Rare overlay "slider" device, which was to be placed over the terrestrial and celestial planisphere maps which were published by Dunn & Owen in their Description and Use of the Universal Planispheres.
Dunn's Universal Planisphere work was published after Dunn became a master at the Academy in Chelsea which specialized in navigation and commerce. His pamphlet was intended to provide "an economical method of teaching spherical geometry without the expense of purchasing actual globes. The pamphlet includes 4 maps, two terrestrial planispheres and two celestial planispheres, each on a stereographic projection, which were intended to imitate the visual and mathematical properties of globes, along with this slider device, which would be placed over the planisphere in order to make calculations.
Examples of "The Earth's Eastern Planisphere" and "The Earth's Western Planisphere" by Samuel Dunn and & William Owen are shown below. The only images of examples of each map can be seen here:
- National Library of Australia: https://nla.gov.au/nla.obj-232418538/view
- Boston Public Library: https://collections.leventhalmap.org/search/commonwealth:cj82m6572
We locate two complete examples of the 1759 edition of the pamphlet with the 4 maps and slider (British Library and Bibliotheque National de France).
We note an example of the map and slider sheet in the Slaughter Collection at the New York Public Library.
Samuel Dunn (bap. 1723-1794) was a teacher of mathematics and navigation who published, among other things, maps and charts. Although information about his early education is lacking, by age nineteen he was leading his own school and teaching writing, accounting, navigation, and mathematics in Devon. In 1751, he moved to London, where he taught in several schools and tutored privately.
By the 1760s, Dunn was known as a respected astronomer and had published a range of textbooks on math, navigation, and astronomy. After the publication of the Nautical Almanac, Dunn acted as a certifier of ships’ masters under the new system, on behalf of the Board of Longitude. He performed similar work for the East India Company, as well as made charts of the East Indies. In 1776 he published A New Variation Atlas and, in 1777, A New Epitome of Practical Navigation, or, Guide to the Indian Seas. By 1780, he was named editor of the New Directory for the East Indies, which included his own charts. In 1786, he released a pioneering study, Theory and Practice of Longitude at Sea. He also designed several instruments for navigation.
Dunn died at his home in Fleet Street in January 1794. His books and maps were auctioned at Sothebys in a sale of over 1,000 lots. Many of these were bought by Alexander Dalrymple, hydrographer of the East India Company and soon-to-be-named first head of the Hydrography Office.