Item 8 - Letter from John Herschel

WW should submit his paper to the Royal Society ['A General Method of Calculating the Angles Made by Any Planes of Crystals, and the Laws According to which They are Formed', Phil. Trans., 1825]: 'Your idea of denoting every possible secondary face by one symbol (p, q, r) where p, q, r may be either + or - is excellent'. Although JH had adopted 'decrements on edges as partcular cases of decrements on angles' he 'did not think of negative decrements, which give your method its generality'.