We see, said he, some species that come from the object to the eye, which at their first rise are thick and great; and therefore when near disturb old men, whose eyes are stiff and not easily penetrated; but when they are separated and diffused into the air, the thick obstructing parts are easily removed, and the subtile remainders coming to the eye gently and easily slide into the pores; and so the disturbance being less, the sight is more vigorous and clear.

Thus a rose smells most fragrant at a distance; but if you bring it near the nose, it is not so pure and delightful; and the reason is this,--many earthy disturbing particles are carried with the smell, and spoil the fragrancy when near, but in a longer passage those are lost, and the pure brisk odor, by reason of its subtility, reaches and acts upon the sense.
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 eyesight 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 cooperate to move the sense.
QUESTION IX.

WHY FRESH WATER WASHES CLOTHES BETTER THAN SALT.
THEON, THEMISTOCLES, METRIUS, FLORUS, PLUTARCH; AND OTHERS.
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 meat 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.