Note 27 — MESSIAH,

The sense and language show, that by "visual ray," the poet meant the sight, or, as Milton calls it, indeed, something less boldly, "the visual nerve." And no critic would quarrel with the figure which calls the instrument of vision by the name of the cause. But though the term be just, nay noble, and even sublime, yet the expression of "thick films" is faulty, and he fell into it by a common neglect of the following rule of good writing, that when a figurative word is used, whatsoever is predicated of it ought not only to agree in terms to the thing to which the figure is applied, but likewise to that from which the figure is taken. "Thick films" agree only with the thing to which it is applied, namely, to the sight or eye; and not to that from which it is taken, namely, a ray of light coming to the eye. He should have said "thick clouds," which would have agreed with both. But these inaccuracies are not to be found in his later poems.—Warburton.

Concanen had previously made the same objection in his Supplement to the Profound, and Pope has written in the margin, "Milton," who uses "visual ray," Par. Lost, iii. 620, "visual nerve" xi. 415, and "visual beam," Samson Agonistes, ver. 163; but none of these passages support Pope's misapplication of the phrase "thick films" to rays of light.