23 feet down, 13.10 feet east, and 3.43 feet north. You see
I am exact. I have to be. In one minute it moved 0.080 feet upward,
0.053 feet to the right, and 0.096 feet in its apparent path. It
passes the width of a weatherboard, 0.37 foot, in four minutes and
thirty-seven seconds."
Kennedy was talking rapidly of data which he had derived from his
metric photograph, from plumb line, level, compass, and tape,
astronomical triangle, vertices, zenith, pole and sun, declination,
azimuth, solar time, parallactic angles, refraction, and a dozen
bewildering terms.
"In spherical trigonometry," he concluded, "to solve the problem
three elements must be known. I knew four. Therefore I could take
each of the known, treat it as unknown, and have four ways to check
my result. I find that the time might have been either three
o'clock, twenty-one minutes and twelve seconds, in the afternoon, or
3:21 :31, or 3 :21 :29, or 3:21 :33. The average is 3 :21 :26, and
there can therefore be no appreciable error except for a few seconds.
For that date must have been one of two days, either May 22 or
July 22. Between these two dates we must decide on evidence other
than the shadow. It must have been in May, as the immature condition
of the foliage shows.
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