Note 23 — Chapter XIV · —MEASURING MACHINES, TOOLS, AND DEVICES. (continued 2)

The lengths of circumference were taken, in this and other hoops, after each cooling, by encircling the periphery with a very fine piece of “crinoline” steel, the ends of which were made just to meet round the original hoop. By again encircling the hoop with the same piece of steel the expansion was shown by a gap between the ends, and a contraction by an overlap, either of which was measured with great accuracy by means of a finely divided scale.