law: Transfer of Property Act, 1882
  23. Transfer contingent on happening of specified
  
  uncertain event
  Where, on a transfer of property, an interest therein is to
  
  accrue to a specified person if a specified uncertain event shall happen, and
  
  no time is mentioned for the occurrence of that event, the interest fails
  
  unless such event happens before, or at the same time as, the intermediate or
  
  precedent interest ceases to exist.