# Dictionary of National Biography, 1885-1900/Pepys, William Hasledine

​PEPYS, WILLIAM HASLEDINE (1775–1856), man of science, born in London on 23 March 1775, was the son of W. H. Pepys, a cutler and maker of surgical instruments in the Poultry, London; he was descended from Sir Richard Pepys [q. v.] In March 1796 he helped to found the Askesian Society (see Life of W. Allen, pp. 26, 45), which eventually led to the foundation of the British Mineralogical and Geological Societies and the London Institution, of which he was one of the original managers, and honorary secretary from 1821 to 1824. His name appears as treasurer, and afterwards as vice-president, of the Geological Society in the first volumes of their ‘Transactions’ (beginning in 1811). He was also an early member of the Mineralogical Society. He appears to have succeeded to his father's business in the Poultry, and to have extended it to philosophical-instrument making. He was a close friend of William Allen (1770–1843) [q. v.], with whom he did most of his best work, and also was intimate with Luke Howard (1772–1864) [q. v.] Like these men, Pepys was a quaker. In 1798 he worked with Desvignes on soda-water apparatus (Tilloch, Phil. Mag. iv. 358). In 1808 he was elected F.R.S. He took an active part in the management of the Royal Institution, of which he was president in 1816. He died at his house in Earl's Terrace, Kensington, on 17 Aug. 1856.
Pepys had remarkable skill and ingenuity in inventing apparatus, and many important devices are due to him. His mercury gasometer (suggested by a piece of apparatus of Watt's) and his water gasholder are still used in practically their original form. He was one of the first, if not the first, to use mercury contacts for electrical apparatus (ib. xli. 15) and tubes coated with indiarubber (ib. xi. 256) for conveying gases. In 1801 he connected the newly discovered voltaic pile with an electroscope and condenser of his own devising, and showed thus that ‘the electric and galvanic fluid possessed identity’ (ib. x. 38). The experiment had, however, been made previously by Volta (Philosophical Transactions of the Royal Society, 1800, p. 406). In 1807 he invented an ingenious eudiometer, which he calibrated by a method still used for the purpose (ib. 1807, p. 247; and Bunsen's Gasometry, translated by Roscoe, p. 29).
Pepys was in general rather occupied with the invention than the use of apparatus. His chemical work does not show originality. His most important researches were carried out with Allen. The experiments on the combustion of diamond, graphite, and charcoal, yielded a valuable confirmation of the results of Smithson Tennant [q. v.], Guyton de Morveau, and Mackenzie (Kopp, Gesch. der Chemie, iii. 292); and the very careful and well-reasoned work on respiration, executed with apparatus for the most part invented previously by Pepys, and allowing the experimenters to repeat the investigation of Lavoisier and Séguin more accurately and with some variations, is still quoted in the textbooks. The chief result was to show that the volume of carbonic acid expired from the lungs is almost exactly equal to the volume of oxygen abstracted from the inspired air.
* ‘On the Production of Cold,’ iii. 76, 1799.
* ‘[On] a Mercurial Gasometer,’ v. 154, 1799.
* ‘[On] a Newly Invented Galvanometer,’ x. 38, 1803.
* ‘An Improved Chemical Apparatus … ​by which Absorption is completely prevented and Liquids may be strongly impregnated with the different Gases,’ xi. 253, 1801.
* ‘Analysis of the Satin Spar,’ xii. 365, 1802.
* ‘[On] a new Gas-holder,’ xiii. 153, 1802.
* ‘On Gems,’ xvii. 193, 1803.
* ‘Analysis of Human Teeth,’ ib. p. 313.
* ‘Analysis of Shetland Iron,’ xix. 86, 89, 1804.
* ‘A new Apparatus for the Decomposition of Alkalies,’ xxxi. 241, 1808.
* ‘[On] the Decomposition of Sulphate of Iron by Animal Matter,’ xxxviii. 297, 1808.
* ‘A Mercurial Voltaic Conductor,’ xli. 15, 1813.
In the ‘Philosophical Transactions of the Royal Society’:
* ‘A new Eudiometer,’ p. 247, 1807.
* ‘The Respiration of Leaves,’ p. 329, 1843.
* ‘An Apparatus for Performing Electro-Magnetic Experiments,’ p. 187, 1823. In the ‘Journal of Science and the Arts:’
* ‘A new Construction of the Voltaic Apparatus,’ vol. i. pt. ii. p. 193, 1816.
* ‘An Improved Apparatus for the Manufacture of Soda-water,’ iv. 358, 1818.
* ‘A New Form of the Voltaic Apparatus,’ xv. 143, 1823 (refers to the apparatus described in No. 15).
In Horticultural Society's ‘Journal’:
In collaboration with Allen he published the following papers in the ‘Philosophical Transactions of the Royal Society’:
* ‘On the quantity of Carbon in Carbonic Acid, and on the Nature of the Diamond,’ 1807, p. 267.
* ‘On … Respiration,’ 1808, p. 249.
* ib., 1809, p. 404.
* ‘On the Respiration of Birds.’
[Besides the sources quoted above, Knight's English Cyclopædia; Gent. Mag. 1856, i. 521; J. C. Poggendorff's Biogr. Lit. Handwörterbuch zur Gesch. der exacten Wissenschaften; Life of William Allen, 3 vols. 1846–7, passim; Transactions of the Geological Society, vol. i. 1811, &c.; Royal Society's Catalogue of Scientific Papers, vol. iv.; Hermann's Physiology Trans., Gamgee, p. 158; Landois and Stirling's Physiology, 1st edit. p. 259; account of the Ornithorhynchus paradoxus (belonging to W. H. P.), Tilloch's Phil. Mag. xiii. 179, 256; and Pepys's own papers and his collection of manuscript papers relating to the Royal Institution in the Brit. Mus. Library.]
P. J. H.