• Peter Barnes’s explanation of why underfilm corrosion lines do not meet should have read: “The potential at the head of a filament would be neutralised were it to encounter the tail of a different filament, so the only way it can propagate is to change direction” (The Last Word, 3 December).
• We accidentally referred to a “stellar sea lion” (29 November, p 6). The featured mammal is a Steller’s sea lion.
