[1] He was admitted to Westminster School on Bishop Williams's foundation, and thereafter entered Christ Church, Oxford.
He was one of the preachers at Whitehall, chaplain to the bishops of Worcester and Winchester, rector of Droxford, Hampshire, and vicar of Lathbury, Buckinghamshire.
[1] Chelsum, in ‘Remarks on the two last chapters of Mr. Gibbon's “History of the Decline and Fall of the Roman Empire,” in a letter to a friend’ (1776, published first anonymously, but afterwards enlarged and acknowledged, Oxford, 1778), attacked the account given of the growth of the Christian church by Edward Gibbon in The History of the Decline and Fall of the Roman Empire.
Gibbon replied in a ‘Vindication' (1779), in which he admitted that the "zeal of the confederate doctors is enlightened by some rays of knowledge" but sneers "at the rustic cudgel of the staunch and sturdy Polemics," (pp.
Chelsum answered this in ‘A Reply to Mr. Gibbon's Vindication’ (Winchester, 1785), in which he adduces fresh arguments in support of his position, and asserts that he conducted the discussion with candour and moderation.