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CHAPTER VI.

Quantities of Materials.

I. Volumes from Cross Sections.

3. Volumes of Continuous Prismoids.

b. Volumes from Field Notes direct.

Preparing the Templet.

Having decided upon one of the scales commonly used for plotting Cross-sections in railroad and similar work, a sheet of Cross-section paper ruled to the scale chosen is carefully pinned down to the drawing board as shown in the diagram on Plate VI which illustrated this operation. A heavy vertical line near the center of the sheet of Cross-section paper is then selected as a center line and a corresponding heavy horizontal line near the bottom of the sheet is selected as the base of the Cross-sections.

The width of road-bed and ratio of side slopes of the Cross-sections being of course, known, a template is prepared for that particular width of bed and slope ratio as shown on the diagram mentioned.

This template may be of good stiff card or bristol board but what is by far more preferable and accurate is one made of transparent celluloid or “Xylonite” which is manufactured and supplied only by the Keuffel & Esser Co. of New York City and from whom templates of this description for any desired scale and for any width of road-bed or ratio of slope desired can be obtained.

In the diagram mentioned (Plate VI) the scale of the Cross-section paper is 1 inch to 8 feet, while the template shown is cut to that scale and is for a road-bed having a width of thirty-two feet and a slope ratio of 1½ to 1.

A line cut in the template at the center point of and at right angles to the base permits placing the template on the Cross-section sheet, so that the road-bed of that template and its center line will coincide with the horizontal and vertical lines of the Cross-section selected for the base and Center line of the sections.

The template having been thus adjusted to the cross-section sheet it is securely fastened in position by thumb tacks through the template and paper as shown on the diagram.

Having adjusted the Planimeter to the Setting in Table 8 for the scale 1 in. = 8 ft. the Planimeter is placed in the proper position on the Cross-section sheet, the Tracer brought to the point of beginning and the instrument set to a Zero Reading.

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