The military mast was introduced in the sea-going turret ships like the _Devastation_, and a few years later all such masts were given fighting-tops or platforms upon which machine guns or small quick-firing guns were mounted, or were equipped with search-lights. These masts were of steel and hollow, and in some ships the tops could be reached by ratlines and shrouds in the old-fashioned way, and in others by means of internal or external ladders affixed to the masts themselves. Conning-towers were introduced later, but to meet the wishes of naval officers alternative places of control are also provided in all large ships, for use in case the conning-tower should be made the target for the concentration of the fire of a hostile ship. The experiments with the _Glatton’s_ turret proved the unsuitability of turret armour being made with horizontal joints, as there is always the chance that a projectile may strike the actual line of joining, where the resistance would be less than at any other part. The plates for the _Devastation_ turrets were, therefore, rolled sufficiently broad to cover the faces of the turrets from the breastwork deck to the upper edge, and only vertical joints were exposed to fire. The forward end of the ship was raised to form what was called a sunk forecastle. This considerably added to the freeboard forward and to the buoyancy at that end of the ship, and this was further augmented by the armour belt being reduced as much as possible so as to avoid unnecessary weight. Some critics of this design maintained that the end was too weak, and that the advantage it was sought to gain in sea-going qualities would not materialise; but when the vessel afterwards went to sea and was tested in all sorts of weather, and against heavy seas, in broadside seas, and in following seas, and in seas running a few points off the bow, or on the quarter, she proved herself an admirable sea-boat. An account of the sea trials in which she was accompanied by the _Agincourt_ and _Sultan_ includes a description written by a “scientific observer,” who was on board the _Devastation_. Her sea trials took place during the summer of 1873. The _Sultan_ was one of the more modern ironclads carrying a two-deck battery on a protected water-line, and the _Agincourt_ was a five-masted ship reminiscent of the steam frigate days. The scientific observer states:--