'The absolute accuracy of the Talbot-Plateau law was questioned by Fick [note: 'Reichert's Archiv, p. 739. 1863.'] in 1863, who adopted the same method of investigation as Plateau [note: 'Pogg. Annalen, XXXV. p. 457. 1835.'] had devised some years earlier.' (438)

'Fick [note: 'loc. cit.'] found that the luminosities of the rotating disc measured in this manner did not agree absolutely with that determined by the angle of black upon the disc.

[includes table of data from Fick]

All except the last disc were found to produce a sensation of greater luminosity than would have been expected from calculation of their angular brightness.' (439)

'Schenk [note: 'Pflüger's Archiv, LXVIII. p. 32. 1897.'] has recognised and termed "Flackern" and "Flimmern," corresponding to ordinary or "coarse flicker " and "fine flicker" or molecular movement respectively.' This experimenter has made observations on discs similar to those designed by Sherrington [note: 'This Journal, xxi. p. 37. 1897.']  to show areal induction, and concludes that if the ring-bands be observed separately and closely, disappearance of fine flicker occurs in both at the same speed of rotation. Bearing this in mind I have repeated observations upon the original discs and can but confirm Sherrington's results: that if the physiological difference of two visual stimuli be increased by simultaneous contrast, a greater frequency of alternation is required to produce their fusion, that if the physiological difference of the same too physical stimuli be decreased by the same method. By fusion I mean disappearance not only of coarse flicker but fine flicker as well.

It must be noted that if the ring-bands be examined separately and the eye be placed very close, little if any of the background will be seen, and thus the effect of simultaneous contrast may be greatly diiminished or even absolutely eliminated.' (449-450)

'Some months [note: 'This Jourmal, xxi. p. 396. 1897.'] ago the effect of simultaneous contrast upon the frequency of alternation necessary to fuse moderate stimuli was investigated by me, the method adopted consisted in altering the ratio of the time that the eye was exposed completely to light or darkness and the transition period.

In that paper two kinds of flicker were distinguished, which more recently Schenk [note: Pflüger's Archiv, LXVIII. p. 32. 1897.'] has recognised and termed "Flackern" and "Flimmern," corresponding to ordinary or "coarse flicker " and "fine flicker" or molecular movement respectively.' (449)

'The absolute accuracy of the Talbot-Plateau law was questioned by Fick [note: 'Reichert's Archiv, p. 739. 1863.'] in 1863, who adopted the same method of investigation as Plateau [note: 'Pogg. Annalen, XXXV. p. 457. 1835.'] had devised some years earlier.' (438)

'On increasing the intensity of intermittent stimuli a rapid increase in frequency is necessary at first to produce fusion; after a certain frequency has been attained a further increase in intensity does not necessitate a further increase in frequency, this has been shown by Bellarminow [note: 'Archiv f. Ophthalmolgie, XXV. p. 25. 1889.'] and surmised by Haycraft [note: 'This Journal, XXI. p. 139. 1897.']: but on still further increasing the intensity of the stimuli fusion occurs with a decreased frequency.' (435)

'Marbe [note: 'Wundt Philosoph. Stud. XII. p. 279. 1896 and IX. p. 384. 1893.'] has stated several theoretical reasons for considering the Talbot-Plateau law inaccurate but has not made any direct observations.' (439)

'Marbe [note: 'Wundt Philosoph. Stud. XII. p. 279. 1896 and IX. p. 384. 1893.'] has stated several theoretical reasons for considering the Talbot-Plateau law inaccurate but has not made any direct observations.' (439)

'On increasing the intensity of intermittent stimuli a rapid increase in frequency is necessary at first to produce fusion; after a certain frequency has been attained a further increase in intensity does not necessitate a further increase in frequency, this has been shown by Bellarminow [note: 'Archiv f. Ophthalmolgie, XXV. p. 25. 1889.'] and surmised by Haycraft [note: 'This Journal, XXI. p. 139. 1897.']: but on still further increasing the intensity of the stimuli fusion occurs with a decreased frequency.' (435)

'Two main theories have been suggested to explain the fact that intermittent retinal stimuli repeated above a certain frequency give rise to a steady sensation.

The older, which I shall in future style the "persistence theory," seems to have been suggested by d'Arcy

'Two main theories have been suggested to explain the fact that intermittent retinal stimuli repeated above a certain frequency give rise to a steady sensation.

The older, which I shall in future style the "persistence theory," seems to have been suggested by d'Arcy [note: 'Mem. Akd. Sci. p. 439. 1765.'] in 1765 and maintains that a steady sensation results from intermittent stimuli, when the intervening periods do not exceed the time of duration of the positive after-image of undiminished brightness: in fact, attempts were made by this observer to determine this quantity by noting the minimum freouency with which a burning coal must be rotated in order to produce a sensation of a ring of fire: 0.133 secs. was his estimation.

All subsequent writers, Plateau, Talbot, Helmholtz, etc. adopt d'Arcy's view, Fick [note: Hernann's Handbuch, III. p. 215. 1879.'] being the first to suggest an alternative. This author accepted Exner's [note: Sitzungsberichte Akad. Wein. LVIII. p. 601. 1868, and Pflüger's Archiv, III. p. 240. 1870.'] conclusion, that if the eye be exposed to black after having been stimulated by light, there is at first a rapid fall in the brightiness of the positive after-image, which then more gradually disappears; the curve representing the decrease and disappearance being of exactly a similar nature to that representing the growth of sensation produced by a white stimulus.

Fick diagrammatically represented the sensation resulting from intermittent stimulus by a serrated line, the abscissa being the timerelation and the ordinates the strength of sensation, and pointed out that if the frequency become great, the amplitude of oscillation of sensation diminishes until a frequency is reached at which a continuous smooth sensation results.

It is surprising that writers after Fick's explanation did not adopt his view, since even if Exner's statement that under normal conditions the duration of the after-image of undiminished brightness is infinitely short, be disallowed, nevertheless the persistence-theory seems unsatisfactory' (443-444)

'Towards the end of Part I. [note: 'This Journal, XXI. p. 396. 1897'], a somewhat unexpected result of observations with intense stimuli was stated; in Section I. of this paper the experiments upon which that result was based will be given.' (433)

'The apparatus used for the above work lent itself excellently for repetition of the experiments published in Pt. I., for if the fine flicker seen were due to any other cause than intermittent illumination of the field, such as vibration etc., or was a purely subjective phenomenon [note: 'Burch. Proc. Physiol. Soc. p. xxxvi. 1897. (This Journal, XXI.)']  the half of the field illuminated continuously should have presented a similar appearance when its intensity was equal to the other half. This was not found to be the case and the results confirmed those already published.' (443)

'Some months [note: 'This Jourmal, xxi. p. 396. 1897.'] ago the effect of simultaneous contrast upon the frequency of alternation necessary to fuse moderate stimuli was investigated by me, the method adopted consisted in altering the ratio of the time that the eye was exposed completely to light or darkness and the transition period.

In that paper two kinds of flicker were distinguished, which more recently Schenk [note: ;Pflüger's Archiv, LXVIII. p. 32. 1897.'] has recognised and termed "Flackern" and "Flimmern," corresponding to ordinary or "coarse flicker " and "fine flicker" or molecular movement respectively.' (449)

'Two main theories have been suggested to explain the fact that intermittent retinal stimuli repeated above a certain frequency give rise to a steady sensation.

The older, which I shall in future style the "persistence theory," seems to have been suggested by d'Arcy [note: 'Mem. Akd. Sci. p. 439. 1765.'] in 1765 and maintains that a steady sensation results from intermittent stimuli, when the intervening periods do not exceed the time of duration of the positive after-image of undiminished brightness: in fact, attempts were made by this observer to determine this quantity by noting the minimum freouency with which a burning coal must be rotated in order to produce a sensation of a ring of fire: 0.133 secs. was his estimation.

All subsequent writers, Plateau, Talbot, Helmholtz, etc. adopt d'Arcy's view, Fick [note: Hernann's Handbuch, III. p. 215. 1879.'] being the first to suggest an alternative.' (443-444)

'Two main theories have been suggested to explain the fact that intermittent retinal stimuli repeated above a certain frequency give rise to a steady sensation.

The older, which I shall in future style the "persistence theory," seems to have been suggested by d'Arcy 

'Two main theories have been suggested to explain the fact that intermittent retinal stimuli repeated above a certain frequency give rise to a steady sensation.

The older, which I shall in future style the "persistence theory," seems to have been suggested by d'Arcy [note: 'Mem. Akd. Sci. p. 439. 1765.'] in 1765 and maintains that a steady sensation results from intermittent stimuli, when the intervening periods do not exceed the time of duration of the positive after-image of undiminished brightness: in fact, attempts were made by this observer to determine this quantity by noting the minimum freouency with which a burning coal must be rotated in order to produce a sensation of a ring of fire: 0.133 secs. was his estimation.

All subsequent writers, Plateau, Talbot, Helmholtz, etc. adopt d'Arcy's view, Fick [note: Hernann's Handbuch, III. p. 215. 1879.'] being the first to suggest an alternative. This author accepted Exner's [note: Sitzungsberichte Akad. Wein. LVIII. p. 601. 1868, and Pflüger's Archiv, III. p. 240. 1870.'] conclusion, that if the eye be exposed to black after having been stimulated by light, there is at first a rapid fall in the brightiness of the positive after-image, which then more gradually disappears; the curve representing the decrease and disappearance being of exactly a similar nature to that representing the growth of sensation produced by a white stimulus.

Fick diagrammatically represented the sensation resulting from intermittent stimulus by a serrated line, the abscissa being the timerelation and the ordinates the strength of sensation, and pointed out that if the frequency become great, the amplitude of oscillation of sensation diminishes until a frequency is reached at which a continuous smooth sensation results.

It is surprising that writers after Fick's explanation did not adopt his view, since even if Exner's statement that under normal conditions the duration of the after-image of undiminished brightness is infinitely short, be disallowed, nevertheless the persistence-theory seems unsatisfactory' (443-444)

 in 1765 and maintains that a steady sensation results from intermittent stimuli, when the intervening periods do not exceed the time of duration of the positive after-image of undiminished brightness: in fact, attempts were made by this observer to determine this quantity by noting the minimum freouency with which a burning coal must be rotated in order to produce a sensation of a ring of fire: 0.133 secs. was his estimation.

All subsequent writers, Plateau, Talbot, Helmholtz, etc. adopt d'Arcy's view, Fick [note: Hernann's Handbuch, III. p. 215. 1879.'] being the first to suggest an alternative. This author accepted Exner's [note: Sitzungsberichte Akad. Wein. LVIII. p. 601. 1868, and Pflüger's Archiv, III. p. 240. 1870.'] conclusion, that if the eye be exposed to black after having been stimulated by light, there is at first a rapid fall in the brightiness of the positive after-image, which then more gradually disappears; the curve representing the decrease and disappearance being of exactly a similar nature to that representing the growth of sensation produced by a white stimulus.

Fick diagrammatically represented the sensation resulting from intermittent stimulus by a serrated line, the abscissa being the timerelation and the ordinates the strength of sensation, and pointed out that if the frequency become great, the amplitude of oscillation of sensation diminishes until a frequency is reached at which a continuous smooth sensation results.

It is surprising that writers after Fick's explanation did not adopt his view, since even if Exner's statement that under normal conditions the duration of the after-image of undiminished brightness is infinitely short, be disallowed, nevertheless the persistence-theory seems unsatisfactory' (443-444)

'Two main theories have been suggested to explain the fact that intermittent retinal stimuli repeated above a certain frequency give rise to a steady sensation.

The older, which I shall in future style the "persistence theory," seems to have been suggested by d'Arcy [note: 'Mem. Akd. Sci. p. 439. 1765.'] in 1765 and maintains that a steady sensation results from intermittent stimuli, when the intervening periods do not exceed the time of duration of the positive after-image of undiminished brightness: in fact, attempts were made by this observer to determine this quantity by noting the minimum freouency with which a burning coal must be rotated in order to produce a sensation of a ring of fire: 0.133 secs. was his estimation.

All subsequent writers, Plateau, Talbot, Helmholtz, etc. adopt d'Arcy's view, Fick [note: Hernann's Handbuch, III. p. 215. 1879.'] being the first to suggest an alternative. This author accepted Exner's [note: Sitzungsberichte Akad. Wein. LVIII. p. 601. 1868, and Pflüger's Archiv, III. p. 240. 1870.'] conclusion, that if the eye be exposed to black after having been stimulated by light, there is at first a rapid fall in the brightiness of the positive after-image, which then more gradually disappears; the curve representing the decrease and disappearance being of exactly a similar nature to that representing the growth of sensation produced by a white stimulus.

Fick diagrammatically represented the sensation resulting from intermittent stimulus by a serrated line, the abscissa being the timerelation and the ordinates the strength of sensation, and pointed out that if the frequency become great, the amplitude of oscillation of sensation diminishes until a frequency is reached at which a continuous smooth sensation results.

It is surprising that writers after Fick's explanation did not adopt his view, since even if Exner's statement that under normal conditions the duration of the after-image of undiminished brightness is infinitely short, be disallowed, nevertheless the persistence-theory seems unsatisfactory' (443-444)

'Nor was Sherrington the only British physiologist to experiment with illusions of temporal continuity at this time. Shortly after Sherrington's initial flicker study came out, his Cambridge compatriot Otto Fritz Frankeau Grünbaum published two papers in the Journal of Physiology. [note: 'O.F.F. Grünbaum, 'On Intermittent Stimulation of the Retina (Parts I. and II.)', Journal of Physiology 21 (4-5) (1897), pp. 396-402 and 22 (6) (1898), pp. 433-450.'] These studies, which also addressed the rate at which alternating stimuli fused into continuous perception, strove for far greater precision than had Sherrington. Rather than direct both eyes to an external stimulus in the shape of a rotating disc, Grünbaum created a mechanism (fig. 3) that could project two separate beams of light onto the retina of a single eye. One of these beams was constant, thus constituting a point of comparison. The other beam however was interrupted by a rotating disc with angular segments cut out of it. By rotating this disc at different speeds, Grünbaum sought to arrive at a more accurate estimation of the rates of exposure necessary for the experiences of different brightnesses. The parallels between the establishment of illusion-generating devices within physiology laboratories and that of cinematographic technology more generally are prominent here. One of the key elements of the cinematograph - and one of the most difficult pieces to co-ordinate with the movement of celluloid film-strips - was a disc or 'shutter' (similar to the ones Talbot and von Stampfer had developed) that cut off the projection of light at intervals proportional to the replacement of images on the projector. The minimal rate at which cinematographic images had to be replaced and exposed to view was determined by the rate at which images could be perceived as individual, rather than a continuous moving picture - i.e. by the phenomena of persistence of vision. [note: 'Münsterberg made the connection explicit. See H. Münsterberg, The Photoplay: a Psychological Study (New York and London: D. Appleton, 1916), pp. 57-71.'] During the 1890s, the physiological study of flicker fusion and the construction of cinematographic devices went hand in hand.'