The London, Edinburgh and Dublin philosophical magazine and journal of science . orm of focus-tube was brought out, a tube which for photographic purposeswas found superior to any other form, and has not yet beensurpassed. 3. Observing in some of these experiments that the metalspade used as antikathode became red-hot, a special tube wasconstructed for me by Mr. Gardiner to test the question* whether the high temperature of the antikathode was, or wasnot, prejudicial to the emission of #-rays. This special tube(fig. 3) was furnished with an antikathode of platinum-foilmounted so that while ser
The London, Edinburgh and Dublin philosophical magazine and journal of science . orm of focus-tube was brought out, a tube which for photographic purposeswas found superior to any other form, and has not yet beensurpassed. 3. Observing in some of these experiments that the metalspade used as antikathode became red-hot, a special tube wasconstructed for me by Mr. Gardiner to test the question* whether the high temperature of the antikathode was, or wasnot, prejudicial to the emission of #-rays. This special tube(fig. 3) was furnished with an antikathode of platinum-foilmounted so that while serving both as antikathode and asanode it could be heated by passing a current through itfrom an auxiliary battery. Observing the activity of thetube by means of a luminescent screen of platinocyanide ofpotassium, it was found that the heating of the antikathode,so far from being disadvantageous, decidedly promoted the 164 Dr. Silvanus P. Thompson on emission of *r-rays, and increased the continuity and brilliancyof the luminescence. Various amounts of current were sent Fig. through the platinum, the most effective result being obtainedby currents which heated the surface to visible the effect is a direct one or an indirect owing to thedriving out of occluded gases is not yet determined. 4. When watching with the luminescent screen the emis-sion of #-rays within bulbs connected with the pump, someobservations were made of direct importance with regard tothe state of exhaustion that is best. The degree of vacuumwhich suffices for the production of kathodic shadows isknown not to be sufficient for the production of ^-rays. It isalso known that when evacuation is pushed very far theinternal resistance of the bulbs rises very high, so that theybecome almost non-conductive. If a bulb is exhausted, andheated during exhaustion, and the vacuum pushed almost tonon-conductivity, and if a little air is again admitted and thetube again exhausted, the high degree of vacuum
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Keywords: ., bookcentury1800, bookdecade1840, bookidlondon, booksubjectscience
