Postscript.
Reading edition
The comparison of the micrometer with two scales made by Mr. Rogers, of the Harvard Observatory, has been completed. The scales were both on the same piece of silver, marked "Scales No. 25, on silver. Half inch at 58° F., too short .000009 inch. Centimeter at 67° F., too short .00008 cm."
It was found that the ratio .3937079 could be obtained almost exactly, if, instead of the centimeter being too short, it were too long by .00008 cm. at 67°.
On this supposition the following tables were obtained. They represent the value of one turn of the micrometer in millimeters.
Table 1 is the result from centimeter scale.
Table 2 is the result from half-inch scale.
Table 3 is the result from page 31.
It is seen from the correspondence in these results, that the previous work is correct.
(1) (2) (3)
From 0 to 13 .99563 .99562 .99570
25 .99562 .99564 .99571
38 .99560 .99572 .99576
51 .99567 .99578 .99580
64 .99577 .99586 .99585
76 .99582 .99590 .99592
89 .99590 .99598 .99601
102 .99596 .99608 .99605
115 .99606 .99614 .99615
128 .99618 .99622 .99623
140 .99629 .99633 .99630