John, a distinguished mathematician of the eighteenth century, the English D'Alembert, as he is called by the French, was born at Peakirk in Northamptonshire in 1719, and died in 1790. The most of his time was spent in the pursuits of active life, but he early showed strong talent for mathematical study, which he eagerly cultivated at his leisure hours. In 1762 he was appointed agent to Earl Fitzwilliam, and held that office till within two years of his death. Beyond these facts nothing is known of his private history, which seems to have been more than usually uneventful. He lived a very retired life, and saw little or nothing of society. When he did mingle in it, his dogmatism and pugnacity caused him to be generally shunned. He first made himself known as a mathematician in 1744, by his essays in the Ladies' Diary for that year. Besides his separate works, he communicated to the Royal Society at different times valuable papers on the most difficult parts of mathematical and physical science, all of them distinguished by depth and powerful ingenuity. One of the most memorable of his achievements was a new form of the fluxionary calculus, which he published in 1758, under the title of Residual Analysis. The plan proposed, though inelegant and needlessly complex, may be deemed on the whole an improvement on the method of ultimate ratios. To confer more consequence on his innovation, he contrived likewise a set of symbols and applied his algorithm to the solution of different problems; but it never attained any currency, and soon fell into oblivion.

Landen's works, not included in the Transactions of the Royal Society, are, a volume of Mathematical Lucubrations, 1755; the Residual Analysis, 1764; two volumes of Memoirs; and some tracts on Converging Series.