Title: Thornton's Portolan Map
Artist: Thornton, John

This lovely decorative chart is by John Thornton, an English chartmaker of the Thames School. It is an unusually late example of a portolan chart. Thornton was Hydrographer to the East India Company and produced many maps, both manuscript like this one and printed.

[Map of the Indian Ocean], by John Thornton, 1682. Map Res 117