"S. Dunn - Teacher of the Mathematicks, London. Boards young gentlemen, & Teacheth Penmanship, Merch'ts Accounts, Navigation. Fortification, Astronomy &c. Chelsea"
"S. Dunn - Teacher of the Mathematicks, London. Boards young gentlemen, & Teacheth Penmanship, Merch'ts Accounts, Navigation. Fortification, Astronomy &c. Chelsea" | | |
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Samuel Dunn 1723 - 1794 | |||
Samuel Dunn (1st cousin, 6x removed) is one of the few forebears that you will encounter on this site who made his mark beyond the circle of his friends and family. At the tail end of the Enlightenment, he was an astronomer, geographer, cartographer and teacher of mathematics and navigation, and as such, very much a product of that period of Reason and Science.
| Samuel Dunn | ||
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Some of Dunn's Publications
Dunn's Inventions or Discoveries
| Life of Dunn 1723 born in Crediton, baptised in Parish Church on 7 February 1741 Teaching writing, accounts and navigation in his own school 1743 School destroyed in one of Crediton's fires 1751 Moves to London 1758 Master of an Academy at Ormond House, Paradise Row, Chelsea 1758 Proposes the opening, by subscription, of a Philosophical Lyceum or Experiment Room, "for shewing the Principles of Natural Philosophy" 1760 Observes a Comet from the school's observatory 1761 Observes the Transit of Venus 1761 Designs an angular micrometer 1764 Visits Paris 1769 January 6th. One of three teachers authorised by the Lords of the Admiralty to sign ships' masters' certificate of competence in Navigation 1768 Designs Sextant for taking large angles 1769 Invited by Astronomer Royal to observe the Transit of Venus 1770s An approved teacher for the East India Company 1777 Living at 8 Maiden Lane, Covent Garden 1780 Appointed Editor of the New Directory for the East Indies, living at 1 Boars Head Court, Fleet Street 1788 Appointed as Examiner in Mathematics for East India Company cadets 1794 Died and was buried at St Dunstan in the West, on 23rd January 1794 Dunn's legacy funds a teacher in Crediton | ||
When the Nautical Almanac was introduced (for the year 1767) the Board of Longitude ruled that all ships' masters appointed henceforth had to have a certificate of competence, and until 1771 Dunn was among the teachers authorized to sign these certificates. Dunn was involved with the East India Company and from the 1770s he prepared charts for far eastern waters. In A New Variation Atlas (1776). and A New Epitome of Practical Navigation, or, Guide to the Indian Seas (1777), dedicated to the company, Dunn introduced an original solution to the double-altitude problem. Where the approximate latitude was known two observations were to be taken of the sun's altitude, and the time elapsed between observations noted; calculations following Dunn's formula then yielded the true latitude. This solution was a remarkable discovery and later formed the basis of the 'trial and error' method for finding longitude. It also led towards position-line navigation. |
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| In 1780 he succeeded William Herbert as editor of the New Directory for the East Indies. He applied himself in picking out the safest and most direct routes to the East Indies and other parts of the world: and in 1787 the East India Company's hydrographer, Alexander Dalrymple, made plates of his charts available so that Dunn could group and print them for the sixth edition of the Directory. In 1788 a committee appointed by the Company to report on Dunn formed so high an opinion of his abilities that he was engaged as examiner in mathematics to their cadets, and in 1792,when presenting the Company with one of his newest works, he expressed the wish that it would be instrumental in preserving their valuable shipping. | ||
Dunn also sought to improve instruments for navigation and cartography. An angular micrometer which he demonstrated to the Royal Society in May 1761 was made for him by the firm of Heath and Wing in the Strand, and his pantograph, described in The Theory and Use of the Pantographer (1771), was made by their successor, Thomas Newman. In 1768 he showed to the board of longitude models of a sextant for taking large angles, for which he was awarded £20. Not all Dunn's proposals to the board of longitude met with approval. His method of finding the longitude of ports and another for drawing magnetic isolines at sea were rejected, for example. His Theory and Practice of Longitude at Sea (1786), dedicated to the Company of Merchants, was however ahead of its time. Watches were still rare in his day and the method matured only after his death. The family story about Samuel is that he was tutor to King George III. I have not yet found any evidence for this, but in the Exeter Flying Post of 30 July 1887, the same story was printed as fact by the newspaper. What seems to be certain is that he advanced the science of navigation considerably; he was an inventor, an innovator, an artist and an entrepreneur. He is all but forgotten by his home town though his legacy in more ways than one was a rich one for the town, and for the nation. His maps and prints are still widely available today on the internet. |
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In 1758 Dunn became master of an academy at Ormond House, Paradise Row, Chelsea, where he seemed to have taken advantage of the good observatory located at the school. He observed a comet there in January 1760 and was able to observe and record the transit of Venus in 1761. A transit of Venus across the sun takes place when the planet Venus passes directly between the Sun and the Earth obscuring a small portion of the Sun's disc. During a transit, Venus can be seen from the Earth as a small black disc moving across the face of the Sun. Transits appear in pairs separated by gaps of eight years only every 120 years or so. When the second transit of the pair was due, Dunn was well known, and it was proposed that his sextant for taking large angles be tested by an expedition going to the Arctic regions to observe the 1679 transit. Dunn himself was invited by the Astronomer Royal to observe the transit from the Royal Observatory, Greenwich, in the evening of 3 June, which he did in the company of Maskelyne - an extract from his account below.
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Dunn's observations comparing the 1761 and 1769 Transits
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Dunn's School |
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Being childless Dunn's estate went to his cousins at Crediton, William, Thomas and Mary Dunn [my g-g-g-g-grandmother]. And a bequest of £600 in Bank of England 5 per cents was allocated for the funding of a teacher (the appointment to be overseen by twelve Governors of the Church in Crediton) at the sum of £30 per year, at the Bowden Hill School in Crediton where Dunn had once taught, in which "writing, navigation, the lunar methods of taking longitude at sea, planning, drawing and surveying" should be taught to six boys, preferably those named Dunn or Harris, otherwise to boys of the district belonging to the Established Church. The master was to be of the Church of England, but not in Holy Orders. | |||
 Paper given by Dunn to the Royal Society Samuel seems to have singularly failed to be accepted by learned societies. His numerous papers notwithstanding, he was not made a Fellow of the Royal Society. There are references on the internet to his membership of the Philosophical Society of America. Indeed he may have asserted as much himself, but though he sought membership he never was admitted. He wrote to the Society naming illustrious Benjamin Franklin as a possible proposer. "Gentlemen, I sent you last year my Observations on the Transits of Venus in 1761 & 1769. I now send herewith a Chart of the Stars used in finding the Longitude of the Moon, invented by me, & Engraved (tho' Coarsely) with my own hands. Dr. Franklin will do the Honour of proposing me to be a Member of your Society. Your most Obedt. Humble Servant " For whatever reason, membership was not forthcoming. |
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This site was last updated 24/03/08
Bowden Hill, Crediton, today
