Sidney attended school, first the Maidstone Grammar School, in Maidstone, Kent, and then, from 1874, Tonbridge School in Tonbridge, Kent, where he was taught by Henry Hilary described in  as:-
... one of the most remarkable mathematics teachers of his generation.Henry Hilary was the Senior Mathematical Master at Tonbridge School for 37 years, from 1870 to 1907. He became famous for the large number of his pupils who went on to become high Wranglers in the Mathematical Tripos at the University of Cambridge. Tonbridge School, founded in 1553, gave Loney an exceptionally high quality education. He was one of about 200 boys at the school when he began his studies. Loney was in the Sixth Form at Tonbridge School 1876-8, and during that year was Head Boy of the School. He won a Smythe Exhibition to support his studies at the University of Cambridge.
Loney was admitted to Sidney Sussex College, University of Cambridge, as a pensioner on 11 October 1878. He studied the Mathematical Tripos and graduated as 3rd Wrangler in 1882. He was a fellow of Sidney Sussex College from 1885 to 1891. E C Higgins writes :-
On leaving Sidney Sussex College, Cambridge, Loney was faced with the choice which so often confronts the ablest young graduates - the choice between the advancement of specialised learning by research, or the advancement and diffusion of sound knowledge by direct teaching. His exceptional gifts of clear exposition and fertility of illustration led him towards teaching, and he devoted himself wholeheartedly to his chosen profession, as professor of mathematics at Royal Holloway College, London. Before the establishment of the internal side of the University of London, many students of Holloway College took the Final Honours Schools of the University of Oxford, and the mathematical class lists of the years 1891-1907 afford evidence of the high standard of mathematics at the College at that time. After the College became one of the internal colleges of the University of London, a corresponding high standard was maintained in the london honours lists ...Loney was awarded a B.A. by the University of London in 1884. In July 1885 he married Frances Elizabeth Hamlin (1851-1934) who was the daughter of Hubert Palmer Osborne Hamlin (1824-1903) and Mary Ann Campbell (1821-1894). Frances Hamlin, born in Cripplegate, Middlesex, was the eldest of her parents six children having siblings Alfred Hamlin, Frederick Hamlin, Louisa Hamlin, Clarence Hamlin and Hubert A Hamlin. Sidney and Frances Loney had two daughters, Hilda Mary Luxton Loney (1886-1940) and Dorothy Frances Loney (1888-1974). Hilda, born July 1886, was baptised on 22 December 1886 and at that time the family were living at 34 Hogarth Road, St Jude, South Kensington. Dorothy, born 10 February 1888, married Harold Lister Woodhouse, who became a Colonel in the Army, in St Mary Magdalene with St Mathias Church in Richmond on 23 April 1921.
Let us return to describing Loney's career as Professor of Mathematics at Royal Holloway College. He is best known to mathematicians as the author of a series of very popular books. These include: The Elements of Statics and Dynamics, Part I Statics (1890); The Elements of Statics and Dynamics. Part II Dynamics (1891); Mechanics and Hydrostatics for Beginners (1892); Plane trigonometry (1893); The Elements of Coordinate Geometry (1895); The Elements of Hydrostatics (1901); Shilling Arithmetic (1906); An Elementary Treatise on the Dynamics of a Particle and of Rigid Bodies (1909); Solutions of the Examples in a Treatise on Dynamics of a Particle and of Rigid Bodies (1909); An Elementary Treatise on Statics (1912); The Elements of Coordinate Geometry. Part II. Trilinear Coordinates (1923).
For a version of Loney's Prefaces to some of these books, see THIS LINK.
For reviews of some of these books, some of which are quite critical, see THIS LINK.
For extracts from reviews of Loney's books which Cambridge University Press used in advertising, see THIS LINK.
Harold Simpson writes :-
As a teacher he had extraordinary success, and he could teach in print with the same facility as in the lecture room. His textbooks on mechanics, coordinate geometry, and trigonometry evidently supplied the needs of the student, for they became household words and the "best sellers" of the mathematical market. They excelled in their collections of "exercises", of a type which is perhaps a little too artificial (planes always inclined at 30° to the horizon when it isn't 45° or 60°, and particles describing central orbits under weird laws of force), but attractive in their variety and the neatness of their answers.In addition to his teaching and writing textbooks, Loney did an excellent job for the University of London. E C Higgins writes :-
Loney was an excellent man of business, with a genius for committee work; and for many years he was one of the most influential members of the Senate of the University of London. His capacity for strenuous work, his thorough grasp of business, and his intuitive knowledge of man and women, were given full scope during the Great War (1914-18), when for a considerable time he carried out many of the duties of Principal Officer of the University in addition to his other work.In 1920 Loney retired from his position as Professor of Mathematics at Royal Holloway College but he continued to undertake work for the University as well as serving the local community. He was a Justice of the Peace for Richmond and served as Mayor of Richmond, Surrey, during 1920-21. He served as Chairman of Convocation, University of London, from 1923 and as Deputy Chairman of the Court from 1929 :-
These services were all the more valuable because of his dual position in the University. As a former professor in one of the internal colleges, he was a warm supporter of the teaching side; on the other hand, he was also an active and enthusiastic representative of the external side; and he was strongly of the opinion that there was ample room for both internal and external sides in a great Imperial university, and that harmonious cooperation was the desirable ideal.Loney's wife, Frances Elizabeth Loney, died on 30 November 1934, leaving £908 to her husband Sidney Luxton Loney in her will. He died in May 1938 at Richmond and was buried there. In his will he left £81,316 to:-
Hilda Mary Luxton Loney, spinster; Harold Lister Woodhouse Colonel H.M. army; and Percy Ernest Loney, retired bank manager.These were, respectively, his unmarried daughter, the husband of his married daughter, and one of his surviving brothers. The sum of £81,316 was massive in 1939, being the equivalent of about £5,000,000 in today's money. This large sum must show how financially successful his many textbooks proved to be.
Article by: J J O'Connor and E F Robertson