I stand corrected. Thanks for the info, Brent, I've learnt something today, and therefore it must be a good day. Tara -- ______________________________________________________ Tara Deen School of Earth Sciences Division of Geology and Geophysics Building FO5 University of Sydney NSW 2006 Phone: 61-2-9351 4271 Fax: 61-2-9351 0184 email: tara@es.usyd.edu.au ______________________________________________________