The first iron steamer built by the Cunard Company was the _Persia_, and she deserves more than a passing mention because of the association with her of David Kirkaldy, Napier’s draughtsman, to whom modern steel shipbuilding owes the discovery of the way to toughen steel and remove its brittleness. Kirkaldy’s drawings of the _Persia_ are stated to have been the only steam-ship designs ever exhibited at the Royal Academy. He was also the first on the Clyde to give the question of trial performances the attention it deserved. The first trial trips recorded by him, on the _Larriston_, on September 22 and October 18, 1852, were printed when the Admiralty asked for particulars of the respective behaviour of a Smith’s and a Griffith’s propeller. But he was not allowed to continue his researches in this direction, and even the _Persia_ left the Clyde without a single diagram having been taken, for although Kirkaldy was in the engine-room during the entire trial, he had not permission to record her performances. He obtained data concerning many vessels “so as to be able to deduce the variations of behaviour and relative economy, and trace such to their respective origins, _e.g._, whether any variation was due wholly or in part to the difference in the shape of the vessels, in the propellers, in the engines, or in the boilers. The utility of these investigations was signally demonstrated in the case of two vessels, _Lady Eglinton_ and _Malvina_ ... the former proved a great success on her trial trip, and the latter a comparative failure. He was able to trace the cause of the failure and in great measure to rectify it. He clearly foresaw that the time was surely approaching when his employers would require to estimate for and construct vessels to fixed requirements as to draught, speed, and economy of working.”[87] [87] “Illustrations of David Kirkaldy’s System of Mechanical Testing,” by Wm. G. Kirkaldy. The drawings of the _Persia_ were made for his own pleasure, and the first intimation of their existence was the announcement in the papers that they had been admitted to the Academy. By Napier’s instructions they were exhibited at the Paris Exhibition of 1855 together with drawings of the steam-ships _Europa_, _America_, _Niagara_, and _Canada_. Napier received a gold medal and the Legion of Honour as exhibitor, and Kirkaldy received a medal as draughtsman. The drawings of these four ships were placed in the Louvre Museum after being presented to the Emperor Napoleon.