The experiment is briefly recorded in the ‘Scots Magazine’ for November 1788, p. 566. At the conclusion of the trials the engine was placed in the library at Dalswinton House, and it is now in the South Kensington Museum. A drawing of the boat from a sketch by Alexander Nasmyth, who formed one of the party, is given in Woodcroft's book (p. 36). Miller made further experiments with a larger boat, for which Symington built another engine, in November and December 1789, in the Forth and Clyde canal.
On 14 April 1790 Miller's friend Robert Cullen (afterwards Lord Cullen), who was acquainted with James Watt, wrote in Miller's behalf to Watt expressing dissatisfaction on Miller's part with the performance of Symington's engines, on account of the great loss of power by friction, and declaring that from what Miller had seen of Boulton and Watt's engines he thought that they might be successfully adapted to the purpose of steam navigation. The letter, which was recently discovered at Soho after a search made at the request of the present writer, is printed in full in the ‘Engineer’ for November 1893. Watt's reply, dated 24 April 1790, is given by Williamson in his ‘Memorials of James Watt,’ 1856, p. 219. It was not encouraging; Watt seems to have considered Symington's engines ‘as attempts to evade our exclusive privilege.’ These letters furnish a sufficient explanation of the abandonment by Miller of experiments which at one time seemed to be full of promise.
Miller seems to have derived some assistance from the suggestions of James Taylor, who was then living in his family as tutor to his sons, and many years afterwards Taylor set up a claim to be regarded as part inventor. A similar claim was also advanced by Symington. The relative amount of credit to be assigned to Miller, Taylor, and Symington has been dealt with fairly and impartially by Woodcroft, by Major-general Miller, in ‘A Letter to Bennet Woodcroft vindicating the Right of Patrick Miller to be called the first Inventor of Practical Steam Navigation,’ London, 1862, and by Patrick Miller the younger (Edinb. Phil. Journ. 1825, xiii. 83, and art. Symington, William).
After abandoning the subject of steam navigation, Miller still paid attention to the improvement of naval architecture, and in May 1796 he obtained a patent (No. 2106) for ships with flat bottoms, of great capacity, and drawing very little water. In calms or light winds they were to be propelled by paddle-wheels, but the specification contains no mention of steam power.
With the poet Burns Miller maintained very agreeable relations. In December 1786 Burns writes: ‘An unknown hand left ten guineas for the Ayrshire bard with Mr. Sibbald, which I got. I have since discovered my generous unknown friend to be Patrick Miller, Esq., of Dalswinton.’ Several of Burns's letters to Miller, written after the poet became Miller's tenant, are printed in W. Chambers's ‘Burns.’
When nearly eighty years of age Miller introduced fiorin grass into Scotland, sending his steward, John Farish, to Ireland, where it had been cultivated with great success, to collect information. His report was published at Dumfries in 1810 under the title of ‘Treatise on Fiorin Grass.’ Miller's method of cultivating this grass is described at length in the Edinburgh ‘Farmers' Magazine,’ 1811, xii. 233; 1812, xiii. 3, 21, 203.
He died at Dalswinton House, 9 Dec. 1815, and was buried in Greyfriars churchyard, Edinburgh.
Miller married a Miss Lindsay, by whom he had five children: (1) Patrick, at whose instance Perry in 1794 offered to place Burns on the list of contributors to the ‘Morning Chronicle’ (Chambers, Burns, iv. 18); (2) William, captain in the horse guards, M.P. for Dumfriesshire, 1790, alluded to as ‘the sodger youth’ in Burns's election ballad, ‘The Five Carlines;’ (3) Janet, married to John Thomas, eighth earl of Mar and thirteenth lord Erskine (Marshall, Genealogist, 1878, ii. 80); (4) Jean, married to Leslie Grove Jones, lieutenant-colonel grenadier guards; and (5) Thomas Hamilton, advocate. After the father's death a dispute arose in the family respecting the disposition of his property, and the case reached the House of Lords, by whom it was remitted back to the Edinburgh court of session (see Journals of House of Lords, 1818 li. 542, 1822 lv. 465).
There is a portrait of Miller by Alexander Nasmyth, which was lent for exhibition in 1859–60 at the Patent Office Museum, by Miss Gregan of Dumfries; a copy is in the possession of the widow of Bennet Woodcroft. It was engraved in 1862 by Walker and Zobel as one of a group of inventors and men of science. Another, by an unknown artist, was presented to Woodcroft in 1861 by Mrs. Bairnsfather, a granddaughter of Miller, and is now temporarily deposited in the machinery and inventions department, South Kensington Museum. Mrs. Woodcroft also possesses a portrait-medallion by Wedgwood. A medallion by James Tassie is in the National Portrait Gallery, Edinburgh.
