The unaided eye part III

Coincidence observations; description of apparatus and safeguards. Coincidence accuracy observations with results. Variables that affect the observations. Distinction between precision and adjustment errors. Variation of precision with length of thick coincidence lines, similar results for thin lines. Minimum precision error relatively to length of coincidence line. Effect on precision of separating line thickness. Adjustment errors. Effect on adjustment of separating line thickness. Variation with length of line. Variation with thickness of line. Effect of premature judgment. Verticalising power of eye. Relation to coincidence adjustment error. Effect of astigmatism on error. Theories of vision. General review of subject. Statement of proposed series theory. The location of images independent of cone diameters. The form apparatus. The colour apparatus. Its explanation of red, green and blue colour blindness, monochromatic threshold vision. Anomalous trichromatic vision. Polychromatic foveal vision. Contrast phenomena. Suggested functions of retinal layers of ganglion cells. Their relation to contrast and irradiation phenomena. Axis cylinder of nerve fibres.