Experts say they have confirmed for the first time the precise origin of some of the rocks at Stonehenge.It has long been suspected that rhyolites from the northern Preseli Hills helped build the monument. But research by National Museum Wales and Leicester University has identified their source to within 70m (230ft) of Craig Rhos-y-felin, near Pont Saeson. The museum's Dr Richard Bevins said the find would help experts work out how the stones were moved to Wiltshire. For nine months Dr Bevins, keeper of geology at National Museum Wales, and Dr Rob Ixer of Leicester University collected and identified samples...