Another method of cleaning the emulsion is to wash it in  an open jar placed under a tap. and let the washings settle  for a week.

To avoid this inconvenience, many recent types of break are  constructed so as to employ gas as a dielectric.

(b) The turbine or jet type of break has an action indicated somewhat by its name. When such a break is sot in  motion, a jet of mercury is by centrifugal action propelled  radially from a central stem, and makes contact with a rapid  succession of peripheral sectors of metal, having between  them intervals of insulating material.

The succession of makes and breaks is obtained by a rotary  motion of either the central stem carrying the radial jet with  it, or of the peripheral sectors while the jet is in a fixed direc-  tion. In the earlier and more common designs, speed and  rate of interruption can be directly regulated by altering the  current sent to the driving motor. The metal sectors can be  varied in number to secure a similar regulation, and these  sectors are further made of a triangular shape, so that verti-  cal adjustment may vary the width of metal exposed to the*  jet, and consequently the duration of contact. The surface  of the mercury is in this form of break, as in the dipper type,  covered by some insulating and spark-extinguishing liquid,  paraffin being here usually employed.

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