The great Frederick used to compare him to one of those oriental monarchs, who cherish a strict seclusion in order to enhance their importance and majesty.

He did not refuse a pension of some fifty pounds a year from Berlin, and the same amount was bestowed upon him from the privy purse at Versailles.

He received a small annual sum in addition from the Academy.
Though the mathematical sciences remained the objects of his special study, D'Alembert was as free as the other great men of the encyclopaedic school from the narrowness of the pure specialist.

He naturally reminds us of the remarkable saying imputed to Leibnitz, that he only attributed importance to science, because it enabled him to speak with authority in philosophy and religion.

His correspondence with Voltaire, extending over the third quarter of the century, is the most instructive record that we possess of the many-sided doings of that busy time.