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SCIENCE. 



[N. S. Vol. XVI. No. 402. 



vestigation, has steadily advanced into the 

 unknown; secondly, his progress has been 

 an acceleration which has been increasing 

 in its rate from the beginning; thirdly, all 

 progress has been made by a continuity of 

 path which indicates no limit to its reach; 

 finally, we know that the various fields of 

 scientific work are all exhibiting, as far as 

 we have gone, a perfect continuity. It 

 would seem most probable, if not absolutely 

 certain, that, once we have secured a foot- 

 hold upon any new field, we may anticipate 

 complete ultimate exploration. Once we 

 have gained firm hold upon any one link in 

 the logical chain of law controlling any 

 class of phenomena, we may expect to be 

 able, in due time, to pass, link by link, to 

 either end, or, if endless, either through its 

 cyclical configuration or indefinitely to- 

 wards its infinity of development, and 

 to gain as much of its length as finite time 

 may permit. So much may we prophesy. 



It is also true that scientific investiga- 

 tion and general observation show that the 

 process of scientific deduction is always 

 as simple and as direct as a child's logic. 

 It necessarily depends upon the following 

 of a chain of reasoning, based upon inter- 

 linked, ascertained, facts, every step from 

 link to link of which is an axiomatic deduc- 

 tion. This is true of all reasoning, and in 

 no department of human knowledge or in- 

 vestigation is this a more absolute and im- 

 perative general condition of assurance of 

 certainty of results than in each step in 

 scientific research. 



When it was first observed that the glow- 

 worms and the fire-flies produced a light 

 within their own bodies, it became an 

 axiomatic inference that it was a 'cold 

 light ' and that it could not be accompanied 

 by any heat of higher temperature than 

 that of the cold-blooded creature from 

 which it emanated. When Langley proved 

 by means of his bolometer that the light 

 of the fire-fly, instead of producing a 



candle-temperature of 2000° Fahr. (above 

 1100° C.) was quite free from sensible 

 heat, it became obvious that this must be 

 the 'cheapest form of light' and that, could 

 we find a way of imitating nature in this 

 direction, instead of wasting 99 per cent, 

 or more of our expended energy, as in the 

 ordinary gas-flame, we might secure nearly 

 a hundred times as much light from the 

 same cost in energy supplied, and thus 

 practically without waste.* As stated by 

 Langley and Very, this light 'is a result of 

 certain chemical combinations and nothing 

 forbids us to suppose that it may some 

 day be produced by the processes of the 

 laboratory.' Perhaps we may go further 

 and say that, as a product of a chemical 

 process, it may prove to be possible to 

 reproduce it by the direct application of 

 the elementary energies which there oper- 

 ate. This is one of the great problems still 

 challenging the chemist, the electrician and 

 the engineer. It will be solved when we 

 learn to produce any part of the spectrum, 

 heat and light in any proportion, from 

 zero to unity, at will. 



Nature's 'cheapest light,' according to 

 Langley and Very, involves heat-production 

 about one four-hundredth that of the can- 

 dle-flame and has an insigniflcant cost, 

 so measured, as compared with the most 

 economical light yet employed for indus- 

 trial purposes by man. Nature produces 

 light and almost no heat; man produces 

 light with a hundred times as much energy 

 wasted in form of accompanying heat, even 

 with his best lights. Nature, through an 

 evolution extending over countless cen- 

 turies, millenniums, probably, has brought 

 about the perfection of energy-utilization. 

 Man, guided by nature, should be able, in 



* S. P. Langley and F. W. Very, ' Cheapest 

 Form of Light,' Smithsonian Coll., XLI., 190L S. 

 P. Langley, Science, June 1, 18S3; Proc. National 

 Academy. President's Inaugural, Am. Soc. Mech. 

 Engrs., 1880, E. H. Thurston. 



