Abstract: A mercury tilt switch is provided with electrodes which during operation are oriented in a vertical plane projecting through an end wall of an elongated insulating envelope. The lower electrode is longer than the other and terminated with a blunt end of area of such size and shape as to provide resistance to the surrounding movement of the mercury pool past the end and the subsequently reduced steps of the electrode. When the switch is tilted to close the contacts, the blunt end opposes the mercury pool until the switch is sufficiently tilted that the weight component of the mercury in direction opposed to the blunt end is sufficient to overcome surface tension of the mercury pool, at which point the mercury pool will flow down along the stepped electrode and into contact with the other electrode closing the switch.