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device for selbsttaetigen ads of firedamp by a gas gefuellten balloon, under the influence of grubengasen his position by means of a pointer, which modifies and, at the same time, percentage of displays
device for selbsttaetigen ads of firedamp by a gas gefuellten balloon, under the influence of grubengasen his position by means of a pointer, which modifies and, at the same time, percentage of displays
