“John Wilkinson and his father Isaac played no unimportant part in the vast industrial movement of their time. Isaac invented and first brought into action the steam-engine blast at his iron works near Wrexham. John, at the same place, as also at Bradley Forge, in Staffordshire, executed all the ponderous castings for the steam engines required in the Cornish mines, as well as those for Boulton and Watt when they first commenced business.” The father was ruined in one of the commercial crises of which the times were fertile. Of the son we shall hear more as this history proceeds. He was one of the truest and staunchest of the many true and staunch friends Priestley possessed.[9] Priestley was married in 1762, Mr Threlkeld, one of the students at the academy, who subsequently became a well-known Presbyterian divine, notable for his linguistic attainments and his extraordinary power of memory, being his groomsman. Whatever might be Mr Threlkeld’s faculty of recollection it went wholly astray on this occasion, for he became so absorbed in the study of a Welsh Bible he found beside him in the pew that he became quite oblivious to the onerous duties of his office. Of his marriage Priestley characteristically writes:— “This proved a very suitable and happy connection, my wife being a woman of an excellent understanding, much improved by reading, of great fortitude and strength of mind, and of a temper in the highest degree affectionate and generous; feeling strongly for others, and little for herself. Also, greatly excelling in everything relating to household affairs, she entirely relieved me of all concern of that kind, which allowed me to give all my time to the prosecution of my studies and the other duties of my station.” All accounts we have of Mary Wilkinson are to the same effect. Her great-granddaughter, Madame Belloc, writes:— “It is a tradition in the family that Mrs Priestley once sent her famous husband to market with a large basket, and that he so acquitted himself that she never sent him again! Mrs Priestley was extremely intelligent and original. Lord Shelburne once found her sitting on the top of a pair of steps, clad in a great apron, and vigorously pasting on a new wallpaper. She received him with calm composure. There is a good portrait of her as an elderly lady in a cap, curving her hand round her ear to assist her hearing. She must have herself insisted upon being painted in this unusual attitude. She looks like a person of excellent understanding, whose mind has been much improved by reading.” Before he committed himself to matrimony Priestley took another step hardly less momentous. What it was may be gleaned from the following extract of a letter dated May 1, 1762, to Seddon, who was away at the time on one of his frequent begging expeditions on behalf of the Academy:—