From Montesquieu’s Spirit of the Laws, Book XIV:
Cold air constringes the extremities of the external fibres of the body; this increases their elasticity, and favours the return of the blood from the extreme parts to the heart. It contracts those very fibres; consequently it increases also their force. On the contrary, warm air relaxes and lengthens the extremes of the fibres; of course it diminishes their force and elasticity.
People are therefore more vigorous in cold climates. Here the action of the heart and the reaction of the extremities of the fibres are better performed, the temperature of the humours is greater, the blood moves more freely towards the heart, and reciprocally the heart has more power. This superiority of strength must produce various effects; for instance, a greater boldness, that is, more courage; a greater sense of superiority, that is, less desire of revenge; a greater opinion of security, that is, more frankness, less suspicion, policy, and cunning. In short, this must be productive of very different tempers. Put a man into a close, warm place, and for the reasons above given he will feel a great faintness. If under this circumstance you propose a bold enterprise to him, I believe you will find him very little disposed towards it; his present weakness will throw him into despondency; he will be afraid of everything, being in a state of total incapacity.
(Hat tip: David Touby)
POST-SCRIPT: So there is no confusion, this was not posted as an endorsement, but rather as something of interest. I find this to be particularly interesting as it was raised at a conference examining human adaptation to climate change at which papers were presented examining, among other things, how populations and industries respond to changes in temperature. In this context, it was interesting and a bit amusing to read Montesquieu’s thoughts on the subject. I don’t subscribe to Montesquieu’s analysis, and I certainly would not endorse Montesquieu’s efforts elsewhere in Spirit of the Laws to connect climate with race.