Preparation of Diagram

CHAPTER VII.

Quantities of Materials (Cont'd).

II. Volumes from Original Contours.

4. Displacement Diagrams.

Preparation of Diagram.

As a requisite in this form of measurement an accurate displacement diagram of the given vessel or scow must be made, being carefully plotted to some suitable scale. To prepare this displacement diagram, the vertical distance or depth that the vessel or scow sinks when loaded, as compared with its depth when empty, is first found and then accurately divided into any number of equal parts.

The wetted perimeter of the vessel at each one of these equidistant parts must then be measured and accurately plotted to a suitable scale, each such area being superimposed on the others on the diagram. In the case of a scow, which is usually rectangular in plan, these displacement areas can be found by actual measurement, while in the case of a curved or shaped vessel they are more easily obtained from the builder's plans.

It will be readily seen that these displacements or wetted areas are exactly the same as obtained in our previous illustrations by the passing of equidistant, parallel, horizontal planes through the mass of material to be measured, and that the entire operation is exactly the same as already described in the previous cases referred to. It is also evident that the method of measuring the volume of water displaced is identical with the method of measurement employed in the previous examples.

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