tempted classification upon a principle of his own represented by a system of triangles (Chemical Soc. Journal, viii. 110; Professor Maskelyne's Preface to Mansfield's Theory of Salts, pp. 23-7, where the principle is described). Next summer Mansfield, 'to gratify a whim of wishing to see the country, which I believed to be an unspoiled Arcadia' (Letters from Paraguay, Pref. p. 8), started for Paraguay. He arrived at Buenos Ayres in August, and having obtained permission from Urquiza, whom he describes as an 'English farmer-like, honest-looking man' (ib. p. 157), to go up the Parana, he reached Assumption on 24 Nov., and remained there two and a half months. Paraguay, under Francia and his successor Lopez, had been shut from the world for forty years, and Mansfield was, if not the first English visitor to the capital, certainly the first to go there merely to take notes. His letters, published after his death, contain bright and careful descriptions of Paraguayan society, 'the scenery, plant and bird life, and a scheme for the colonisation of the Gran Chaco, a favourite dream with him for the rest of his life. A sketch of the history of Paraguay, valuable for the period immediately preceding and following his arrival, forms the concluding chapter of the volume of 'Letters.' His earlier letters, printed in the same volume, deal in a similar manner with Brazil. These were translated into Portuguese by Pascual, and published along with elaborate critical essays on Mansfield's narrative at Rio Janeiro, the first volume in 1861, the second in 1862.
Mansfield returned to England in the spring of 1853, resumed his chemical studies, and began a work on the constitution of salts, based on the lectures delivered two years previously at the Royal Institution. This work, the 'Theory of Salts,' his most important contribution to theoretical chemistry, he finished in 1855, and placed in a publisher's hands. He had meanwhile been invited to send specimens of benzol to the Paris Exhibition, and on 17 Feb. 1855, while preparing these in a room which he had hired for the purpose in St. John's Wood, a naphtha still overflowed, and Mansfield, in attempting to save the premises by carrying the blazing still into the street, was so injured that nine days later he died in Middlesex Hospital. He had not completed his thirty-sixth year.
Mansfield's works, published at various intervals after his death, are fragments to which he had not added the finishing touch, yet each bears the unmistakable impress of a mind of the highest order, a constant attitude towards the sphere of knowledge more akin to that of Bacon or Leibnitz than of a modern specialist. The testimony, written or spoken, of many who knew him confirms Pascual's estimate, 'a great soul stirred by mighty conceptions and the love of mankind' (Ensaio Critico, p. 8). A portrait of Mansfield by Mr. Lowes Dickinson is in the possession of his brother, Mr. R. B. Mansfield. The engraving prefixed to the 'Letters from Paraguay' is from a photograph.
[Private information from Mr. R. B. Mansfield; Memoir by Kingsley, prefixed to Letters from Paraguay; Mrs. Kingsley's Life of Kingsley, 1877, pp. 216–18, 440–4; Preface by Professor Maskelyne to the Theory of Salts; Mr. J. M. Ludlow's Preface to Aerial Navigation; Chem. Soc. Journal, viii. 110–12; Pascual's Ensaio Critico sobre a viagem ao Brasil, 1861–2; Wurtz's Dictionnaire de Chimie, i. 527, 542–3, 545; Hofmann's Report on the Exhibition of 1862; Chemistry, p. 123; Study of Chemistry, p. 9; Timbs's Year-book of Facts, 1850, pp. 75–7; Fraser's Mag. liv. 591–601; New Quarterly Review, 1856, pp. 423–8.]
MANSFIELD, HENRY de (d. 1328), chancellor of Oxford University. [See Maunsfield.]
MANSFIELD (originally MANFIELD), Sir JAMES (1733–1821), lord chief justice of the court of common pleas, born in 1733, son of John James Manfield, attorney, of Ringwood, Hampshire, was elected a scholar of Eton in 17 730 (Harwood, Alumni Eton. v. 339), and proceeded to King's College, Cambridge, where he obtained a fellowship in 1764, graduated B. A. in 1765 and M.A. in 1758 (Grad. Cantabr.) His grandfather is said to have been a foreigner, and to have held some post in Windsor Castle. Mansfield inserted the s in his name while still at Cambridge. In November 1758 he was called to the bar at the Middle Temple. He practised both at common law and in chancery, and was engaged in some state trials. He was one of Wilkes's advisers on his return to England in 1768, and argued in support of his unsuccessful application in the king's bench to be admitted to bail for the purpose of prosecuting a writ of error against his outlawry (20 April). He took silk in July 1772, and was afterwards appointed counsel to the university of Cambridge. Another of Mansfield's clients was the bigamous Duchess of Kingston, whose immunity from punishment he materially contributed to secure in 1776. The same year he appeared for the defence in the Hindon bribery case, the year following for the incendiary, James Aitkin [q. v.], and in 1779 for the crown (with Attorney-general Wedderburn [q. v.]), on the information exhibited against George Stratton