law: Indian Ports Act, 1908
  46. Port-due on vessels in ballast 
  A vessel entering any port 14[not being a major port]
  
  subject to this Act 19[***] in ballast and not carrying passengers
  
  shall be charged with a port-due at a rate to be determined by the 58[Government]
  
  and not exceeding three-fourths of the rate with which she would otherwise be
  
  chargeable.