694 ^^-^ POPULAR SCIENCE MONTHLY. 



delicacy of tlie tasimeter was demonstrated unmistakably. Langley's 

 heat-measurer is scarcely less sensitive, and probably more manage- 

 able. 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 auto- 

 matic 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 re- 

 sponse 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 in- 

 stantaneous electric lighting ; could signal the engineers to stop and 

 reverse the engines, or even stop and reverse the engines automati- 

 cally. 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 ob- 

 taining 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. 



