SCIENCE AND SAFETY AT SEA. 693 



But, unlike the risk from collision with another ship, the risk from col- 

 lision with icebergs can not be diminished by any system of side- 

 lights or head-lights or stern-lights, except in just such degree (un- 

 fortunately slight) as a powerful light at the foremast-head, aided by 

 strono- side-lights or bow-lights, may serve to render the gleam of the 

 treacherous ice discernible somewhat farther ahead. But to a steam- 

 ship running at the rate of fourteen or fifteen knots an hour, even in 

 the clearest weather, at night, the distance athwart which a low-lying 

 iceberg can be seen, even by the best eyes, is but short. She runs 

 over it before there is time for the watch to make their warning heard, 

 and for the engineers to stop and reverse their engines. 



But science, besides extending our senses, provides us with senses 

 other than those we possess naturally. The photographic eyes of sci- 

 ence see in the thousandth part of a second what our eyes, because in 

 so short a time they can receive no distinct impression at all, are un- 

 able to see. They may, on the other hand, rest on some faintly lumi- 

 nous object for hours, seeing more and more each moment, where ours 

 would see no more perhaps even less after the first minute than they 

 had seen in the first second. The spectroscopic eyes of science can 

 analyze for us the substance of self-luminous vapors or of vapors ab- 

 sorbing light, or of liquids, etc., where the natural eyes have no such 

 power of analysis. The sense of feeling, or rather the sense for heat, 

 which Reid originally and properly distinguished as a sixth sense (not 

 to be confounded, as our modern classification of the senses incorrect- 

 ly confounds it, with the sense of touch), is one which is very limited 

 in its natural range. But science can give us eyes for heat as keen and 

 as widely ranging as the eyes which she gives us for light. It was no 

 idle dream of Edison's, but a thought which one day will be fraught 

 with useful results, that science may hereafter recognize a star by its 

 heat, which the most powerful telescope yet made fails to show by its 

 light. Since that was said, the younger Draper (whose loss followed 

 so quickly and so sadly for science on that of his lamented father) has 

 produced photographic plates showing stars which can not be seen 

 through the telescope by which those photographs were taken. As 

 yet the delicate heat-measurers devised by science have not been ap- 

 plied to astronomical research with any important results. But Edi- 

 son's and Langley's heat-measurers have been used even in this way, 

 and the very failure which attended the employment of Edison's heat- 

 measurer (the tasimeter, or, literally, the strain-measurer, described 

 shortly before in the " Times ") during the eclipse of 1878 shows how 

 delicate is the heat-estimating sense of science. When the light of 

 the corona which has no heat that the thermometer, or even that 

 far more delicate heat-measurer, the thermopile, will recognize fell 

 on the face of the tasimeter, the index which Edison supposed likely, 

 to move just perceptibly actually flew beyond the index-plate. Thus, 

 though the heat of the corona could not be measured, the extreme 



