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 are of special importance: Fountains Abbey (1900); The Architectural History of the Cathedral Church of St. Andrew at Rochester (1900); The Stall-Plates of the Knights of the Order of the Garter (1901); The Abbey of St. Mary-in-Furness (1902); Windsor Castle, an architectural history, 2 vols., with portfolio of plans (1913); A Grammar of English Heraldry (1913); Heraldry for Craftsmen and Designers (1913); Cowdray and Easebourne Priory (1919); The History of the London Charterhouse (1925). He was also a principal collaborator in The Chronicles of … All Saints, Derby (with J. C. Cox, 1881); The Corporation Plate … of the Cities of England and Wales (completed from the work of Llewellynn Frederick William Jewitt [q.v.], 1895); Inventories of Christ Church, Canterbury (with J. Wickham Legg [q.v.], 1902); Kirkstall Abbey (with J. Bilson, 1907); Pageant of the Birth, Life and Death of Richard Beauchamp, Earl of Warwick (with Viscount Dillon, 1914); English Liturgical Colours (with E. G. C. F. Atchley, 1918).

 HOPKINSON, BERTRAM (1874–1918), engineer and physicist, was born at Birmingham 11 January 1874. He was the eldest son of Dr. John Hopkinson, F.R.S. [q.v.], by his wife, Evelyn Oldenbourg, and inherited his father's combination of mathematical power with insight into physics, and with the ability to apply scientific ideas to practical problems. The family soon moved to London, and Bertram was educated at St. Paul's School, living at home in close association with his father, from whom he imbibed scientific habits of thought as well as much engineering knowledge. At the age of seventeen he went to Cambridge, entering Trinity College with a major scholarship. He missed the first part of the mathematical tripos through illness; in the final part he was placed in the first division of the first class. Soon after taking his degree (1895) he was called to the bar, but the tragic death of John Hopkinson in 1898 led Bertram to turn to engineering, in order to continue, so far as he could, his father's unfinished professional work. By 1903 he had acquired a considerable reputation as an engineer, and when, in that year, the chair of mechanism and applied mechanics at Cambridge became vacant, Hopkinson was selected to fill it. He held the professorship until his death fifteen years later. In 1903 he married Mariana, eldest daughter of Alexander Siemens, a former president of the Institution of Civil Engineers, and by her he had seven daughters.

As professor of mechanism, Hopkinson became responsible for the school of engineering at Cambridge, which, thanks to the establishment ten years earlier of a mechanical science tripos, was already vigorous. Under his management its progress was maintained, its numbers were doubled, and its position advanced both in the university and in the profession outside. Hopkinson was an effective teacher, with a passion for research which students found inspiring. A collected volume of his scientific papers, published by the Cambridge University Press in 1921, contains twenty-nine items and gives evidence of unflagging industry, originality of outlook, and ingenuity in devising methods of experiment. His chief investigations relate to the endurance of metals under varying stresses, the magnetic properties of iron and its alloys, the action of internal-combustion engines and the process of explosion in gases, and the pressure produced in the detonation of high explosives. His work is characterized by clear appreciation of practical issues, and by direct attack on the essential features of the problem in hand. He was elected F.R.S. in 1910 and became a professorial fellow of King's College, Cambridge, early in 1914.

On the outbreak of war in 1914, Hopkinson accepted a commission in the Royal Engineers. Use was soon found for his powers of experiment and design. In particular he was able to apply his previous study of explosions to the improvement of methods of attack and defence. His ‘pressure bar’ became a standard appliance for testing at Woolwich. His investigations determined the best form of bomb; other experiments, which he carried out for the Admiralty, led to the adoption of his invention for protecting ships of war by means of a projection or ‘blister’, so constructed as to absorb the energy of an exploding torpedo or mine without damage to the inner shell. For a time he was secretary of a committee set up by the Royal Society to advise the government on the scientific problems of the War, and he also took part in an organization for dealing with enemy cipher. Later he was appointed to the department of military aeronautics, where he was soon entrusted with the supply to aircraft of all items of 268