PROGEESS IN PHYSICS. 331 



scnted; the publication of Lord Rayloigh's treatise; the invention and 

 construction by Konig of acoustic apparatus, the best example yet 

 furnished of scientific handicraft. All of these mark important 

 advances, not only in acoustics, but in general physics as well. The 

 phonautograph of Scott and Konig, by which a graphic record of the 

 vibrations of the vocal cords was made possible, was ingeniously con- 

 verted by Edison into a speech recording and reproducing machine, 

 the phonograph, by which the most marvelous results are accomplished 

 in the simplest possible manner. 



The century is also to be credited with the discovery and develop- 

 ment of the art of photography, which, although not of the first 

 impoi'tance, has contributed much to the pleasure of life, and as an aid 

 to scientific investigation has become quite indispensable. 



The wonderf ulh^ beautiful experiments of Sir William Crookes, on 

 the passage of an electric discharge through a high vaciuim, and other 

 phenomena connected with what has been called ''radiant matter," 

 begun about a quarter of a century ago and continued by him and 

 others up to the present time, laid the foundation for the brilliant 

 work of Rontgen in the discovery and study of the so-called "X" 

 rays, the real nature of which is not yet understood. Their further 

 investigation by J, J. Thomson, Becquerel, and others seem to have 

 revealed new forms and phases of radiation, a fuller knowledge of 

 which is likely to throw much light on obscure problems relating to 

 the nature of matter. 



Concerning the nature of matter, the ablest physicists of the cen- 

 tury have thought and written much, and doubtless our present knowl- 

 edge of the subject is much more nearly the truth than that of a hun- 

 dred years ago. The molecular theoiy of gases has met with such 

 complete experimental verification and is so in accord with all observed 

 phenomena that it must be accepted as essentially correct. As to the 

 ultimate nature of what is called matter, as distinguished from the 

 ethereal medium, what is known as the "vortex theory of atoms" has 

 received the most consideration. This theory was developed by Lord 

 Kelvin out of Helmholtz's mathematical demonstration of the inde- 

 structibility of a vortex ring when once formed in a medium possess- 

 ing the properties which are generally attributed to the ether. 



Perhaps the most remarkable as well as the most promising fact 

 relating to physical science at the close of the nineteenth century is 

 the great and rapidly increasing number of well-organized and splen- 

 didly equipped laboratories in which original research is systematically 

 planned and carried out. When one reflects that for the most part 

 during the century just ending the advance of science was more or less 

 of the nature of a guerrilla warfare against ignorance, it seems safe to 

 predict for that just beginning victories more glorious than any yet won. 



