. A manual of electro-static modes of application, therapeutics, radiography, and radiotherapy . Scale /a Fig. 6. automatic feed by means of which the active electrode alwaysrests against a glass stop, descending by gravity as it is con-sumed. To obviate overheating or make the heating muchslower, extra large jars are employed with this electrolytic interrupters are invaluable for rapid radi-ography because they permit the passage of a large volume ofcurrent through the tube. Various types of mechanical interrupters are in common use, X-RAY APPARATUS. 175 and, though permitting
. A manual of electro-static modes of application, therapeutics, radiography, and radiotherapy . Scale /a Fig. 6. automatic feed by means of which the active electrode alwaysrests against a glass stop, descending by gravity as it is con-sumed. To obviate overheating or make the heating muchslower, extra large jars are employed with this electrolytic interrupters are invaluable for rapid radi-ography because they permit the passage of a large volume ofcurrent through the tube. Various types of mechanical interrupters are in common use, X-RAY APPARATUS. 175 and, though permitting less rapid interruptions, serve a prac-tical purpose. The objection to them, however, is that theyrequire metal terminals which, if not of platinum, are rapidlydestroyed, and eventually the platinum tips are also used mercury-jet interrupter, one of the most recent and besttypes, has the disadvantage that the oxidation of the mercury. Fig. 7.—Crookes Tube. necessitates frequent cleaning. A motor is necessary foroperating this type of interrupter. Another coil is providedwith parallel disks, which can be regulated in distance to thecurrent employed, giving a rapid spark interruption. The diskis provided with a vessel filled with water placed over the platefor cooling. The disks become oxidized, requiring frequentcleaning, or an intermittent, irregular interruption of these interrupters can be considered perfect, but theypractically meet the requirement, and, with requisite care andattention to details, answer the purpose. Of Crookes tubes, the earliest type was described by SirWilliam Crookes before the British Medical Association, 1879,a cut of which is shown in Fig. 7. These tubes were con-structed with the cathode of aluminum, having a plane, not con-cave, surface, as in the tubes now in general use. With thesetubes, the glass side of the tube opposite the cathode was theanti-cathode, from which the
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