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Harker, Alfred

Harker, Alfred

(b. Kingston-upon-Hull, England, 19 February 1859; d. Cambridge, England, 28 July 1939)

petrology.

Harker entered St. John’s College, Cambridge, in 1878 and for sixty-one years was one of its most distinguished members. Although physics was at first his principal subject, in 1884 he was appointed university demonstrator in geology at the Sedgwick Museum at Cambridge and soon became the outstanding figure among British petrologists. His earlier research was conducted chiefly in north Wales and the English Lake District. From 1895 to 1905 he combined his university work with fieldwork in Scotland for the Geological Survey. He received many honors and distinctions, most important among them being the Wollaston Medal of the Geological Society of London (its highest award) in 1922 and a royal medal of the Royal Society in 1935. Somewhat diffident and shy and not readily eloquent in speech, he left writings that are among the masterpieces of scientific literature.

Harker’s original researches concerned five subjects.

1. Slaty cleavage. This was his first study, and the results of it are still authoritative. He returned to it in his later years.

2. North Wales. The igneous rocks associated with the Ordovician sedimentaries in Caernarvonshire had been mapped by the Geological Survey, but Harker described, their exact petrographical nature and discussed their mutual relationships. He traced the connection between the igneous phenomena and the crustal stresses and regional cleavage of the district.

3. English Lake District. Harker made detailed surveys, largely with J. E. Marr, and petrographical examinations of two areas of plutonic and associated rocks: Shap in the south and Carrock Fell in the north. His work here threw light on the problems of igneous variation, differentiation, forms of intrusion and their association, and thermal metamorphism.

4. The islands of the Inner Hebrides. Harker’s studies of the Tertiary igneous activity on the Isle of Skye and the smaller islands to the south inaugurated a new era in the investigation of igneous rock complexes. Principles of the first importance were formulated, such as those of the volcanic-plutonic-hypabyssal cycle and the nature and origin of so-called hybrid rocks. The two memoirs are enduring monuments to his great achievement. The survey work was carried on some twenty years later by a team of the most eminent geologists, who investigated all the Tertiary volcanic centers of western Scotland. In Skye, Harker studied the effects of Pleistocene ice action, emphasizing the importance of glacial erosion.

5. General works. Harker expounded the philosophical results of his research and thought in The Natural History of Igneous Rocks. The whole range of phenomena was examined in the light of the general principles of mathematics, physics, and chemistry, with special attention to geographical distribution and tectonic environment. Metamorphism, one of his latest works, is of the same caliber. Here the beautiful line drawings, a feature of all his works, are especially to be admired. In the first of his two presidential addresses to the Geological Society he reviewed the history of igneous activity in the British Isles throughout geological time. Finally, his Petrology for Students is a work familiar to many generations of college students, particularly treasured by those who were among his pupils.

BIBLIOGRAPHY

I. Original Works. Among Harker’s more important works are “On Slaty Cleavage and Allied Rock Structures,” in Report of the British Association for the Advancement of Science for 1885, pp. 813–852; The Bala Volcanic Series of Caernarvonshire (Cambridge, 1889), the Sedgwick Prize essay; “The Shap Granite and the Associated Igneous and Metamorphic Rocks,” in Quarterly Journal of the Geological Society of London, 47 (1891), 266–328, and 49 (1893), 359–371, written with J. E. Marr; “Carrock Fell: A Study in the Variation of Igneous Rock-masses,” ibid., 50 (1894), 311–337, and 51 (1895), 125–148; Petrology for Students: An Introduction to the Study of Rocks Under the Microscope (Cambridge, 1895; 8th ed., 1954); “Ice-erosion in the Cuillin Hills, Skye,” in Transactions of the Royal Society of Edinburgh, 40 (1901), 221–252; The Tertiary Igneous Rocks of Skye, Memories of the Geological Survey Great Britain (London, 1904); The Geology of the small Isles of Inverness-shire, Memoirs of the Geological Survey of Great Britain (London, 1908); The Natural History of Igneous Rocks (London, 1909); “Some Aspects of Igneous Action in Britain,” in Quarterly Journal of the Geological Society of London, 73 (1917), lxvii–xcvi, his first presidential, address to the Geological Society; Metamorphism: A Study of the Transformations of Rock-masses (London, 1932; 3rd ed., 1950); and The West Highlands and the Hebrides: A Geologist’s Guide for Amateurs, J. E. Richey, ed. (Cambridge, 1941), which includes an appreciation by A. C. Seward (pp. xvii–xxiii).

II. Secondary Literature. On Harker and his work, see “Eminent Living Geologiats: Alfred Harker, M. A., LL.D., F.R.S.,...,” in Geological Magazine, 54 (1917), 289–294; J. S. F[lett], obituary notice in Proceedings of the Geological Society, 96 (1940), lxix–lxxi; A. C. Seward and C. E. Tilley, in Obituary Notices of Fellows of the Royal Society of London, 3 (1940), 197–216; and C. E. Tilley, in Dictionary of National Biography, 1931–1940 (London, 1949), p. 400.

John Challinor

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