SPARK SPECTRA OF METALS.
A very simple method of observing the speetta of metals is to make a spark gap filled with other gases than air, to exil amine the effect of these on the spark,1 The pressure of the enclosed gases can also be varied. A indicates the adjusting screw.
INTErtatITTING THE CURRENT.
One of the most important things to notice is the effect of temperature. The amount of energy given out at the spark gap depends on the product of the volt age and current there. This can be altered by varying the periodicity of the vibrating armature as described pre viously, by altering the length of the spark gap. or by having an auxiliary adjustable spark gap in series in the secondary circuit. In the more expensive forms of induction coils the interrupter is either electrolytic in character, like the Wehnelt break, in which the interruptions are caused by bubbles of liberated hydro gen, or of the mercury type, in which a revolving plate, with symmetrically placed.
apertures, is attached to a motor. The olate breaks a conducting jet of mercury which forms part of the primary circuit 2. large number of times per second. The rate of interruption of the current can be adjusted at the motor. The stream of mercury is kept constantly flowing by means of a centrifugal pump also worked by the motor. The Wimshurst influence machine may also be used for this work, if desired, and if the Leyden jars attached to the primary circuit are of a large size, the quantity of electricity discharged at each spark is correspondingly large. An alternating current of very high periodi city may be passed through the primary coil, in which case no interrupter is re attired.