My feet in cold water every morning

This is from my letter to James Maury, June 16, 1815:

I have for fifty years bathed my feet in cold water every morning, and having been remarkably exempted from colds (not having had one in every seven years of my life on an average), I have supposed it might be ascribed to that practice. When we see two facts accompanying one another for a long time, we are apt to suppose them related as cause and effect.