From these nights of meditation he was beginning, he thought, to grok "business," and "money," and "buying," and "selling," and related un-Martian activities - the articles in the Encyclopedia had always left him feeling unfilled, as (he now grokked) each one had assumed that he knew many things that he did not know.  But there arrived in the mail, from Mr. Secretary General Joseph Edgerton Douglas, a check book and other papers, and his brother Jubal had taken great pains to explain to him what money was and how it was used.