4. But we, according to Plato’s opinion, assert that a bright spirit darted from the eye mixes with the light about the object, and those two are perfectly blended into one similar body; now these must be joined in due proportion one to another; for one part ought not wholly to prevail on the other, but both, being proportionally and amicably joined, should agree in one third common power. Now this (whether flux, illuminated spirit, or ray) in old men being very weak, there can be no combination, no mixture with the light about the object; but it must be wholly consumed, unless, by removing the letters from their eyes, they lessen the brightness of the light, so that it comes to the sight not too strong or unmixed, but well proportioned and blended with the other. And this explains that common affection of creatures seeing in the dark; for their eye-sight being weak is overcome and darkened by the splendor of the day; because the little light that flows from their eyes cannot be proportionably mixed with the stronger and more numerous beams; but it is proportionable and sufficient for the feeble splendor of the stars, and so can join with it, and co-operate to move the sense. _QUESTION IX._ WHY FRESH WATER WASHES CLOTHES BETTER THAN SALT. THEON, THEMISTOCLES, METRIUS FLORUS, PLUTARCH, AND OTHERS. 1. Theon the grammarian, when Metrius Florus gave us an entertainment, asked Themistocles the Stoic, why Chrysippus, though he frequently mentioned some strange phenomena in nature (as that salt fish soaked in salt water grows fresher than before, fleeces of wool are more easily separated by a gentle than a quick and violent force, and men that are fasting eat slower than those who took a breakfast), yet never gave any reason for the appearance. And Themistocles replied, that Chrysippus only proposed such things by the by, as instances to correct us, who easily and without any reason assent to what seems likely, and disbelieve every thing that seems unlikely at the first sight. But why, sir, are you concerned at this? For if you are speculative and would enquire into the causes of things, you need not want subjects in your own profession; but pray tell me why Homer makes Nausicaa wash in the river rather than the sea, though it was near, and in all likelihood hotter, clearer, and fitter to wash with than that? 2. And Theon replied: Aristotle hath already given an account for this from the grossness of the sea water; for in this an abundance of rough earthy particles is mixed, and those make it salt; and upon this account swimmers or any other weights sink not so much in sea water as in fresh, for the latter, being thin and weak, yields to every pressure and is easily divided, because it is pure and unmixed; and by reason of this subtility of parts it penetrates better than salt water, and so looseneth from the clothes the sticking particles of the spot. And is not this discourse of Aristotle very probable?