... mines, timed to go off at any time up to twenty-eight days. One could never be sure that the ground underneath one's feet would not blow up at any moment. These mines were small boxes of high explosive, inside of which was a little metal tube with trigger and detonator attached. Inside the tube was a powerful acid, which, when it had eaten its way through, set free the trigger and exploded the charge. The length of time it took for the mine to explode was gauged by the strength or weakness of the ... — Life in a Tank • Richard Haigh
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