fire-proof Houses in Buenos Ayres.—They build fire-proof houses in Buenos Ayres and Montevideo without thinking of it, and while using all the wood they can afford to; and they use neither iron nor the arch. Trees are scarce in the neighborhood, and timber has to be brought down from the upper waters in hard woods. Being dear, a little of it is made to go as far as possible. The floors and the roofs are supported by joists of hard wood, as among us; across these are laid flat rails of the same, and the spaces between these are bridged over by thin bricks thirteen inches and a half long, with their ends resting on the rails; another layer of bricks is then laid with lime, and generally on this a layer of flat tiles. The doors and windows have no boxes, but simply frames, which are set up when the walls are going up, and built in. There is no lathing, or wainscot, or skirting of the bottom of the walls. A house thus built can not be burned.


Glass-Blowing by Machinery.—A system for glass-blowing by machinery, under which mouth-blowing is dispensed with, has been devised by Mr. Howard M. Ashley. In the machine, the molten metal is delivered into a receptacle called a parison, which holds just enough metal to form a bottle. At the bottom of the receptacle is a collar mold, which forms the ring around the mouth. The central portion of the mold—which may be described as a punch within a punch, from the method in which it works up into the molten glass to make the collar—is hollow, and is connected with a reservoir of compressed air. After the collar is molded, the mold is turned upside down, a little air