The execution of women for witchcraft was generally by hanging, but Bristol had a brutal reputation for punishment, especially of gay men, so it is not too surprising that women were being burnt to death in the 18th century. This comes from John Latimer’s Annals of Bristol :
as the result of a gaol delivery, murderers and the worst class of thieves were compelled to walk to the gallows on St Michael’s Hill to suffer death. These executions were frighteningly numerous; on two occasions within the space of twenty years five unhappy creatures were hanged in a batch. For various crimes the punishment of women was death by burning. On the 15th of June, 1695, … a woman, a shopkeeper in Temple Street, was burnt for coin clipping, [though another source claims] she escaped fro Newgate before the day fixed for her execution. A girl of fourteen years, for murdering hr mistress, was burnt in London in 1712. A woman who had murdered her husband, suffered at Gloucester in 1753; another for the same crime perished in Somerset in 1765; and a girl, 18 years old, for murdering her mistress, underwent the same fate at Monmouth in 1764. The witches remain to be mentioned. There were few Bristolians who were not in dread of them, and such apprehensions were common, amongst cultivated Englishmen. The contemporary Bishop of Gloucester… avowed his belief not merely in witches, but in fairies; and John Wesley, long after this date, declared that non-believers in witchcraft were little better then infidels. In 1683 3 women were hanged at Exeter for witchcraft. A wizard was tried about the same time at Taunton, and was rescued from death only by the sceptical ingenuity of the judge, Lord Guilford. In 1701… a woman narrowly escaped conviction as a witch in London, the prosecutor’s perjury being discovered, apparently in court. I 1702 a so-called witch perished in Edinburgh, … and 2 more women were executed at Northampton in 1705. In or about the latter year a man named Silvester in Bristol, fell under such deep suspicion of unholy arts that he prudently disappeared before his neighbours could take action. … so late as 1730 at Frome, a poor old woman, suspected of being a witch, was, by the advice of a “cunning man” thrown into a pool and drowned by 20 of her neighbours, in the presence of 200 persons, who made no attempt to save her life.