[X4U] Why does Safari use so much memory?

[B.ru c-e •K1u-tch-k0]

I've been watching the memory use of Safari as I continue to browse.  
It starts off at a modes few MB, but after an hour or so of visiting  
several sites I find that it uses 60, 70, or sometimes even 100 MB of  
real memory and hundreds of MB of virtual memory.

Emptying the cache seems to have no effect, and emptying the Webcore  
and Webfoundation caches on the debug menu seems to have only a  
modest effect.

Are these numbers typical? Is there something I should do to prevent  
Safari from seeming to gobble up an ever increasing amount of memory?  
Relaunching helps, but I'm wondering if there is a better way short  
of quitting the program.

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B-r-u -c-e