The Astrophysical journal . as fol-lows. A copper wirewas placed opposite tothe incandescent fila-ment of a very smallelectric lamp, at adistance of 6 mm; thiscopper wire served ascathode, the incan-descent carbon fila-ment as anode. On this there will be produced some positive ions in consequenceof the high temperature; and these will be driven to the cathodeby the potential difference, AF, between the electrodes; whenthe gas-pressure is low they will traverse this drop in potentialfreely—i. e., without collision—and will strike the surface of thecathode, with high speed, as canal rays. It is
The Astrophysical journal . as fol-lows. A copper wirewas placed opposite tothe incandescent fila-ment of a very smallelectric lamp, at adistance of 6 mm; thiscopper wire served ascathode, the incan-descent carbon fila-ment as anode. On this there will be produced some positive ions in consequenceof the high temperature; and these will be driven to the cathodeby the potential difference, AF, between the electrodes; whenthe gas-pressure is low they will traverse this drop in potentialfreely—i. e., without collision—and will strike the surface of thecathode, with high speed, as canal rays. It is evident that forsmall potential differences the current will be small and nearly satu-rated. At the velocity corresponding to about 340 volts, however,the positive ions, by the suddenness of their impact upon the cathode,begin to create new ions; and hence the current suddenly rises tolarge values. It would thus appear that canal rays when moving with a speed 1 J. Stark, Verkandl. d. deutsch. phys. Ges., 6, 104, Difference of potential between cathode and negativeend of thread Fig. 10 172 /. STARK less than a certain limit (300 to 500 volts) are unable to ionize a gasby collision; with higher velocities, however, the gas is ionized. Inthe spectroscopic observations here described the cathode-dropalways exceeded 1000 volts, so that the canal rays were capable ofionizing the gas behind the cathode, thus giving opportunity for thereunion of positive and negative ions, and hence, in terms of ourhypothesis, for the emission of a banded spectrum. This radiation,then, has its origin in the potential energy which is set free by thereunion; it is an indirect consequence of the collision of the canalrays with the neutral atoms of the gas; the more frequent these colli-sions—i. e., the greater the gas-pressure—the more intense is thebanded spectrum in the region traversed by the canal rays. It has already been established, in §3, that the line-spectrum ofthis same region
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectspectru, bookyear1895
