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.)



Measurement of the Distance between the Mirrors.


Square lead weights were placed along the line, and measurements taken
from the forward side of one to forward side of the next. The tape rested
on the ground (which was very nearly level), and was stretched by a
constant force of 10 pounds.

The correction for length of the tape (100.006) was +0.12 of a foot.