From a known optical illusion derived from interference or fits of
perception, as illustrated in quick moving shadows, this great speed
was not realized to the eye, as the observed motion of these shadows
was apparently far less rapid than their reality.
The ultra or diffraction bands outside of the shadow were distinctly
seen and described by Mr. J.E. Keeler at Central City, both before and
after totality. He estimates the shadow bands at 8 inches wide and 4
feet apart.
Professor E.S. Holden, also at Central City, estimated the dark bands
as about 3 feet apart, and variable.
From estimates which he obtained from other observers of his party,
the distances between the bands varied from 6 to l1/2 feet, but so
quickly did they pass that they baffled all attempts to count even the
number that passed in one second.
He observed the time of continuance of their passage from west to east
as forty-eight seconds, which indicates a width of 33 miles of
diffraction bands stretching outward from the edge of the shadow to
the number of many thousands.
Mr. G.W. Hill, at Denver, a little to the north of the central track
of the shadow, observed the infra or bands within the shadow, alluding
to the fact that they must be moving at the same rate as the shadow,
although their apparent motion was much slower, or like the shadows of
flying clouds. He attributes the discrepancy to optical illusion.
Pages:
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173