he wondered , as he always did , which one the live rail was ; and decided , as he always did , that it was the one farthest from the platform , with the large whitish porcelain insulators , between it and the ground ; and then he found himself smiling , involuntarily , at a tiny dark gray mouse who was bravely prowling the tracks , three feet below him , in a mousy , quest for abandoned sandwiches and dropped potato chips .