http://www.youtube.com/watch?v=RLPVCJjTNgk So it was known since ancient times - but who else knew and how ancient is 'ancient'? Regards Crispin -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.bioenergylists.org/pipermail/stoves_lists.bioenergylists.org/attachments/20101216/9dc236a0/attachment.html>