SCIENCE IN RELATION TO THE ARTS. 223 



electrical discharges through rarefied gases must be an essential ele- 

 ment of every disruptive discharge, and that the phenomena of strati- 

 fication might be regarded as magnified images of features always 

 present, but concealed under ordinary circumstances. It was with a 

 view to the study of this question that the researches by Moulton and 

 myself were undertaken. The method chiefly used consisted in intro- 

 ducing into the circuit intermittence of a particular kind, whereby one 

 luminous discharge was rendered sensitive to the approach of a con- 

 ductor outside the tube. The application of this method enabled us 

 to produce artificially a variety of phenomena, including that of strati- 

 fication. We were thus led to a series of conclusions relating to the 

 mechanism of the discharge, among which the following may be men- 

 tioned : 



" 1. That a stria, with its attendant dark space, forms a physical 

 unit of a striated discharge ; that a striated column is an aggregate of 

 such units formed by means of a step-by-step process ; and that the 

 negative glow is merely a localized stria, modified by local circum- 

 stances. 



" 2. That the origin of the luminous column is to be sought for at 

 its negative end ; that the luminosity is an expression of a demand for 

 negative electricity ; and that the dark spaces are those regions where 

 the negative terminal, whether metallic or gaseous, is capable of ex- 

 erting sufficient influence to prevent such demand. 



" 3. That the time occupied by electricity of either name in trav- 

 ersing a tube is greater than that occupied in traversing an equal 

 length of wire, but less than that occupied by molecular streams 

 (Crookes's radiations) in traversing the tubes. Also that, especially in 

 high vacua, the discharge from the negative terminal exhibits a dura- 

 tional character not found at the positive. 



" 4. That the brilliancy of the light with so little heat may be due 

 in part to brevity in the duration of the discharge ; and that, for action 

 so rapid as that of individual discharges, the mobility of the medium 

 may count as nothing ; and that for these infinitesimal periods of time 

 gas may itself be as rigid and as brittle as glass. 



" 5. That striae are not merely loci in which electrical is converted 

 into luminous energy, but are actual aggregations of matter. 



" This last conclusion was based mainly upon experiments made 

 with an induction-coil excited in a new way viz., directly by an alter- 

 nating machine, without the intervention of a commutator or con- 

 denser. This mode of excitement promises to be one of great impor- 

 tance in spectroscopic work, as well as in the study of the discharge in 

 a magnetic field, partly on account of the simplification which it per- 

 mits in the construction of induction-coils, but mainly on account of 

 the very great increase of strength in the secondary currents to which 

 it gives rise." 



These investigations assume additional importance when we view 



