Mr. Chardin says there is no navigable river in Persia, unless it be the Kur, which is at the extremities of the empire.  The ancient law of the Ghebers that forbade navigating on rivers therefore had no drawback in their country ; but it would have ruined trade in another.
Continual use is made of lotions in warm climates. For that reason, Mohammedan law and Indian religion prescribe them. It is a very meritorious act in the Indies to pray to God in running water,  but how can these things be performed in other climates ?
When religion based on climate has clashed too greatly with the climate of another country, it has been unable to establish itself there, and when it has been introduced, it has been driven out. It seems, humanly speaking, that it is climate that has prescribed boundaries for the Christian and Mohammedan religions.
It follows from this that it is almost always appropriate for a religion to have local doctrines and a generalized ritual. In the laws that relate to the practices of observance, few details are needed : for example, mortifications and not a certain mortification. Christianity is full of good sense : abstinence is a divine institution, but a particular abstinence is a matter of public policy, and can be changed.