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Page:Popular Science Monthly Volume 24.djvu/712

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THE POPULAR SCIENCE MONTHLY.

delicacy of the tasimeter was demonstrated unmistakably. Langley's heat-measurer is scarcely less sensitive, and probably more manageable. But in point of fact each instrument is more sensitive than the heat-sense of science is required to be, to do the work I have now to indicate; and an instrument can readily be constructed which shall be, in the right degree, less sensitive than they are, though it might be difficult at present to invent any that should be more senstive.

The sense of sight is not the only sense affected as an iceberg is approached. There is a sensible lowering of temperature. But to the natural heat-sense this cooling is not so obvious or so readily and quickly appreciated that it could be trusted instead of the outlook of the watch. The heat-sense of science, however, is so much keener that it could indicate the presence of an iceberg at a distance far beyond that over which the keenest eye could detect an iceberg at night; perhaps even an isolated iceberg could be detected when far beyond the range of ordinary eye-sight in the day-time. Not only so, but an instrument like the thermopile, or the more delicate heat-measurers of Edison and Langley, can readily be made to give automatic notice of its sensations (so to speak). As those who have heard Professor Tyndall's lectures any time during the last twenty years know, the index of a scientific heat-measurer moves freely in response either to gain or loss of heat, or, as we should ordinarily say, in response either to heat or cold. An index which thus moves can be made, as by closing or breaking electrical contact, or in other ways, to give very effective indication of the neighborhood of danger. It would be easy to devise half a dozen ways in which a heat-indicator (which is of necessity a cold-indicator), suitably placed in the bows of a ship, could note, as it were, the presence of an iceberg fully a quarter of a mile away, and speak of its sensations much more loudly and effectively than the watch can proclaim the sight of an iceberg when much nearer at hand. The movement of the index could set a fog-horn lustily announcing the approach of danger; could illuminate the ship, if need be, by setting at work the forces necessary for instantaneous electric lighting; could signal the engineers to stop and reverse the engines, or even stop and reverse the engines automatically. "Whether so much would be necessary—whether those among lost Atlantic steamships which have been destroyed, as many have been, by striking upon icebergs, could only have been saved by such rapid automatic measures as these—may or may not be the case; but that the use of the infinitely keen perception which the sense-organs of science possess for heat and cold would be a feasible way of obtaining much earlier and much more effective notice of danger from icebergs than the best watch can give, no one who knows the powers of science in this direction can doubt.—London Times.