Tea leaves is the answer to this one. Unless a tea strainer was used (only when we had guests) tea leaves would settle at the bottom of the cup. If you inadvertently got a mouthful you would immediately spit them out. This is one of the solutions to the age-old conundrum - which first, tea or milk? The answer was always milk, because the tea leaves would gravitate to the bottom of the cup. Put the milk in afterwards and the leaves wouldn't settle. There are other explanaitons given, such as the protection of fine bone china cups, but I don't want to ignite another debate. As leaf tea is so rare these days the question is largely irrelevant.