Early life

He was born to John and Alice Dunn in Crediton, Devonshire, and baptised there on 7 February 1723. His father died at Crediton in 1744. Samuel Dunn wrote in his will:

In 1743, when the first great fire broke out and destroyed the west town, I had been some time keeping a school and teaching writing, accounts, navigation, and other mathematical science, although not above twenty years of age; then I moved to the schoolhouse at the foot of Bowdown [now Bowden] Hill, and taught there till Christmas 1751, when I came to London.^[1]

The schoolhouse was the place where the "English school" was kept previously to its union with the blue school in 1821.

Life and career in London

Dunn moved to London in December 1751, where he taught in different schools, and gave private lessons.^[1] In 1757, he came before the public as the inventor of the "universal planispheres, or terrestrial and celestial globes in plano", four large stereographical maps, with a transparent index placed over each map,

whereby the circles of the sphere are instantaneously projected on the plane of the meridian for any latitude, and the problems of geography, astronomy, and navigation wrought with the same certainty and ease as by the globes themselves, without the help of scale and compasses, pen and ink.^[1]

He published an account of their Description and Use, 2nd edition, octavo, London, 1759. From the preface, it appears that in 1758 Dunn had become master of an academy "for boarding and qualifying young gentlemen in arts, sciences, and languages, and for business", at Chelsea. It was the Maritime Academy, at Ormond House, Paradise Row^[3] where there was a good observatory.^[1]

On 1 January 1760, he made the observation of a remarkable comet.^[4] Other discoveries he communicated to the Royal Society; between 1761 and 1771, Dunn contributed nine papers to the Philosophical Transactions of the Royal Society, of which body, however, he was not a fellow.^{[5][6][7][8][9][10][11][12][13]} On the title-page of his Atlas he appears as a member of the Philosophical Society at Philadelphia, America. A few of his letters to the historian Thomas Birch are preserved,^[14] and one to the botanist Emanuel Mendes da Costa.^[15]

Dunn married Elizabeth Harrison in 1763. Towards the close of 1763, he gave up the school at Chelsea, and fixing himself at Brompton Park, near Kensington, resumed once more his private teaching. In 1764 he made a short tour through France.^[16] In 1774, when residing at 6 Clement's Inn, near Temple Bar, he published his excellent New Atlas of the Mundane System, or of Geography and Cosmography, describing the Heavens and the Earth. … The whole elegantly engraved on sixty-two copper plates. With a general introduction, folio, London (second and third editions of which appeared in 1788 and 1789, respectively). About this time his reputation led to his being appointed mathematical examiner of the candidates for the East India Company's service.^[1]

Under the company's auspices he was enabled to publish in a handsome form several of his more important works. Such were:^[1]

1. A New and General Introduction to Practical Astronomy, with its application to Geography … Topography, octavo, London, 1774.
2. The Navigators Guide to the Oriental or Indian Seas, or the Description and Use of a Variation Chart of the Magnetic Needle, designed for shewing the Longitude throughout the principal parts of the Atlantic, Ethiopic, and Southern Oceans, octavo, London (1775).
3. A New Epitome of Practical Navigation, or Guide to the Indian Seas, containing (1) the Elements of Mathematical Learning, used … in the Theory and Practice of Nautical affairs; (2) the Theory of Navigation. ..; (3) the Method of Correcting and Determining the Longitude at Sea …; (4) the Practice of Navigation in all kinds of Sailing (with copper plates), octavo, London, 1777, and
4. The Theory and Practice of the Longitude at Sea … with copper plates, octavo, London, 1778; second edition, enlarged, quarto, London, 1786.^[17]

He also "methodised, corrected, and further enlarged" a goodly quarto, entitled A New Directory for the East Indies … being a work originally begun upon the plan of the Oriental Neptune, augmented and improved by Mr. Willm. Herbert, Mr. Willm. Nichelson, and others, fifth edition, London, 1780, with a sixth edition following in 1791. Dunn was living at 8 Maiden Lane, Covent Garden, in July 1777, but by September 1780 had taken up his abode at 1 Boar's Head Court, Fleet Street, where he continued for the remainder of his life.^[18]

Death and legacy

He died in January 1794. His will, dated 5 January 1794, was proved at London, on 20 January by his kinsman, William Dunn, officer of excise of London (registered in P.C.C., 16, Holman).^[19] Therein he describes himself as "teacher of the mathematics and master for the longitude at sea", and desires to be buried "in the parish church belonging to the place where I shall happen to inhabit a little time before my decease". He names seven relations to whom he left £20 each; but to his wife, Elizabeth Dunn, "who hath withdrawn herself from me near thirty years, the sum only of ten pounds". No children are mentioned.^[18] His library and instruments were sold at auction.^[20]

He also requested the corporation of Crediton to provide always and have a master of the school at the foot of Bowden Hill residing therein, of the church of England, but not in holy orders, an able teacher of writing, navigation, the lunar method of taking the longitude at sea, planning, drawing, and surveying, with all mathematical science. For this purpose he left £30 a year. Six boys were to be taught, with a preference to his own descendants. The stock thus bequeathed produced in 1823 dividends amounting to £25 4/- per annum, the school being known by the name of Dunn's School.^[21]