Variable. Well up in belladonna, opium, and poisons generally. Knows nothing of practical gardening.
Practical, but limited. Tells at a glance different soils from each other. After walks has shown me splashes upon his trousers, and told me by their colour and consistence in what part of London he had received them.
Accurate, but unsystematic
Immense. He appears to know every horror perpetrated in the century.