The United States Standard Of Length. "The standard yard of Great Britain was lawful in the colonies before 1776. By the Constitution of the United States the Congress is charged with fixing the standard of weights and measures, but no such enactment has ever been made by Congress, and therefore that yard which was standard in England previous to 1776 remains the standard yard of the United States to this day."1

1 Shelley's "Workshop Appliances."

2 Report of the United States Coast Survey, 1877, Appendix No. 12.

17. "The Troughton Scale is a bronze bar with an inlaid silver scale, made for the survey of the coast of the United States by Troughton, of London. The bar is nearly 86 inches long, 2 1/2 inches wide, and one-half inch thick. A thin strip of silver, a little more than 0.1 inch wide, is inlaid with its surface flush with the brass, midway the width of the bar. It extends the whole length of the bar, save where it is interrupted by two perforations, one near each end. Two parallel lines about 0.1 inch apart are ruled longitudinally on the silver. The space between them is divided transversely into tenths of inches.

"The zero mark of the graduations is about 3.2 inches from one end of the bar. Immediately over it is engraved an eagle, surmounted by the motto, E Pluribus Uhum, and thirteen stars. Below the 38 to 42-inch divisions is engraved ' Troughton, London, 1814.' The bar is also perforated by a hole above the scale and near the 40-inch division, and by one below it, between the words ' Troughton' and ' London.' . . .

"The yard of 36 inches, comprised between the 27th and 63d inch of the Troughton scale, which was found by Hassler's comparison to be equal to the average 36 inches of the scale, is the actual standard yard of the United States, having been adopted by the Treasury Department as such in 1832, on the recommendation of Mr. Hassler.2"1

18. Rules are measuring strips, and are usually made of boxwood. Their size is expressed by their length in inches or feet, as a "6-inch rule," a "2-foot rule."

For convenience, they are made to fold, and one is said to be "two-fold" when made of two pieces, "four-fold" when made of four, and "six-fold" when made of six pieces. Fig. 28 shows a four-fold rule.

Fig. 28

1 Report of the United States Coast Survey, 1877, Appendix No. 12.

2 Hassler was the first superintendent of the United States Coast Survey.

To preserve the rule from wear, the better class are "bound" by a strip of brass which covers each edge; others are "half-bound," having only one edge covered; and still others are "unbound," having no edge protection.

Carpenters' rules are usually graduated to eighths of inches on one side, and to sixteenths on the other. Besides the regular graduations, other numbers are frequently represented; but their purpose is so varied that their interpretation cannot be given here.

19. The Framing-Square, Fig. 29, as its name implies, is intended primarily for use in framing, and would seem to belong to the builder rather than to the bench-worker; but its range of usefulness makes it valuable to any worker in wood.

All but the very cheapest are of steel, and many are nickel-plated. The nickel prevents rust, and gives clearness to the lines and figures. The figures of the graduations along the several edges, begin at the angle and extend to the ends of the legs. In addition to these, there is on one side a line of figures beginning at the end of the long leg and extending to the angle. On the reverse side, represented by Fig. 29, there is on the long leg a board-measure table, and on the short leg a brace-measure table.