Experimental Determination of the Velocity of Light / Made at the U.S. Naval Academy, Annapolis - Albert A. Michelson

Changing the form of this table, we find that,—

For the first
10	turns the average value of D′ is	38.155
20	turns	38.153
30	turns	38.152
40	turns	38.151
50	turns	38.149
60	turns	38.148
70	turns	38.146
80	turns	38.144
90	turns	38.142
100	turns	38.140
110	turns	38.138
120	turns	38.135
130	turns	38.132
140	turns	38.130

On comparing the scale with the standard meter, the temperature being 16°.5 C., 140 divisions were found to = 139.462^mm. This multiplied by (1 + .0000188 × 16.5) = 139.505^mm.

One hundred and forty divisions were found to be equal to 140.022 turns of the screw, whence 140 turns of the screw = 139.483^mm, or 1 turn of the screw = 0.996305^mm.

This is the average value of one turn in 140.

But the average value of D, for 140 turns is, from the preceding table, 38.130.

Therefore, the true value of D, is 38.130 × .996305^mm, and the average value of one turn for 10, 20, 30, etc., turns, is found by dividing 38.130 × .996305 by the values of D;, given in the table.

This gives the value of a turn—

			mm.
For the first	10	turns	0.99570
	20	turns	0.99570
	30	turns	0.99573
	40	turns	0.99577
	50	turns	0.99580
	60	turns	0.99583
	70	turns	0.99589
	80	turns	0.99596
	90	turns	0.99601
	100	turns	0.99606
	110	turns	0.99612
	120	turns	0.99618
	130	turns	0.99625
	140	turns	0.99630

Note.—The micrometer has been sent to Professor Mayer, of Hoboken, to test the screw again, and to find its value. The steel tape has been sent to Professor Rogers, of Cambridge, to find its length again. (See page 145.)