Born: 1 June 1907, Ireland
Died: 26 February 2002
Country most active: United Kingdom
Also known as: NA
This biography is republished from The Dictionary of Irish Biography and was written by J.M.D. Coey. Shared by permission in line with Creative Commons ‘Attribution’ (CC BY) licencing.
Megaw, Helen Dick (1907–2002), crystallographer, was born on 1 June 1907 at 44 Northumberland Road, Dublin, the eldest child and one of five daughters and two sons (along with Thomas and Alice (twins), John, Margaret, Annie and Sarah) of Robert Megaw, a lawyer and professor of common law at King’s Inns, Dublin, and Annie McElderry, a mathematics teacher at the Rutland School, Dublin. Robert Megaw, a member of the Orange Order, became a king’s counsel (KC) and served a term (1921–5) as a member of the Northern Ireland parliament for Antrim. His was a family of high achievers, and he had high expectations for his children.
Helen Megaw was educated at Alexandra College, Dublin, from 1916 to 1921, when the family moved to Belfast, where she continued her education at Methodist College before being sent to Roedean School, near Brighton. There she first read W. H. and W. L. Bragg’s X-rays and crystal structure (1915). She matriculated at Queen’s University Belfast (QUB) before winning a Todd memorial scholarship that allowed her to move to Girton College, Cambridge, to read chemistry, physics and mineralogy for the natural sciences tripos. On graduating in 1930, she began postgraduate work at the Cavendish Laboratory, Cambridge, with the Irish polymath Desmond Bernal, himself a student of W. H. Bragg. Bernal led a group devoted to groundbreaking uses of X-ray diffraction to investigate the structures of crystalline, amorphous and molecular matter, the understanding of which became the key to some of the most important advances in twentieth-century science. Megaw’s colleagues and friends in Bernal’s group included Dorothy Hodgkin, who became the first British woman to win a Nobel prize, for determining the structure of vitamin B12.
Crystallography at Cambridge was a rare area of research where men and women contributed on an equal basis. Megaw used X-rays to study thermal expansion and determined the crystal structure of hydrargillite (gibbsite), an aluminium hydroxide. She grew ice crystals from both normal and heavy water using an original method that involved encapsulating the water in a thin-walled glass tube and cycling temperature around the freezing point. Megaw and Bernal inferred that there were two types of hydrogen bonds, one where the hydrogen was close to oxygen (as in hydroxides), the other where it oscillates between two positions between a pair of oxygens (as in water). Megaw’s method was also used by British chemist Rosalind Franklin to grow crystals of DNA in a mother liquor.
In 1934, having been awarded a doctorate from Cambridge, Megaw spent a postdoctoral year with Austrian-American chemist Herman Mark at the University of Vienna, followed by a year with physical chemist Francis Simon at the Clarendon Laboratory in Oxford, before becoming a schoolteacher in 1936 at Bedford High School and then at Bradford Girls Grammar School. In 1943, she accepted an invitation to join Philips Lamps Ltd in Mitcham, Surrey, for classified research on barium titanate (BaTiO3), a recently discovered ferroelectric ceramic that had important potential applications. She determined its tetragonal perovskite-type crystal structure and showed that ferroelectricity disappeared when the structure became cubic at a phase transition above room temperature. Her name is permanently associated with barium titanate, which later became the mainstay of a multibillion-dollar industry. After the second world war, in 1945, she joined Bernal at Birkbeck College, London, where he had been appointed professor of physics. The following year, however, Megaw became a fellow (and later a life fellow) of Girton College. She resumed work at the Cavendish Laboratory as associate director of crystallography and eventually became a lecturer in physics in 1959. For the Festival of Britain, the great forward-looking exhibition organised on the south bank of the Thames in 1951, Megaw served as scientific consultant to the exhibition’s festival pattern group. The group co-ordinated contributions from various industries that promoted products featuring crystal structure diagrams sourced from Megaw and the pattern group, as did the furnishings and tableware in the festival’s Regatta restaurant.
Megaw’s interests in crystallography were centred on two of the large families of inorganic oxide minerals related to perovskite and feldspar; their crystal structures include periodic arrays of octahedra or tetrahedra of oxygen anions which share corners or edges, and each contain a metal cation. Megaw had the remarkable gift of being able to visualise these structures in three dimensions from any angle, and could see how small tilts or twists of the linked oxygen units propagated throughout the structure and determined its spatial symmetry. Together with her skill at collecting and analysing the X-ray diffraction patterns recorded on special photographic film (with no aid from digital computers), she succeeded in establishing a body of precise information on oxide minerals which has had a durable impact on earth science. Feldspars are the major constituent of the Earth’s crust, but under the enormous pressures and temperatures prevailing in the Earth’s mantle, dense oxide minerals with the perovskite structure are ubiquitous, and they are now believed to account for most of the volume of the Earth.
Megaw authored numerous influential books and journal articles, published inter alia in Nature, Proceedings of the Physical Society and Proceedings of the Royal Society, as well as Ferroelectricity in crystals (1957) and Crystal structures: a working approach (1973). She was the first woman and fifty-second recipient, in 1989, of the Roebling medal, the highest honour awarded by the Mineralogical Society of America. Megaw Island in Antarctica is named in her honour, as is the orthorhombic perovskite mineral Megawite (CaSnO3). She was awarded a doctorate in science (D.Sc.) by Cambridge University in 1967, and an honorary doctorate by QUB in 2000. The citation for the latter, delivered by Ruth Lynden-Bell, recalled that Megaw was one of a number of women attracted to the newly emerged field of X-ray crystallography: ‘In those pioneering days preparation of crystals and collection of data was more difficult and more skilled than it is today … there were no computers and the detailed calculations which lead from the brightness of spots on a photographic plate to a three-dimensional crystal structure were all done by hand. Dr Megaw was one of the pioneers in this field’ (Lynden-Bell).
After her retirement in 1972, Megaw moved to the family home in Ballycastle, Co. Antrim, where she lived with her sister. She maintained a passion for crystallography and was often seen back in Cambridge. Megaw never married, believing the life of a professional scientist to be incompatible with the role of wife and mother. She was kind and generous with her time, especially with students, on one occasion assisting one of her former postdoctoral researchers, Mike Glazer, in revising an article after it received severe criticism from a peer reviewer; some years later she revealed that she had been the peer reviewer. Megaw was resolute in her scientific and political opinions, which were at odds with those of many of her colleagues in Bernal’s group. She was a lifelong and enthusiastic amateur botanist.
Helen Megaw died of a stroke on 26 February 2002 at 22 Dunamallaght Road, Ballycastle, Co. Antrim. Her personal papers and research notes are deposited in the Girton College archive, while the Victoria and Albert Museum also holds a collection of her papers, largely related to her work with the Festival of Britain.