For fourteen years he devoted himself largely to compiling a new English-French and French-English
dictionary. It appeared in 1846 as
General English and French Dictionary, newly composed from the English dictionaries of Johnson, Webster, Richardson, &c., and from the French dictionaries of the French Academy, of Laveaux, Boiste, (London, 1846). It proved superior to anything which had preceded it, and was at once ‘autorisé par le conseil de l'instruction publique’, 3 July 1846. The twenty-ninth edition, in two volumes, appeared in 1884 (remodelled by H. Witcomb, Spiers's successor at the École des Ponts et Chaussées), and it remained for a long time a standard dictionary. Both
Ralph Waldo Emerson and
John Muir owned copies. An abridgment, under the title of
Dictionnaire abrégé Anglais-Français et Français-Anglais, abrégé du Dictionnaire Général de M. Spiers, was brought out in 1851 and supplied to almost every school and lycée in France. In November 1857 he brought an action against
Léon Contanseau and his publishers,
Longmans & Co., for violating the copyright of his dictionaries in a work entitled
A Practical Dictionary of the French and English Languages’ but Vice-chancellor Sir
William Page Wood (afterwards Lord Hatherley), in his decision on 25 February 1858, said that, although great use of Spiers's books had been made without due acknowledgement, yet in regard to such publications, which were not entirely original, a charge of piracy could not be sustained.
Major General Sir Edward Louis Spears, 1st Baronet (1886–1974) was his grandson, who had changed his name from Spiers to Spears. ==Works==