. Radiography, X-ray therapeutics and radium therapy . y instep or synchronism withthe current. The apparatus is muchpreferred to an induction Fig. 5.—Diagram of Snook apparatus. (Newton and Wright.) coil by many workers, Owing to the possibility which itaffords of using very heavy currents, enabling practically instantaneousradiograms of any part of the body to be taken, and also on account ofthe ease with which the current can be regulated. The machine, moreover, produces a perfectly unidirectional current,entirely free from any inverse discharge in the wrong direction, which is agreat advan
. Radiography, X-ray therapeutics and radium therapy . y instep or synchronism withthe current. The apparatus is muchpreferred to an induction Fig. 5.—Diagram of Snook apparatus. (Newton and Wright.) coil by many workers, Owing to the possibility which itaffords of using very heavy currents, enabling practically instantaneousradiograms of any part of the body to be taken, and also on account ofthe ease with which the current can be regulated. The machine, moreover, produces a perfectly unidirectional current,entirely free from any inverse discharge in the wrong direction, which is agreat advantage from the point of view of the life and general workingcondition of the X-ray tube. Accumulators If no current from a main is available, accumulators may be usedprovided there is an opportunity of getting them recharged easily; but itmust be understood that the time of exposure required will be muchlonger, because with twelve 2-volt accumulators we cannot produce the sameintense discharge which can be produced with a 100- or 200-volt supply. If. ACCUMULATORS AND DYNAMOS 11 there is no facility for recharging the accumulators, twelve or more largebichromate cells may be used; but if the apparatus is required for use fre-quently, the recharging of bichromate cells is troublesome. In such circum-stances other methods of obtaining a supply of current must be adopted,such as the use of a small gas engine and dynamo. Free negative terminal. 1 i I I t I I 1 I { £ I- * Free positive terminal. Fig. 6.—Accumulator connections. The positive wire going to the coil is connected up with thefree positive terminal of the accumulators and the negative wire with the free negative terminal. A practical point of some importance in the use of accumulators is tosee that they are kept well charged and ready for use. It is also well toremember the mode of connection to the coil and break. The drawing aboveillustrates this point. Dynamos A gas or oil engine can be used to drive a small dynamo.
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