Dr Thomas, an eminent historical and biographical writer, was born in London in 1705. His parents were both of them Quakers; and his father, Joseph Birch, was a coffee-mill maker by trade. Thomas being put to school, was indefatigable in his application, and stole many hours from sleep to increase his stock of knowledge. By this unremitting diligence, though he had not the happiness of an university education, he soon became qualified to take holy orders in the church of England, to the surprise of his acquaintance. In 1728 he married the daughter of the Rev. Mr Cox, to whom he was curate: but his felicity was of short duration, Mrs Birch dying of a puerperal fever in less than 12 months after their marriage; an event which he deplores in a very elegant and pathetic poem, preserved in Nichols's Collection. In 1732 he was recommended to the friendship and favour of the late lord high chancellor Hardwicke, then attorney general; to which noble peer, and to the present earl of Hardwicke, he was indebted for all his preferments. The first proof he experienced of his patron's regard was the living of Ulting in the county of Essex, in the gift of the crown, to which he was presented 1732. In 1734 he was appointed one of the domestic chaplains to the unfortunate earl of Kilmaineock, who was beheaded in 1746. Mr Birch was chosen a member of the Royal Society, Feb. 20, 1734-5; and of the Society of Antiquaries, Dec. 11, 1735, of which he afterwards became director till his death. Before this, the Marischal college of Aberdeen had conferred on him, by diploma, the degree of master of arts. In 1743, by the interest of Lord Hardwicke, he was presented by the crown to the finecurate rectory of Landewy Welfrey in the county of Pembroke; and in 1743-4 was preferred, in the same manner, to the rectory of Sidington in St Peter's, in the county and diocese of Gloucester. We find no traces of his having taken possession of this living; and indeed it is probable that he quitted it immediately for one more suitable to his inclinations and to his literary engagements, which required his almost constant residence in town; for on the 24th of February 1743-4, he was instituted to the united rectories of St Michael Woodstreet, and St Mary Staining; and in 1745-6, to the united rectories of St Margaret Pattens and St Gabriel, Fenchurch-street (by lord chancellor Hardwicke, in whose turn the presentation then was). In January 1752, he was elected one of the secretaries of the Royal Society, in the room of Dr Cromwell Mortimer, deceased. In January 1753, the Marischal college of Aberdeen created him doctor of divinity; and in that year the same degree was conferred on him by Archbishop Herling. He was one of the trustees of the British Museum; for which honour he was probably indebted to the present earl of Hardwicke, as he was for his last preferment, the rectory of Depden in Essex, to which he was inducted Feb. 26, 1761. In the latter part of his life he was chaplain to the Prince's Amelia. In 1765 he resigned his office of secretary to the Royal Society, and was succeeded by Dr Morton. His health declining about this time, he was ordered to ride for the recovery of it; but being a bad horseman, and going out Jan. 9, 1766, he was unfortunately thrown from his horse, on the road betwixt London and Hampstead, and died on the spot, in the 61st year of his age, to the great regret of the doctor's numerous numerous literary friends; and was buried in St Margaret Pattens. Dr Birch had in his lifetime been very generous to his relations; and none that were nearly allied to him being living at his decease, he bequeathed his library of books and manuscripts, with his picture painted in 1735, and all his other pictures and prints not otherwise disposed of by his will, to the British Museum. He likewise left the remainder of his fortune, which amounted to not much more than 300l. to be laid out in government-securities, for the purpose of applying the interest to increase the stipend of the three assistant librarians; thus manifesting at his death, as he had done during his whole life, his respect for literature, and his desire to promote useful knowledge. To the Royal Society he bequeathed his picture painted by Wills in 1737, being the original of the mezzotinto print done by Fauber in 1741. His principal publications were, 1. The General Dictionary, Historical and Critical; including a new translation of Mr Bayle, and interpered with several thousand new lives. Dr Birch's associates in this undertaking were, the Reverend John Peter Bernard, Mr John Lockman, and Mr George Sale. The whole design was completed in 10 volumes folio. 2. Dr Cudworth's Intellectual System (improved from the Latin edition of Molheim), his Discourse on the true Notion of the Lord's Supper, and two Sermons, with an account of his Life and Writings, 2 vols. 4to, 1743. 3. The Life of the Hon. Robert Boyle, 1744; prefixed to an edition of that excellent philosopher's works, revised by Dr Birch. 4. The Lives of Illustrious Persons of Great Britain, annexed to the engravings of Houbenken and Vertue, 1747-1752. 5. An Inquiry into the Share which King Charles I. had in the Transactions of the earl of Glamorgan, 1747, 8vo. 6. An edition of Spenser's Fairy Queen, 1751, 3 vols. quarto, with prints from designs by Kent. 7. The Miscellaneous Works of Sir Walter Raleigh; to which was prefixed the Life of that great, unfortunate, and injured man, 1751, 2 vols. 8vo. 8. The Theological, Moral, Dramatic, and Poetical Works of Mrs Catharine Cockburn; with an Account of the Life of that very ingenious Lady, 1751, 2 vols. 8vo. 9. The Life of the Most Reverend Dr John Tillotson, Lord Archbishop of Canterbury. Compiled chiefly from his original Papers and Letters, 1752, 8vo. 10. Milton's Prose Works, 1753, 2 vols. 4to; with a New Life of that great poet and writer. 11. Memoirs of the Reign of Queen Elizabeth, from the year 1581 till her death. In which the secret intrigues of her court, and the conduct of her favourite Robert earl of Essex, both at home and abroad, are particularly illustrated. From the original papers of his intimate friend Anthony Bacon, Esq.; and other manuscripts never before published, 1754, 2 vols. 4to. 12. The History of the Royal Society of London for improving natural knowledge, from its first rise. In which the most considerable of those papers communicated to the Society, which have hitherto not been published, are inserted in their proper order as a supplement to the Philosophical Transactions, 1756 and 1757, 4 vols. 4to. 13. The Life of Henry Prince of Wales, eldest Son of King James I. Compiled chiefly from his own papers and other manuscripts, never before published, 1760, 8vo. His numerous communications to the Royal Society may be seen in the Philosophical Transactions; and his poetical talents are evident from the verses already referred to.