XXXIII. WHAT IS THE REASON THAT PIT-WATER IS LESS NUTRITIVE THAN EITHER THAT WHICH ARISETH OUT OF SPRINGS OR THAT WHICH FALLETH DOWN FROM HEAVEN? Is it because it is more cold, and withal hath less air in it? Or because it containeth much salt from the earth mingled therewith?—now it is well known that salt above all other things causeth leanness. Or because standing still, and not exercised with running and stirring, it getteth a certain malignant quality, which is hurtful to both plants and animals, and is the cause that it is neither well concocted nor able to feed and nourish any thing? Hence it is that all dead waters of pools are unwholesome, for that they cannot digest and despatch those harmful qualities which they borrow of the evil property of the air or of the earth.