Diagrams of an estimation of the size of Earth by unknown author Diagrams in notes taken from a section on measuring the size of the Earth in Giambattista Riccioli's 'Geographiae et hydrographiae reformatae, nuper recognitae et auctae libri duodecim' [Refromed geography and hydrography recently revised] (1661). Two diagrams. One consists of a circle with an section represented an an angle. The other seems to be the angle. Appears on the fourteenth page of the document. Subject: Astronomy 1662