large arc, say of 40°, the luminous streak darts away in the opposite
direction. In the latter case, moreover, a faint streak of light
appears later, lying in the direction of the eye-movement.

This phenomenon was probably first described by Mach, in 1886.[8] His
view is essentially as follows: It is clear that in whatever direction
the eye moves, away from its luminous fixation point, the streak
described on the retina by the luminous image will lie on the same
part of the retina as it would have lain on had the eye remained at
rest but the object moved in the opposite direction. Thus, if the eye
moves to the right, we should expect the streak to appear to dart to
the left. If, however, the streak has not faded by the time the eye
has come to rest on a new fixation point (by supposition to the right
of the old), we should expect the streak to be localized to the left
of this, that is, to the right of the former fixation-point. In order
to be projected, a retinal image has to be localized with reference to
some point, generally the fixation-point of the eyes; and it is
therefore clear that when two such fixation-points are involved, the
localization will be ambiguous if for any reason the central apparatus
does not clearly determine which shall be the point of reference. With
regard to the oppositely moving streak Mach says:[9] "The streak is,
of course, an after-image, which comes to consciousness only on, or
shortly before, the completion of the eye-movement, nevertheless with
positional values which correspond, remarkably enough, not to the
later but to the earlier position and innervation of the eyes." Mach
does not further attempt to explain the phenomenon.

[8] Mach, Ernst, 'Beiträge zur Analyze der Empfindungen,' Jena,
1886.