Corrections: Incorrect units appeared in a Technology story 鈥淭ough bones are sound as a bell鈥� on 26 August. The audible range is between 100 and 1000 hertz, not megahertz as stated.
Also, in 鈥淒eath and the devil鈥檚 water鈥� (Focus, 16 September), all references to the amounts of arsenic in the water were incorrectly given as milligrams per litre, rather than micrograms per litre. We apologise for these unfortunate errors.
