See the Lives in the Dictionary of National Biography and in Biographia Britannica (Kippis), with authorities there collected; Essex's Irish correspondence is in the Stow Collection in the British Library, Nos. 200–217, and selections have been published in Letters written by Arthur Capel, Earl of Essex (1770) and in the Essex Papers (Camden Society, 1890), to which can now be added the Calendars of State Papers, Domestic, which contain a large number of his letters and which strongly support the opinion of his contemporaries concerning his unselfish patriotism and industry; see also Somers Tracts (1815).