light of the Sun doth really dilate it self into so vast a compass, My answer is, That contraction and dilation are natural corporeal actions or motions, and that there is no alteration of motion in Nature, but is done in Time, that is, successively, not instantly; for Time is nothing else but the alteration of motion: Besides, I do not perceive any so sudden and swift alteration and succession of light, but that it is done by degrees: As for example; in the morning, when it begins to dawn and grow light, it appears clearly to our sight how light doth come forth, and darkness remove by degrees; and so at night, when it grows dark, how light removes, and darkness succeeds; nay, if there be any such sudden change of the motions of Light, I desire you to consider, _Madam_, that light is a very subtil, rare, piercing and active body, and therefore its motions are much quicker then those of grosser bodies, and cannot so well be perceived by our gross exterior senses. But if it be, that the Air doth pattern out the light of the Sun, then the framed objection can prove nothing, because there is not then such a real dilation or succession of light, but the corporeal figurative motions of the Air do make patterns of the light of the Sun, and dissolve those patterns or figures again, more suddenly and quickly then man can shut and open his eyes, as being more subtil then his gross exterior senses. But it may be said, that if Air did pattern out the light of the Sun, the light would increase by these numerous patterns. I answer, that cannot appear to our Eyes; for we see onely the pattern'd figure of light, and that a great compass is enlightned; also that the further the air is from the Sun, the darker it is; nevertheless, I do verily believe, that the body of the Sun is far brighter then the light we see, and that the substance of light, and the patterns taken from light, are not one and the same, but very different. And thus much of light. As for Penetration, I conceive it to be nothing else but division; as when some parts pierce and enter through other parts, as Duellers run each other thorow, or as water runs through a sieve. And this is the opinion of, Madam, _Your faithful Friend,_ _and Servant._ [1] _In the Append. to the Antid. c._ 3. and _Of the Immortality of the Soul, l._ 1. _c._ 5. [2] _Sect._ 1. _Let._ 20. XXIV. _MADAM,_