The measurement of r is affected in the same way as D, so that we may
call the greatest error of this measurement .00004. It would probably be
less than this, as the mistakes in the individual measurements would also
appear in the probable error of the result.

The measurement of φ was not corrected for temperature. As the corrections
would be small they may be applied to the final result. For an increase of
1° F. the correction to be applied to the screw for unit length would
be -.0000066. The correction for the brass scale would be +.0000105, or
the whole correction for the micrometer would be +.000004. The correction
for the steel tape used to measure r would be +.0000066. Hence the
correction for tan. φ would be -.000003 t. The average temperature of the
experiments is 75°.6 F. 75.6-62.5 = 13.1. -.000003×13.1 = -.00004

Hence φ should be divided by 1.00004, or the final result should be
multiplied by 1.00004. This would correspond to a correction of +12
kilometers.

The greatest error, excluding the one just mentioned, would probably be
less than .00009 in the measurement of φ.

Summing up the various errors, we find, then, that the total constant
error, in the most unfavorable case, where the errors are all in the same
direction, would be .00015. Adding to this the probable error of the
result, .00002, we have for the limiting value of the error of the final
result ±.00017. This corresponds to an error of ±51 kilometers.

The correction for the velocity of light in vacuo is found by multiplying
the speed in air by the index of refraction of air, at the temperature of
the experiments. The error due to neglecting the barometric height is