The professional, however, has all his energies directed to make things pay. He has too much at stake to speculate. He chooses the safest way. He is the true conservative, and when he gets hold of anything that works passable well, changes with reluctance. If an amateur experiments with a new toning bath on a batch of perhaps half-a-dozen prints, and fails, well the loss is not great, and he gains in knowledge and experience. But the professional has his batch of perhaps six hundred, and if he fail, the loss is something considerable....