“Among his favorite studies, I will cite especially his figurative maps and his graphic tables, the use of which he popularized and to which he attached a well merited importance; because for the dry and complicated columns of statistical data, of which the analysis and the discussion always require a great sustained mental effort, he had substituted images mathematically proportioned, that the first glance takes in and knows without fatigue, and which manifest immediately the natural consequences or the comparisons unforeseen.”