9So moreover, from the clearness of the atmosphere, aided also by the intense heat, the southern nations are more ready and quick in expedients: but the northern nations, oppressed by a gross atmosphere, and cooled by the moisture of the air, are of duller intellect. That this is so, may be proved from the nature of serpents, which in the hot season, when the cold is dispelled by the heat, move with great activity, but in the rainy and winter seasons, from the coldness of the air, they become torpid. Hence it is not surprising that man’s intellect should be sharpened by heat and blunted by a cold atmosphere.
9Further, it is owing to the rarity of the atmosphere that southern nations, with their keen intelligence due to the heat, are very free and swift in the devising of schemes, while northern nations, being enveloped in a dense atmosphere, and chilled by moisture from the obstructing air, have but a sluggish intelligence. That this is so, we may see from the case of snakes. Their movements are most active in hot weather, when they have got rid of the chill due to moisture, whereas at the winter solstice, and in winter weather, they are chilled by the change of temperature, and rendered torpid and motionless. It is therefore no wonder that man’s intelligence is made keener by warm air and duller by cold.