Real frequency of meteoritical events of megatonic class.

The author has attempted to determine the real frequency of meteoritical
events of megatonic class through a bibliographic search for events that
occurred during the last two centuries. The outcome of this search was
unexpected: (1) megatonic events seem to occur once every ten years; and
(2) the discovery of some presently unknown events. A list of possible
or certain megatonic events is presented.