Note 87 — Chapter IV

This is about double the true figure, 13 geographical miles. I made a practice of asking each member of the expedition his estimate of every march, registered the lowest, and found on comparing it with actual measurement by the cord that it was usually twice too long. When instruments are not used this must ever be expected. But it is no objection to the general credibility of a book if its 300 miles of distance are reduced to 120. This sounds like a truism: apparently, however, it is not generally acknowledged to be true.