A Geometric Chuck is used for cutting patterns made up of rolling centres. The details are difficult to explain, and are better explained by John Edwards' document.
This chuck is so complicated that John Jacob Holtzapffel never got around to putting it into his last published work, Turning and Mechanical Manipulation, vol. 5 - The Principles and Practice of Ornamental or Complex Turning (1884).
There is an article about one in the "English Mechanic and Mirror of Science", Vol VII, No. 171 (03 July 1868).
Thomas Bazley published a book, Index to the Geometric Chuck about this chuck.
John Edwards captured this and more in what he calls the "Holtzapffel Volume 6". You can get a copy from the The Society of Ornamental Turners.
This is a YouTube video from Chuck Bommarito (aka, outsidescrewball) showing a Leinhard Rose Geometric Chuck in use. The video is a bit long, but does show the chuck well, as well as a piece made on it.