A cause of the French Revolution I never heard of before: The gabelle, a salt tax: it is in my cictionary.

France has always been a
major producer of salt and any discussion of saltmaking in France includes discussion of the gabelle, the
salt tax which was a significant cause of the French Revolution ( 1 2 ), but salt remains important
today. The magnitude of the gabelle is mind-boggling; from 1630 to 1710, the tax increased tenfold
from 14 times the cost of production to 140 times the cost of production, according to Pierre Laszlo in
his book Salt: Grain of Life (Columbia Univ. Press).