Posted by e-shark on September 07, 2001 at 20:16:29:
In Reply to: Re: How many feet p/min. posted by Capt-Ray on September 07, 2001 at 20:00:17:
It's one of those rules of thumb that have an amazing persistence, even though no one ever seems able to say exactly how they "know" the smallest bubbles rise at 60 fpm or less.