But in spite of the ill-success of Sir Henry Grey the King in 1476 licensed David Beaupee and John Merchaunt to practise for four years 'the natural science of the generation of gold and silver from mercury.' Alchemy, indeed, was clearly flourishing in the fifteenth century. In 1468 Richard Carter received authority to practise the art, while under Henry VI. several such licences were granted. Thus in 1444 Edward Cobbe was authorised 'to transmute the imperfect metals from their own kind by the art of Philosophy and to transubstantiate them into gold or silver'; two years later Sir Edmund Trafford and Sir Thomas Ashton were empowered to transmute metals, and in 1446 John Fauceby, John Kirkeby, and John Rayny received the royal permission to search for the philosopher's stone or the elixir of life and to transmute metals. Presumably the need for royal licence in all these cases was based on the royal claim to all mines, and therefore to all other sources, of precious metals. Covetous eyes had been cast upon Alchemy as a possible source of revenue at least as early as 1330, when Thomas Cary was ordered to bring before King Edward III. John le Rous and Master William de Dalby, who were said to be able to make silver by alchemy, with the instruments and other things needful to their craft. But of all these scientists and philosophers no more is heard, and, although I have not searched the accounts of bullion purchased for the Mint, it may safely be asserted that the revenue profited little by all their science and philosophy.