Page:Philosophical Transactions - Volume 013.djvu/185

 3. It is urg'd That according to my Scheme of the situation of the correspondent fibres, the Raies of an object plac't laterally (suppose toward the left Eye) could not fall upon the fellow Fibres in the right Eye; for if it were plac't so slantingly toward the left Eye the raies could not fall upon the internal lateral Fibres of both Eyes in that position; but upon the internal of one, suppose the left Eye, and the external lateral of the right; which would cause a double perception. This Objection I foresaw when I hinted (in p. 176. of the aforesaid Collections) that Whether the Nerves decussated or not, it would be no prejudice to my Opinion, nay perhaps might more fully confirm my opinion where they do. In that passage I had respect also I confess to the inversion of the Image in the Eye being rectified in the Brain; tho that equally presses any other Hypothesis, and the explication of the thing may be well enough understood by a blind man's judging of the position of an object above his head by touching it with one end of his stick, tho the other end terminates under that Object or in his hand: And so in our view of an object the true situation of the respective parts is not distinguish't so much by the means of that end of the ray that terminates in the Eye as of t' other end that touches the Object, from whence the vibration or protrusion comes.

But to leave this which does not so particularly concern me, I come to the objection it self as it relates to my Opinion; and tho it seems at first view the most difficult of all to be answer'd, yet it may be determin'd by the Experiment it self, better than by the Scheme (in the Philos. Collections), where the Eyes are not drawn in that position that is here requir'd. Now let there be plac't an object near the left Eye of any person (but not so near that Eye as that the Nose might hinder the rays from falling on the right, because it is to be seen with both), and whilst that person looks on it let a By-stander observe the position of both Eyes, and he shall see that the pupil of the right Eye is turn'd in a very oblique manner to the object, whereas the pupil of the