With Coke and many others; documentary records of various courts are exemplified in the Select Cases from the star chamber, the court of requests and admiralty courts, published by the Selden Society; and there are voluminous records of the courts of augmentations, first-fruits, wards and liveries in the Record Office.
According to Aubrey, Selden left him an equal bequest, but this seems to be a mistake.
It was not till many years afterwards that the jealousies between England and Holland gave importance to the novel doctrine broached in the tract by Grotius, a doctrine which Selden set himself to refute in his Mare clausum (1632).
He founded or endowed various professorships, including those of Hebrew and Arabic, and the office of public orator, encouraged English and foreign scholars, such as Voss, Selden and Jeremy Taylor, founded the university printing press, procuring in 1633 the royal patent for Oxford, and obtained for the Bodleian library over 1300 MSS., adding a new wing to the building to contain his gifts.
He edited numerous volumes for the Selden Society, including Select Pleas for the Crown, 1200-1225, Select Pleas in Manorial Courts and The Court Baron; and among his principal works were Gloucester Pleas (1884), Justice and Police (1885), Bracton's Note-Book (1887), History of English Law (with Sir F.
Maitland, Select Pleas in Manorial Courts, Selden Soc. Publications I.
In Mare clausum (1635) John Selden endeavoured to prove that the sea was practically as capable of appropriation as territory.