Although Roget's association with Manchester was short, he was an officer of the Literary and Philosophical Society and the first secretary of the Portico Library when it was founded in 1806. He was a remarkable man in the fields of medicine, mathematics and literature.

Peter Roget was born in London, the only son of Rev. John Roget, a Swiss born pastor in the French Protestant Church in Threadneedle Street. His mother was a sister of Sir Samuel Romilly. Peter's father died when Peter was young and following this the family moved to Edinburgh. There he entered the university at the age of 14, studied mathematics and medicine and graduated with the degree of MD at the age of 19. Later he studied at the London Medical Schools under Baillie, Cruickshank, Wilson, Heberden and Horne.

In 1802, during the Peace of Amiens, he visited Paris and then his father's home town of Geneva, while acting as tutor for the sons of a Manchester merchant. When hostilities resumed, Roget was imprisoned for two months but then allowed to return to England in 1803. For a time he was the travelling attendant of the Marquis of Landsdowne.

Roget was particularly interested in tuberculosis and in the effects of inhaling laughing gas (nitrous oxide). Later in life he wrote an article on Thomas Beddoes of Bristol, famous for his investigation of gases of possible medical use. When Thomas Percival died in 1804, Roget was offered the position of chief surgeon at the Manchester Infirmary, a post he held until 1808. He was a Vice President of the Manchester Literary and Philosophical Association for two years and became the first secretary of the Portico Library in 1806. While in Manchester Roget played an important role in founding a medical academy.


The Portico Library and Gallery, Mosley Street, Manchester

Roget left Manchester to teach in the London Medical School in Windmill Street in 1808. He became a Licentiate of the College of Physicians and became physician to the Northern Dispensary in 1810. In 1811, he became one of the secretaries of the Medical and Chirugical Society of London and he was elected president in 1829/30. In 1828 he published a report on London's water supply and for three years was Fullerian Professor of Physiology at the London Institute.

In 1814, Roget invented a machine for determining the powers and roots of numbers. The slide rule was already known as a device for multiplying and dividing numbers. It is based on the idea that the multiplication of two numbers can be achieved by adding their logarithsms. Roget extended the idea so that powers and roots of numbers could be found. For example the cube of a number is found by multiplying its logarithm by three and the cube root by dividing the logarithm by three. He devised a slide rule that would do this by adding the logarithms of the logarithms. This type of slide rule was invaluable to scientists and engineers until the invention of the pocket calculator. Roget's invention brought him to the attention of the scientific establishment when he published it in Philosophical Transactions in 1814 and he was elected a Fellow of the Royal Society. Following the death of Sir John Hershell, Roget was secretary of the Royal Society from 1827 to 1848. He also invented a pocket chessboard. For a number of years from 1820 he was the physician for the Spanish Embassy. In 1833 Roget published his Treatise on Animal and Vegetable Physiology.

In 1824, Roget made important observations in the field of optics. His observations were based initially on looking at the world through a series of slits such as one might have in a vertical Venetian blind or pallisade. A rotating cartwheel viewed through such as system gives an optical illusion. The spokes at the top and bottom appear straight but those at the sides appear to bend downwards. Roget worked out the path of the light to show how this happened. He went on to explain a phenomenon that often perplexes devotees of Westerns, a hundred years before the invention of film. At certain speeds, the cartwheel appears to stop or go backwards. Roget's observations were made by viewing through vertical slits but he showed the position of each spoke in the wheel at each glimpse and how this could lead to the optical illusion of stasis or backward motion. The same phenomenon is observed when a film is made with a cine camera. In 1820, Roget worked with Michael Faraday and Joseph Plateau in a series of experiments on vision leading to Roget's paper to the Royal Society on the Persistence of Vision. Roget's work showed that an image persists in human perception for about one sixteenth of a second and this forms the basis on which animations, film and television are based.

Roget also made experiments in electricity and magnetism and showed that there was an attractive force between parallel wires carrying current in the same direction. He invented an apparatus with a helical wire ending in a small iron sphere. The iron dipped into a pool of mercury to form an electrical contact. When the current flowed through the wire, the attraction between adjacent coils caused the helix to contract, lifting the iron sphere from the mercury. The process then repeated causing a bobbing motion. He published this work in 1835 and the apparatus is sometimes knows as Roget's spiral.

In 1840 he retired from medicine and began work on his Thesaurus of English Words and Phrases Classified and Arranged so as to Facilitate the Expression of Ideas and Assist in Literary Composition. It was first published in 1852 but went through 28 editions and reprints in his lifetime. About 1850, Roget founded the Society for the Dissemination of Knowledge. He died at the age of 90 on 12 September 1869 at West Malvern.



1.  The following books and articles by Roget formed part of an exhibition on scientists and medical men at the Portico Library and Gallery in February 2003.

Explanation of an optical deception in the appearance of the spokes of a wheel seen through a vertical aperture, by Peter Mark Roget, published by W. Nichol of London, 1825 from an article in Philosophical Transactions. The article was in Philosophical Transaction of the Royal Societty of London, 1825, part 1, page 131, and has been viewed at Manchester Central Library. The key points are as follows:

When spokes of a wheel seen through vertical slilts such as a pallisade or vertical Venetian blind they take on a curvature. The spokes at the top and bottom appear straight. Those that are horizontal appear most distorted. On both sides of the wheel the spokes appear to be curved downwards. The wheel is rotated at increasing speed and initially the curvature is seen only on the horizontal spokes, when the speed is increased slightly it shows suddently on all but the vertical ones but a further increase of speed does not increase the effect. If the bars through which the phenomenon is observed are not vertical the spokes bending most are at 90 degrees from the angle of the bars. The optical illusion ceases if the bars are parallel to the line of motion.

An Introductory lecture on human and comparative physiology, by Peter Mark Roget, Longman et al., London 1826.

Animal and Vegetable Physiology considered with reference to Natural Theology, by Peter Mark Roget, published by William Pickering, 2 Vols., London 1834.

Cranioscopy, by Peter Mark Roget, from a supplement to the Encyclopaedia Britannica.

Description of an instrument for performing mechanically the by Peter Mark Roget, published by W. Bulmer and Co., London, 1815, from Philosophical Transactions of the Royal Society, 1815, part 1, page 9.

2. There is an article on Roget on the web pages of BBC History

3. Boomtown Manchester, 1800-1850, The Portico Connection, A History of the Portico Library and Newsroom and the influence of the founding members on the development of Manchester, by Ann Brooks and Bryan Haworth, published by the Portico Library, 57 Mosley Street, Manchester, 1993, ISBN 0-9519168-0-7. Chapter Five looks at the medical men associated with the library.

4. Portico Library: A History, by Ann Brooks and Bryan Haworth, Carnegie Publishing, 2000, ISBN 1-85936-070-X.

5. Obituary notice in the Times of London, 17 September 1869, page 7, column d. viewed at Manchester Central Library.


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