reversing order of long archive

I have an archive of about 500 messages that were written in the default
mode of oldest first, newest last. I know how to reverse this for future
messages, but I am wondering if there is a way to do a batch reverse on
this archive to put the newest ones first?

Christopher Adams
Automated Systems
Oregon State Library
chris(_at_)sparkie(_dot_)osl(_dot_)state(_dot_)or(_dot_)us