. Radiography, X-ray therapeutics and radium therapy . s metal is employed are capableof withstanding the severe treatment to which they are subjected on thesingle-impulse method, and it was further found that these tubes can beprovided with a sharp focus. Further, as a thick block of tungsten can beused as anti-cathode, such tungsten tubes have an almost unlimited life,whilst platinum tubes are destroyed after several flashes. APPARATUS FOR TIME AND RAPID RADIOGRAPHY 9 It was also observed that in consequence of the advantages mentionedabove, the tungsten tubes give photographs which are rich
. Radiography, X-ray therapeutics and radium therapy . s metal is employed are capableof withstanding the severe treatment to which they are subjected on thesingle-impulse method, and it was further found that these tubes can beprovided with a sharp focus. Further, as a thick block of tungsten can beused as anti-cathode, such tungsten tubes have an almost unlimited life,whilst platinum tubes are destroyed after several flashes. APPARATUS FOR TIME AND RAPID RADIOGRAPHY 9 It was also observed that in consequence of the advantages mentionedabove, the tungsten tubes give photographs which are richer in contrastand deeper than those obtained with tubes with platinum cathode. The Snook apparatus was the first interrupterless machine made ina practical form for X-ray work, and was first introduced and made in Eng-land in 1907, the credit of the design being entirely due to Mr. H. ClydeSnook of Philadelphia. The machine consists essentially of three parts : the motor converter,the high-tension transformer, and the high-tension rectifier or commu-. Fig. 4.—Snook apparatus. (Newton and Wright.) tator. In the case of the machine designed to run on continuous current,the part first named consists of a motor usually about 4 k. w. in size, which runsfrom the main at about 1500 revolutions per minute. This machine has apair of so-called slip rings, from which can be obtained an alternating current. This alternating current is connected to the primary circuit of thetransformer, through a controlling rheostat, and is raised in electrical pressureor voltage to the necessary tension for X-ray work. This high-tension current is, however, alternating in character, whereasfor the production of X-rays it is necessary to have a discharge in one direc-tion only, and the latter is obtained by means of the high-tension rectifier. 10 RADIOGRAPHY This consists of a number of ebonite tubes, through which conductorspass, mounted on an axis, and rotated by the motor converter. In revolving the c
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