This valuable historical and biographical writer was born in the parish of St. John, Clerkenwell, on the 23rd of November, 1705. His parents were both of them Quakers; and his father, Joseph Birch, was a coffee mill-maker by trade. Mr. Joseph Birch endeavoured to bring up his son to his own business; but so ardent was the youth's passion for reading, that he solicited his father to be indulged in this inclination, promising, in that case, to provide for himself. The first school he went to was at Hemel-Hemsted in Hertfordshire. It was kept by John Owen, a rigid Quaker, for whom Mr. Birch afterwards officiated some little while as an usher. The next school was kept by one Welby, near Turnmill-street, Clerkenwell, who never had above eight or ten scholars at a time, whom he professed to instruct in the Latin tongue in a year and a half. To him Mr. Birch was, likewise, an usher; as he also afterwards was to Mr. Besse, the famous Quaker, in George's Court in St. John's Lane, who published the posthumous works of Claridge. It is farther said that he went to Ireland with Dean Smedley; but in what year, and how long he resided with the Dean, cannot now be ascertained. Smedley published in 1728 A Specimen of an universal View of all the Eminent Writers on the Holy Scriptures; being a Collection of the dissertations, explications, and opinions of learned men, in all ages, concerning the difficult passages and obscure texts of the Bible; and of whatsoever is to be met with, in profane authors, which may contribute to towards the better understanding of them. This extensive undertaking was intended to have been comprised in two large folio volumes: had the plan proceeded, it is no very far-fetched conjecture to suppose that Mr. Birch was to have been an assistant. He was indefatigable in his application, and stole many hours from sleep to increase his stock of knowledge. By his unremitting diligence, though he had not the happiness of a university education, he soon became qualified to take holy orders in the church of England, to the surprize of his acquaintance. It is not precisely known when this event took place; but it must have been as early as 1728. In the same year he married the daughter of the Rev. Mr. Cox, to whom he was curate; and in this union he was singularly happy: but his felicity was of short duration, Mrs. Birch dying in less than twelve months after their marriage. The disorder which carried her off was a puerperal fever, and almost in the very article of death she wrote to her husband the following letter: July 31, 1729. "This day I return you, my dearest life, my sincere, hearty thanks, for every favour bestowed on your most faithful and obedient wife, Hannah Birch."
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 in 1732. In 1734, he was appointed one of the domestic chaplains to the unfortunate Earl of Kilmarnock, who was beheaded 1746. Mr. Birch was chosen a member of the Royal Society, Feb. 20, 1734-35; and of the Society of Antiquaries, Dec. 11, 1735, of which he afterwards became Director till the year 1746. 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 sinecure rectory of Landewy Welfrey in the county of Pembroke; and in 1743-44 was preferred, in the same manner, to the rectory of Siddington St. Peter's, in the country 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, 1743-44, he was instituted to the united rectories of St. Michael, Wood-street, and St. Mary Staining; and in 1745-46 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 Herring. 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 Princess Amelia. In 1765 he resigned his office of Secretary to the Royal Society. 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 literary friends; and was buried in St. Margaret Pattens. A list of his valuable publications may be seen in the new edition of the Biographia Britannica.