Deep cuttings and long tunnels are regarded by railway-contractors as things to be avoided, though lessons of the greatest instruction are derived from them by the student of geology. But as safety in transit demands the easiest gradients, and a line as straight as possible, the lesser inequalities of the surface have often to be cut into, so that no insignificant part of geological teaching is derived from railway-work. And oft-times a way that puzzles the contractor to make “ good,” or a hill-slope that, lacking Knowledge of its springs, he has cut into only to see it slip continuously upon his line, are great aids and helps to comprehending the natural formation of a district, and so, a contractor's poison becomes a geologist's meat.