Q: Thunderbolt-Can you use an  adaptor From a thunderbolt External drive to a firewire 800/400 Mac

Yes

No. The Thunderbolt to Firewire adapters only work to connect a Firewire drive to a Thunderbolt port. They do not work in reverse, to connect a Thunderbolt-only drive to a Firewire port. If the only port your drive has is a Thunderbolt port and all you have on the Mac is Firewire, you can't use that drive with that computer.

Regards.

Whoops. It seems I misread the direction of that connection.

I should have waiting until I had my coffee before I answeded that one. Sorry.

Allan

It's easy enough to do. I have to read a post three or four times in this sort of scenario to make sure I really do understand correctly, and even then I goof it up some times. Cheers.