**Bevan Braithwaite Baker**'s father was George Samuel Baker (born in Canada about 1861) who was a bread and biscuit machinery engineer and manufacturer. His mother was Martha Braithwaite (born at St Pancras, Middlesex about 1853). Bevan Baker had two older siblings: Sarah (born about 1888) and George ( born about 1889).

Bevan Braithwaite Baker was always known as Bevan Baker but only after he retired did he begin to use Bevan-Baker as a surname. Bevan was born into a Quaker family with both his parents having Quaker backgrounds. His father was George Samuel Baker from Willesden.

Baker attended Sidcot School in Somerset before entering University College, London, to study physics. After graduating with a physics degree, Baker went to Munich to undertake research but quickly decided that his love was mathematics rather than physics so he returned to University College, London to take an Honours Mathematics degree.

During World War I he served with the Friends Ambulance Unit in Italy, then after ending his war service he taught for a short time at University College, London before being appointed as a Lecturer in Mathematics at Edinburgh University in 1920. He had married Margaret Stewart Barbour in Edinburgh in 1918; they had five children, three girls and two boys. In 1924 Baker left Edinburgh when he was appointed Professor of Mathematics in Royal Holloway College, University of London. He taught there until 1944 when, although only 54 years old, he was forced to retire through ill health.

Baker was a member of the Edinburgh Mathematical Society, joining in December 1920. In 1921 he cooperated with E B Ross in an important paper *On the Vibrations of a Particle about a Position of Equilibrium* in which they explained the long-noted phenomenon of the great difference between the orbit of Jupiter and that of Saturn.

Baker served the Society as Secretary from 1921 until he left Edinburgh in 1924. He contributed papers to the meetings, for example on Friday 10 November 1922 he read *The Vibrations of a Particle about a Position of Equilibrium, Part 3* to a meeting of the Society.

Bevan Baker was elected to the Royal Society of Edinburgh on 7 March 1921, his proposers being Sir Edmund T Whittaker, Cargill G Knott, Ellice M Horsburgh, Alexander H Freeland Barbour.

An obituary, written by E T Copson, appears in the Royal Society of Edinburgh Year Book 1964, pages 7-8.

We give a version of this obituary at THIS LINK.

In 1939 Bevan-Baker published the book *The Mathematical Theory of Huygens' Principle* in collaboration with E T Copson. The book was reviewed by Bateman who wrote:-

A second edition of the book, which differed from the first by the addition of a new chapter on the application of the theory of integral equations to problems of diffraction theory by a plane screen, was published in 1950. A third edition, with some minor improvements, was published in 1987.Huygens' geometrical construction, with its restriction that only one sheet of the envelope of the spherical wavelets is to be considered, is first justified in Chapter I by Poisson's analytical solution of the equation of wave-motions. A discussion is then given of the ideas of Fresnel and of the formula of Helmholtz which expresses these ideas in analytical form and gives the principle of Huygens for periodic processes. The diffraction formulae of Fresnel and Stokes are then obtained.Kirchhoff's famous formula is first derived from the formula of Helmholtz and then proved directly. The formula is interpreted physically and the question of the uniqueness of the solution discussed. It is pointed out that to extend the theorem of Kirchhoff to the space outside a closed surface it is necessary to prescribe the asymptotic behaviour of the wave-functions under consideration. The peculiarities of wave-propagation in two dimensions are next indicated and Weber's analogue of Helmholtz's theorem is given. The analogue of Kirchhoff's formula, due to Volterra, is derived and an interesting account is given of a method, devised by Marcel Riesz and based on the theory of fractional integration, which provides a powerful method of solving initial value problems for equations like the wave equation.

The rest of the book is devoted chiefly to the problem of diffraction. Part of Chapter II includes a useful discussion of an important type of definite integral which occurs in the analysis of diffraction problems. Diffraction by a black screen is discussed in some detail. In Chapter III Huygens' principle is formulated for electromagnetic waves and Tedone's proof is given for some formulae which are associated with the names of Larmor and Tedone. Chapter IV contains a good account of Sommerfeld's theory of diffraction.

Finally let us give some details of John Stewart Bevan Baker, the youngest of Bevan and Margaret Baker's children. John was born in Staines, Middlesex, on 3 May 1926. He had a natural talent for art, music, English and mathematics. From Preparatory school at The Downs in Colwall, England, he proceeded in 1939 on an Art Scholarship to Blundells School in Devon. Completing his studies in 1944, his pacifist disposition (coming from his Quaker family background) took him down Newbiggin coalmine in Northumberland as a Bevin Boy between 1944 and 1946, thus fulfilling his war service. Then in 1946 he entered the Royal College of Music to study organ and music composition.

**Article by:** *J J O'Connor* and *E F Robertson*

**Click on this link to see a list of the Glossary entries for this page**