About the stereoscopic phenomena and Wheatstone's attack on the theory of the identical points of the retinas: Part 2.

In Plate XVII, Figure 4, let AB be the distance of the crossing points of the visual rays in both eyes, which Wheatstone assumes to be 2.5 inches, and half of that (AC) is 1.25 inches. Wheatstone uses this experiment to show that images can not only appear single on non-identical points on the retina, but images can also appear twice on identical points. 1.25: 7 = r: tang CAEAccordingly:tang CAE I = i 28/5 I and i :log tang CAE = log 28 - log 5log 28 = 1.4471580log 5 = 0.9689700log tang CAE = 0.4781880angle CAE = 79° 52'Similarly:1.25: 9 = r: tang CAD,And:tang CAD = 36/5,and log tang CAD = log 36 - log 5.log 36 = 1.5563023log 5 = 5.6989700log tang CAD = 5,8573325angle CAD = 82° 5'angle CAE = 79° 52'angle CAD - angle CAE = angle DAE = 2° 13' That such a movement of our eyes would escape our attention cannot be considered a wonder and, in fact, it escapes our attention every moment we look at the physical external world, as has been shown above. From these general objections I [as discussed in the first part of the translation] i I proceed to the experiments which Wheatstone[1] adduces as evidence against the basic idea of this theory I [that the visual impression of an object is not single and not absolutely instantaneous but rather the aggregate of many impressions that come to the sense one after the other] i , noting that, until now, he has only drawn negative conclusions from them and I therefore will have completed my task if I confirm that his experiments offer no valid proof against the above theory. [Extracted from the article]