GNOMONICS -- Juan Bautista CORACHAN (1661-1741). Manuscript, 'Horographia sive Horologiorum Descriptio', Valencia, 1697, the text in red and black ink in a neat cursive hand, with a number of cancellations and emendations (perhaps therefore authorial), including approximately 87 figures (many marginal) and five tables, title and 262 pages, 8vo (163 x 105mm), contemporary pagination (acidification of inking leading to browning throughout and causing erosion of paper to title), contemporary vellum boards (sprung, soiled).
The work, which is constructed as sets of definitions and problems, begins with three preludes concerning basic geometry, cosmography (including a table showing the declination of the sun from a number of cities, chiefly in Spain but also as far afield as Nazareth and Dublin) and gnomonics. Books I-III of the work proper present a series of problems in the construction respectively of direct, reflected and refracted sundials, concluding with discussions of the construction of sundials on cylinders and globes and other recondite problems; a brief appendix considers the analemma. APPARENTLY UNPUBLISHED (not in Palau); a copy is noted in Charles K. Aked, Nicola Severino. Checklist of dialling references (1997).
Juan Bautista Corachan, newly appointed (1696) professor of mathematics at the University of Valencia, was a participant in the scientific salons of the city at the turn of the 17th/18th Century, and composed a number of works aiming to popularise the new science. For Corachan's surviving papers, see Victor Navarro Brotons, 'Inventario de los manuscritos cientificos que figuran en la Biblioteca Mayansiana', Primer Congreso de Historia del Pais Valenciano (Valencia, 1973), vol.1.