The London, Edinburgh and Dublin philosophical magazine and journal of science . ional tothe pressure above 0*5 mm. The gradient at the negativeend of the positive column, and including the Faraday darkspace (E—D), is very much less than anywhere else in thedischarge, and seems almost to vanish at a pressure of about0*65 mm. In Tables IX. to XIV. we pass on to the results obtained bypumping down to any required exhaustion and then graduallyheating up the cathode, the actual pressure being measuredand recorded at intervals. As the volume of the discharge-tube bore but a small ratio to that of t
The London, Edinburgh and Dublin philosophical magazine and journal of science . ional tothe pressure above 0*5 mm. The gradient at the negativeend of the positive column, and including the Faraday darkspace (E—D), is very much less than anywhere else in thedischarge, and seems almost to vanish at a pressure of about0*65 mm. In Tables IX. to XIV. we pass on to the results obtained bypumping down to any required exhaustion and then graduallyheating up the cathode, the actual pressure being measuredand recorded at intervals. As the volume of the discharge-tube bore but a small ratio to that of the pump cylinder,McLeod gauge, and P205 bulb, the heating of the cathodeonly produced trifling changes of pressure, and it has beenshown already that the cathode fall is hardly affected by 694 Mr. J. A. Cunningham on tlte slight changes of pressure except at very high very high temperatures and low pressures the slight leakdid, however, produce quite appreciable effects, as is wellillustrated by the latter part of Table XIV. Fig. 3.—(Temperature = 1500° C.). 0 -I ? -5 -4 b mm. of Mercury \§ 1-5. Pressure. cv 2-5 Table IX. Temperature ofCathode K. 1 Potential Difference. Current. -r, .Pressure, E-A. Defln. of Amps. Mercury. Defln. ° C. K-A. K — E. (calculated) Galvanr. X104. 168 468 793 336 457 25-2 84 5-8 195 320 2-7 102 804 324 480 25-2 8-4 7-8 248 318 163 455 | 804 330 474 197 532 ... 340 20-2 545 1 - 337 1-8 ! 463 1112 306 26-9 8-97 55-3 1255 747 302 445 59-3 1325 752 300 452 67-3 1463 793 296 497 70-3 1514 798 294 504 265 8-83 Discharge of Electricity through X. 695 Temperature ofCathode. Potential Difference. Current. iPressure,! 1 Defln. °C. K-A. 787 K-D. D-A. Defln. Amps. xio4. Hg. 80-3 1681 350 437 1-9 78-6 1653 798 358 440 73-4 1566 793 362 431 53-3 1220 770 366 404 52-3 1202 770 360 410 24-8 650 782 373 409 198 535 390 , 193 524 804 400 404 24-9 8-30 10 305 815 455 360 7 °27 420 5 173 410 4 ]42 420 2-8 105 ? 450 24-1 8-03 Table XI.
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