. Radiography and the 'X' rays in practice and theory : with constructional manipulatory details . ification with double spring, which has givengood results in the authors hands, is shown at tig. consists, virtually, of an Ai)ps contact breaker with a second and rather stiffspring attached to the springwhich carries the hammerhead, and on the back of thissecond spring, opposite thecontact screw, is placed theplatinum contact. Whateverform of contact breaker beadopted, it is essential, in viewof the large current which ithas to transmit, as well asthe self-induction spark whicheven the
. Radiography and the 'X' rays in practice and theory : with constructional manipulatory details . ification with double spring, which has givengood results in the authors hands, is shown at tig. consists, virtually, of an Ai)ps contact breaker with a second and rather stiffspring attached to the springwhich carries the hammerhead, and on the back of thissecond spring, opposite thecontact screw, is placed theplatinum contact. Whateverform of contact breaker beadopted, it is essential, in viewof the large current which ithas to transmit, as well asthe self-induction spark whicheven the best condenser doesnot entirely do away with, that the platinum contactsthemselves should be very heavy, and if possiblesurrounded by a considerable mass of good conductingmetal. For this reason the platinum points themselvesshould be of not less than No. 14 ; and in thecase of the spring, if this is embedded in a boss of silverof rather over \ in. in diameter, the likelihood of theplatinum points welding together is greatly diminished.§ 25. A necessary piece of apparatus in connection. Fio. 14.— SpkingContact-Bkeakek. THE INDUCTION COIL 49 with these large coils is the commutator^ or currentreverser, which enables us at will to cut off or reversethe direction of the current sent from the battery throughthe primary of the coil, and consequently to stop orreverse the direction of the main flow of the inducedcurrent in the secondary. A very usual form of com-mutator is shown at fig. 15. It consists of a cylinder
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