There will be an abundant supply of water under the bank at the foot of a mountain, if the bank runs from east to west and not if it runs from north to south. Where there may be streams running along the bank, the bank breaks generally when the waves strike against it. In the absence of such streams water shall be collected by the side of the bank by means of dykes constructed of stones or wood. The water shall then be stirred up by horses, elephants and other animals, the waves dashing against the bank will break it.