Reykjavik - A cloud of ash from Iceland's Mount Hekla volcano drifted towards Ireland and Britain yesterday, but geologists said the eruption was subsiding. The volcano has been erupting from two craters, but a geophysicist at Iceland's Meteorological Office said that one of these had shut down early yesterday. Metereologists said the ash was drifting southeast over the Atlantic Ocean towards Britain but was unlikely to cause problems as the eruption had weakened.