WHY PROGRESS IS BY LEAPS. 225 



the electric furnace. " Before there can be applied science there 

 must be science to apply," and it is in enabling the investigator 

 to know Nature under a fresh aspect that electricity rises to its 

 highest office. As a case in point, take the bolometer of Prof. S. 

 P. Langley : its delicate wire, sensitive to one millionth of a de- 

 gree centigrade, is moved by minute steps through the invisible 

 areas of the solar spectrum ; each indication of temperature, 

 automatically photographed, comes out in a series of dark and 

 bright lines. This process, repeated with each chemical element, 

 promises that one day the physicist will have before him a full 

 or tolerably complete map of every distinctive spectrum. He 

 can then ask, Given such and such vibrations, how is the body 

 constituted that sent them forth ? much as a musician might try 

 to reason from the tone and timbre of a note to the structure of 

 the instrument which uttered the note. In further uses of pho- 

 tography the physicist, by means of instantaneous contacts, is 

 beginning to find out what goes on in the critical moments when 

 chemical collisions in the voltaic cell are gliding into electric 

 waves an inquiry which bears on the prime question of electric 

 art, namely, how the chemical energy contained in coal can be 

 transformed into a current without the enormous levies imposed 

 by the steam engine. Hertz, in the purely scientific excursion by 

 which he generated electric waves intermediate in length be- 

 tween those of sound and light, came upon a discovery of pro- 

 found interest that, given its appropriate ray, every substance 

 whatever offers it a free and open path. It remained for Prof. 

 Rontgen to complete the proof that certain of these rays, while 

 refusing obedience to the laws of light, can, nevertheless, exert 

 photographic power. His apparatus combines in the happiest way 

 the utmost resources of both the electrician and the photogra- 

 pher ; at a vital point it employs the singular capacity for fluores- 

 cence whereby the compounds of barium and other substances 

 can convert to visibility an otherwise invisible image. Apart 

 from such a triumph as this, rich in possibilities for art and 

 science, the common routine of ascertaining electrical constants 

 has high value in research ; to know the conductivity, polariza- 

 bility, and other electrical properties of matter is to peer at its 

 architecture through new windows ; to detect many of the links 

 which bind atom to atom, molecule to molecule. A new orches- 

 tration of inquiry is possible through the instruments created by 

 the electrician, through the advances in method which these in- 

 struments suggest. Hence to-day a surround is in progress which 

 may early in the twentieth century make atom and molecule as 

 obedient to the chemist as brick and stone are to the builder now. 

 But, however much new knowledge may do with electricity, 

 some of its best work is already done. It is not likely in the f u- 



