Jeffreys, John Gwyn

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Jeffreys, John Gwyn

(b. Swansea, Wales, 18 January 1809 ; d. London, England, 24 January 1885)

marine zoology.

Jeffreys was the eldest son of john Jeffreys, a solicator. He was articled to a solicator at seventeen but, as his tastes were scientific rather than legal he spent his holidays dredging from a rowboat in Swansea Bay. When only nineteen he submitted “A synopsis of the Testaceous Pneumonobranches mollusca of Great Britain” to the Linnean Society and was elected a fellow the following year. In 1840 Jeffreys married Anne Nevill, and in the same year he was elected fellow of the Royal society and received an honorary LL.D from St.Andrews University.

Jeffreys practiced as a solicator untill 1856, When he was called to the bar at Lincoln” Inn. Although he could spare only short holidays, each summer from 1861 to 1868 was spent dredging, mostly to the north and west of scotland. In 1866 he retired from the legal profession to devote all his time to the study of the European Mollusca. His discoveries early led him to suspect that the present-day malacofauna is directly descended from that of the late Tertiery deposits, as he found many crag mollusks, formerly supposed to be extinct still living in the seas around shetland and the Hebridges. After publishing numerous short papers on the results of his explorations, Jeffreys brought out a five-volume systematic treatise, British Conchology, which remains a standard work of reference on the subject to this day.

In 1843 Edward Forbes had postulated that no life wouldbe found in the sea below a limit of about 300 fathoms. This was still generally believed in the 1860” althoughs by then enough evidence had already come to light to have made the hypothysis no longer tenable. In 1868 a successful haul had been made from 650 fathoms.during the experimental cruise of H.M.S Lightning, demonstrating the possibility of exploring depths rather greater than the 200 fathoms to which most previous dredging had been confined. That cruise also cast doubt on the then current belief that the temperature of sea water is a constant 4°C below a certain depth. In 1869 and 1870 the Admiralty survay ship Porcupine was made available for further oceangraphic investigatons, and Jeffreys was given charge of the scientific work on two of her cruises.

A great number of new spices, especially of mollusks, were collected with other previously known only as Tertiary fossils. The dredge was successfully worked to a maximum depth of 2,435 fathoms and life wasfound to be present at all levels. The existence of cold- water and warm- water areas in close preximity at similar depth was also confirmed. Thus two prevalent ideas- the azoic zone and the universal minimum temperature-were shown conclusively to be false. From a conchological point of view, the cruises of the Lightning and porcupine yielded considerably more material than the subsequent and much more extensive voyage of the Challenger; and the mollusks obtained occupied Jeffreys for the rest of his life. In 1875 he superintended the deep - sea explorations of H.M.S Valorous, which accompained the Arctic expedition of Captain sir George S. Nares as far as Baffin Boy; and in 1880, by invitation of the French government, he took part in dredging the deep water of the Bay of Biscay on board the Travailleur. This was Jeffrey’ last active participation in marine research. In 1889 he was one of the founders of the Marine Biological Association of the United Kingdom.

Jeffreys appreciated more than any conchologist before him the necessity for careful comparison with good series and actual specimens of types. For this purpose he visited all the principal European collections and added extensively to his personal collection by exchange and purchase. This collection was unrivaled for British mollusks and also contained a very extensive series of Mediterranean, Scandinavian, and Arctic spices. His exact knowledge of resent European mollusks made his openions on those of the late Tertiary deposits of particular value, and the latter too were well represented in his collection. Jeffrey “collections was intended for the British Museam but, as a result of a disagreement with those in authority there, it was sold to the smithsonian Institution for a thousand guineas a few years before Jeffrey’death.


1. Original Works. Jeffrey’ major work is British Conchology, or an Account of the Mollusca Which Now Inhabit the British Isles and the Surrounding Seas, 5 vols. (London, 1862-1869), vol. I (only) repr. 1904. More than 100 papers on European mollusks are listed in the Royal SocietyCatalogue of Scientific Papers. 3 (1869), 541–542; 8 (1879), 20; 10 (1894), 332–333; 12 (1902), 366; 16 (1918), 93, of which the most important are “Preliminary Report of the Scientific Exploration of the Deep Sea in H. M. Surveying-Vessel ‘Porcupine’ During the summer of 1869’ in Proceedings of the Royal Society, 18 (1870), 397-492 written with W.B. Carpender and C. Wyville Thomson’‘New and Peculiar Mollusca . . . Procured in the‘Valorous’ Expedition ’ in Annals and Magazine of Natural History, 4th ser., 18 (1876), 424–436, 490–499, and 19 (1877), 153-158 231–243, 317–339; “On the Mollusca Procured During the ‘Lightning’ and ‘Porcupine’ Expeditions, 1868–70,” in Proceedings of the zoological Society of London (1878) 393–416; (1879), 553–588; (1881), 693–724, 922–952; (1882), 656–687; (1883), 88–115; (1884), 111–149, 341–372; (1885), 27–63; 5 further parts were published by E. R. Sykes in Proceedings of the Malacological Society of London, 6 (1904), 23–40; 6 (1905), 322–332; 7 (1906), 173–190; 9 (1911), 331–348 16 (1925), 181–193.

11. Secondary Literature. The most detailed obituary of Jeffreys is probably W. B. Carpenter, in “Obituary Notices of Fellows Deceased” in Proceedings of the royalsociety, 38 (1885), xiv-xviii. Numerous others are listed in the Royal Society’s Catalogue of Scientific Papers, XVI, p. 93. A most readable account of the general results of the dredging cruises of the Lightning and Porcupine is C. Wyville Thomson, The Depths of the Sea (London, 1873). The contents of jeffreys’ collections are detailed in a letter to W. H. Dall published in Smithsonian MiscellaneousCollections,104 no. 15 (1946), 9.

David Heppell

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Jeffreys, John Gwyn

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