Sepiembkb 21, 1900.] 



SCIENCE. 



421 



portion of it is in actual transit. When 

 the tension of the alternations is high, the 

 amount of electricity that has to oscillate 

 backwards and forwards on the guiding 

 wires is proportionately diminished, and 

 the frictional waste reduced. At the ter- 

 minals the direct transmission from one 

 armature of the motor to the other, across 

 the intervening empty space, at once takes 

 us beyond the province of the pushing and 

 rubbing contacts that are unavoidable in 

 mechanical transmission ; while the perfect 

 symmetry and reversibility of the arrange- 

 ment by which power is delivered from a 

 rotatory alternator at one end, guided by the 

 wires to another place many miles away, 

 where it is absorbed by another alternator 

 with precise reversal of the initial stages, 

 makes this process of distribution of energy 

 resemble the automatic operations of nature 

 rather than the imperfect material connec- 

 tions previously in use. We are here deal- 

 ing primarily with the flawless continuous 

 medium which is the transmitter of radiant 

 energy across the celestial spaces ; the part 

 played by the coarsely constituted material 

 conductor is only that of a more or less im- 

 perfect guide which directs the current of 

 sethereal energy.- The wonderful nature of 

 this theoretically perfect, though of course 

 practically only approximate, method of 

 abolishing limitations of locality with re- 

 gard to mechanical power is not diminished 

 by the circumstance that its principle must 

 have been in some manner present to the 

 mind of the first person who fully realized 

 the character of the reversibility of a 

 gramme armature. 



In theoretical knowledge a new domain, 

 to which the theory as expounded twenty 

 years ago had little to say, has recently 

 been acquired through the experimental 

 scrutiny of the electric discharge in rarefied 

 gaseous media. The very varied electric 

 phenomena of vacuum tubes, whose electro- 

 lytic character was first practically estab- 



lished by Schuster, have been largely re- 

 duced to order through the employment of 

 the high exhaustions introduced and first 

 utilized hj Crookes. Their study under 

 these circumstances, in which the material 

 molecules are so sparsely distributed as but 

 rarely to interfere with each other, has 

 conduced to enlarged knowledge and veri- 

 fication of the fundamental relations in 

 which the individual molecules stand to all 

 electric phenomena, culminating recently 

 in the actual determination, by J. J. Thom- 

 son and others following in his track, of the 

 masses and velocities of the particles that 

 carry the electric discharge across the ex- 

 hausted space. The recent investigations 

 of the circumstances of the electric dissoci- 

 ation produced in the atmosphere and in 

 other gases by ultra-violet light, the Eont- 

 gen radiation, and other agencies, constitute 

 one of the most striking developments in 

 experimental molecular physics since Gra- 

 ham determined the molecular relations of 

 gaseous diffusion and transpiration more 

 than half a century ago. This advance in 

 experimental knowledge of molecular phe- 

 nomena, assisted by the discovery of the 

 precise and rational eifeet of magnetism on 

 the spectrum, has brought into prominence 

 a modification or rather development of 

 Maxwell's exposition of electric theory, 

 which was dictated primarily by the re- 

 quirements of the abstract theory itself; 

 the atoms or ions are now definitely intro- 

 duced as the carriers of those electric 

 charges which interact across the sether, 

 and so produce the electric fields whose 

 transformations were the main subject of 

 the original theory. 



We are thus inevitably led, in electric 

 and Eethereal theory, as in the chemis- 

 try and dynamics of the gaseous state 

 which is the department of abstract phys- 

 ics next in order of simplicity, to the con- 

 sideration of the individual molecules of 

 matter. The theoretical problems which 



