EFFECTS OF VARIATIONS IN MANGANESE. 239 M- Measuring face plate table. FIG. 54.face, a wedge T passed along until it was stoppd by a pin, as at U. The distance the wedge passed under the pin U was measured by a micrometer at V, Fig. 55. The depth of such holes could also be measured by filling them with water and measuring it with a small graduate, shown at W, Fig. 55. The structure, column No. 8, is given merely to denote distinctions as made by the eye in judging the relative size of the crystals or grain of the fracture. For example, No. 2 stands for what would be expected of the grain in a piece of true No. 2 iron, and so on up with closer iron in the higher numbers.