Harper's New Monthly Magazine Volume 104 December 1901 to May 1902 . idual, and with the same eyeat different degrees of fatigue. But it ispractically uninfluenced by the strongestexertion of the will. It may seemstrange that we cannot move our eyesslowly if we choose, but on closer inspec-tion this inability is seen to be a wiseprovision of nature. We could gain nothing by voluntarycontrol of the eye-movements. And if weoccasionally succeeded in moving themslowly, the results would be altogetherunpleasant and misleading. At aboutone-quarter of the ordinary velocity thewhole field of vision wo
Harper's New Monthly Magazine Volume 104 December 1901 to May 1902 . idual, and with the same eyeat different degrees of fatigue. But it ispractically uninfluenced by the strongestexertion of the will. It may seemstrange that we cannot move our eyesslowly if we choose, but on closer inspec-tion this inability is seen to be a wiseprovision of nature. We could gain nothing by voluntarycontrol of the eye-movements. And if weoccasionally succeeded in moving themslowly, the results would be altogetherunpleasant and misleading. At aboutone-quarter of the ordinary velocity thewhole field of vision would fuse into auniform gray during every eye - move-ment. A gray veil would seem to shutout everything from view about fourtimes a second as we read this page. Ifone winks as fast as possible for abouta minute, one gets about the same un-pleasant sensations. If the eyes shouldmove still more slowly, the whole fieldof vision would seem to rush past oneat every eye-movement; and we wouldcontinually be misled by these illusionsof motion. 940 HARPERS MONTHLY Fig. Ill—The broken line atthe left of the figure is reproducedfrom a photographic record of themovements of a point of light onthe eyeball, when the subject triedto move his eyes as rapidly aspossible back and forth betweentwo points. The duration of theactual eye-movement is represent-ed by the vertical height of theoblique lines ; the moments of restby the length of the vertical duration of the eye - move-ments is less than one-tenth of thetotal time. Yet it seemed to thesubject as if his eyes moved con-tinuously. Each division of thescale at the right of the figure cor-responds to one-fifth of a second. If one takes pains to watch the eyes ofa person reading, it will be noticed thateach sweep of the eyes across the pageto the right is broken by a number ofpauses, which may be counted with a lit-tle practice. The frequency of thesepauses is a fairly good measure of thedifficulty of reading. They are fe
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