Mathematics.- Number theory.- Legendre (Adrien Marie) Essai sur la Théorie des Nombres, second edition, half-title, advertisement f. at end, Paris, Courcier, 1808, bound with Supplément a l'Essai..., folding engraved plate, 4pp. advertisements at end, Février, 1816, together 2 parts in 1 vol., foxing and browning, contemporary straight-grain russet morocco over marbled boards, spine gilt and with green morocco label, spine slightly faded, wear to corners, rubbing to extremities, 4to.

⁂ Second edition of this important work by Legendre, first published in 1797-98, complete with the first supplement published in 1816 (a second appeared in 1825). It contains Legendre's discovery of the law of quadratic reciprocity, which Gauss referred to as the 'golden theorem', as well as his conjecture on the prime number theorem, which he refined in this edition.