Paper, 'Sur les centres de courbure principaux des surfaces homofocales du second ordre' [On the principal centers of curvature of confocal surfaces of the second order] by A [Amédée] Mannheim Mannheim aims to demonstrate some theorems relative to the principal centers of curvature of confocal surfaces, and to show how the six principal centers of curvature of the three confocal surfaces which pass through the same point are geometrically linked. For Mannheim's earlier work on confocal surfaces, see PP/1/26. Annotations in pencil and ink. Includes one geometrical diagram. Subject: Geometry Received 4 March 1882. Read 16 March 1882. Communicated by [Thomas Archer] Hirst. A version of this paper was published in volume 33 of the Proceedings of the Royal Society as 'Sur les centres de courbure principaux des surfaces homofocales du second ordre'. 1882