(b. Dublin, Ireland, 3 June 1810; d. London, England, 5 November 1881)
Mallet’s father, John Mallet, of Devonshire, owned a plumbing business and copper and brass foundry in Dublin, from which he made a large fortune. He married a cousin, also named Mallet. Robert, their only son, was educated at Bective House in Dublin; he entered Trinity College, Dublin, in December 1826, graduating with a B.A. in 1830. After joining his father’s company, he built it up into one of the most important engineering works in Ireland; he himself became an inventive designer-engineer and versatile researcher.
In November 1831 Mallet married Cordelia Watson, who died in 1854. He remarried in 1861. He left two daughters and three sons. Mallet’s eyesight deteriorated seriously after the winter of 1871–1872.
In 1861 Mallet settled in London as a consulting engineer. He edited four volumes of the Practical Mechanic’s Journal (1865–1869), for which he prepared the Journal Record of the Great Exhibition (London, 1862), and, in collaboration with R. F. Fairlie, The Safes’ Challenge Contest at the International Exhibition of Paris in 1867 (1868).
Mallet was a member of many organizations, including the Royal Irish Academy (1832), the British Association (1835), the Institution of Civil Engineers of Ireland (1839, associate; 1842, member; 1866, president), and the Royal Geological Society of Ireland (1847, president). He became a fellow of the Royal Society of London in 1854 and later served as a member of its council. Mallet also received an honorary doctor of laws degree from Trinity College and was awarded numerous scientific medals.
Among Mallet’s notable technical accomplishments were the erection of the roof of St. George’s Church in Dublin with hoists of his own design; his “manumotive” for baggage transport, which, with eight men driving it, covered the five miles from Dublin to Kingstown in twenty minutes (1834); his procedure for the electromagnetic separation of brass and iron filings; and his method of bleaching turf for the manufacture of paper (1835). His multifarious engineering projects also involved work on steam-driven printing plants, bridges, hydraulic presses, ventilators and heaters, brewery machinery, railroads, dock gates, viaducts, lighthouses, and coal mines. Mallet worked out a plan to supply Dublin with water from six reservoirs on the Dodder, for which he carried out the surveying at his own expense in 1841. His name is associated with the “buckled plates,” which he patented in 1852, used for flooring and later for railroad ties.
From 1850 to 1856 Mallet worked on the design of heavy guns. With his comprehensive account entitled The Physical Conditions Involved in the Construction of Artillery, With an Investigation of the Relative and Absolute Values of the Materials Principally Employed, and of some Hitherto Unexplained Causes of the Destruction of Cannon in Service (Dublin, 1856), he created a basis for later books on ordnance and on casting and founding.
In view of these many technical achievements and the demands of running such a large business, it is remarkable that Mallet still found time for scientific research in the most varied fields. Among his scientific papers are investigations of the “seed-dispersing apparatus” of Erodium moschatum (1836); the blackening of photographic paper due to the radiation of glowing cinders (1837); the photochemical bleaching of caustic potash; the effect of boiling on organic and inorganic substances (1838); the improvement of the manufacture of optical glasses; and the application of the “electrotype process in conducting organic analysis” (1843).
The author of fundamental works on the effect of air and water—especially pure and polluted seawater —on wrought and cast iron and also on steel (1836—1873), Mallet is one of the founders of research on corrosion. In this way and through his studies dealing with the physical properties and electrochemical relationships of copper and tin alloys with tin and zinc, he made important early contributions to the science of materials. He also dealt with the state of aggregation of alloys (1840–1844), with the coefficients of elasticity and with failure in wrought iron (1859), and with the expansion of cast iron (1875).
Completely aside from his profession as an engineer, Mallet was interested in the structure of County Galway trap and the columnar structure of basalts, and in glacier movement, the plasticity of glacial ice, and the lamination of Irish slates.
Stimulated by Charles Lyell’s description of the earthquake in Calabria in 1783, Mallet explained its “vorticose movement” by the position of the center of gravity, adhesion, or—as the case may be —friction, and the inertia of the squared stone affected by the tremor (1846). In the same year he presented to the Royal Irish Academy his On the Dynamics of Earth quakes. In this work he differentiated the So-called earth wave, great sea wave, forced sea wave, and aerial or sound wave. Mallet considered local elevations of portions of the earth’s solid crust to be the cause of earthquakes. He produced an experimental seismograph in 1846. Important elements of his model, which was never actually used, were incorporated in the seismograph that Luigi palmieri made in 1855. Between 1850 and 1861 Mallet set off explosions in different locations to determine the rate of travel of seismic waves in sand (825 feet per second), solid granite (1, 655 feet per second), and quartzite (1,162 feet per second). According to A. Sieberg (1924), Mallet should be considered the founder of the physics of earthquakes. The term “seismology” we owe to Mallet, as well as “seismic focus,” “angle of emergence,” “isoseismal line,” and “meizoseismal area,”
Mallet presented his most important seismic results in four Report[s] to the British Association (1850, 1851, 1852–1854, 1858) and in four editions of the Admiralty Manual of Scientific Enquiry (1849, 1851, 1859, 1871), Between them, they contain an extensive catalog—which he prepared and debated with his son, John W. Mallet—of 6,831 earthquakes reported between 1606 B.C. and A.D. 1858 and his seismic map of the world. In February 1858 he visited the region of the Neapolitan earthquake of 16 December 1857. In 1869, with Oldham, he developed a spherical Projection seismograph.
Through his work in seismology, Mallet encountered possible connections with vulcanicity. He eventually studied the problem of the emergence of volcanic foci in particular. In 1862 he published “Proposed Measurement of the Temperatures of Active Volcanic Foci to the Greatest Attainable Depth…” (Report of the British Association for the Advancement of Science for 1862). In 1872 he submitted his principal paper on vulcanicity, “Volcanic Energy; an Attempt to Develop Its True Origin and Cosmical Relations” (Philosophical Transactions of the Royal Society, 163 , no. 1 , 147–227).
In 1870 Mallet made exhaustive analyses of sixteen different types of rock. Through computations he concluded that (1) “the crushing of the earths’s solid crust affords a supply of energy sufficient to account for terrestrial vulcanicity”; and (2) that “the necessary amount of crushing falls within the limits that may be admitted as due to terrestrial contraction by secular refrigeration” (ibid., P. 214). Although this theory received little attention in the following years, it nevertheless contained some ingenious conceptions that were taken over by later researchers. In any case, it deserves recognition as an early example of the mathematical utilization of experimental findings in the services of geological speculations.
I. Original Works. A list of eighty-five (incorrectly numbered ninety-one) papers by Mallet is in Royal Society Catalogue of Scientific papers, IV. 205–208; VIII, 314; X, 703–704. See also Poggendorff, III, Pt. 2, 861–862.
In addition to works cited in the text, Mallet wrote Great Neapolitan Earthquake of 1857: The First Principles of Observational Seismology, 2 vols. (London, 1862). Works which he translated and to which he contributed include H. Law, Civil Engineering (London, 1869), with Mallet’s notes and illustrations; G. Filed, The Rudiments of Colours and of Colouring (London, 1870), revised and partly rewritten by Mallet; L. L. de Koninck, A Practical Manual of Chemical Analysis and Assaying (London, 1872), which he edited and to which he contributed notes; and L. Palmieri, The Eruption of Vesuvius in 1872 (London, 1873), with notes and intro. by Mallet.
II. Secondary Literature. For obituaries of Mallet, see Engineer, 52 (1881), 352–353, 371–372, 389–390; Minutes of Proceedings of the Institution of Civil Engineers, 68 (1882), 297–304; Proceedings of the Royal Society, 33 (1882), 19–20; and Quarterly Journal of the Geological Society of London, 38 (1882), 54–56.
See also (listed chronologically) Dictionary of National Biography, XXXV (1893), 429–430, which gives Mallet’s place of death as Enmore, Surrey; R. Ehlert, “Zusammen stellung, Erläuterung und kritische Beurtheilung der wich tigsten Seismometer,” in Beiträge zur Geophysik, 3 (8198), 350–475; K. A. von Zittel, Geschichte der Geologie und Palãontologie bis Ende des 19. Jahrhunderts (Munich, 1899); Charles Davison, The Founders of Seismology(Cambridge, 1927): and L. Mintrop, “100 Jahre physikalische Erdbebenforschung und Sprengtechnik,” in Naturwissenschaften, 34 (1947), 257–262, 289–295.