527,212. Mercury switches. ADLAKE CO. April 4, 1939, No. 10489. Convention date, April 14,1938. [Class 38 (v)] In a mercury switch in which change in the level of the mercury, produced, e.g., by the movement of an electromagnetically-operated displacer 46, causes mercury to bridge two electrodes 32, 33, the electrodes are mounted in a cup 39 having a small hole 45 through which mercury passes to cause a slow " make " or "break." In the form shown, energization of a magnet 26 raises the displacer 46 and mercury slowly passes out of the cup 39 through the hole 45 till the surface reaches an insulating sleeve 36 and the circuit between electrodes 32, 33 is broken. On de-energization of the magnet 26 the displacer 46 moves back and causes mercury to rise outside the cup 39 and flow over the slanting upper edge of the cup thus causing a quick " make." By using a smaller quantity of mercury, mercury could only enter the cup through the hole 45 and thus there would be a slow " make " as well as a slow " break." In a modification, Figs. 8, 9 (not shown), energization of the magnet lowers the displacer and so causes the " make" while de-energization causes the " break." In another modification, Fig. 11, a slow make of say 6 secs. is produced by the mercury entering the hole 45 in the manner described above, the gas escaping from inside the cup through a porous plug 62 and mercury trap 64. 'A very slow break of say three minutes is produced by the gas being able to gain re-admittance to the cup only through a dense porous sleeve 63 and the plug 62 and thus preventing the mercury escaping through the hole 45 at the rate it would otherwise do. The gas used to fill the switch envelope may include hydrogen and helium.