Whether he would have been called upon, had the Emperor’s gunboats been unsuccessful, is a point upon which there has been much conjecture. In designing these vessels, the Emperor had in mind that they should be cheaper and more easily and rapidly built than ships of the line, that they should draw little water, that they should be capable of being served by a small crew, and that they should be covered with an armour against which hollow shot fired from Paixhan guns “should be broken like glass,” according to the _Moniteur_. Experiments made at Vincennes revealed the required strength and thickness of the defensive iron plates. The external protection was to be able to defy alike shell, solid or hollow shot, cold or red-hot shot. The Imperial designer even chose the name of the type to indicate that these vessels were not to be considered as built to pursue an enemy, but were siege batteries, capable of attacking with energy and persistence fortifications heretofore regarded as unassailable by sea. The results of the preliminary artillery trials were communicated to the British, and trials made in England confirmed those of the French. The British authorities, being convinced that iron-clad vessels were necessary for the reduction of the Russian forts, followed the example of the French and ordered several. These vessels were required both in the Baltic and before Sebastopol. One of these floating batteries, intended for the attack on the Cronstadt forts, was the _Terror_. Beauty was one characteristic she did not possess. She was equally bluff at the bows and stern, and could move either end foremost to facilitate her manœuvring in an engagement. She was built, armour-plated, and launched in about three months; this rapidity of construction, as it was then considered, was due to Palmer’s invention, whereby plates were rolled instead of being forged. [Illustration: H.M.S. “WARRIOR.” _Photograph by permission of the Thames Ironworks, Shipbuilding and Engineering Co., Ltd._] [Illustration: THE “TERROR.” _By permission of Palmer’s Shipbuilding and Ironworks, Ltd._] The English-built _Glatton_ and _Trusty_ differed from the other floating batteries constructed at this time, as they were pierced for sixteen guns, as against twelve for the others. As innovations they were unmercifully criticised. Their portholes, measuring 3 feet 4 inches by 4 feet 10 inches, were considered much too large. They were rigged as three-masted schooners, of all rigs in the world, with two square sails on the foremast. “Why such things as these should be completely equipped and rigged, we cannot, for the life of us, divine. The Admiralty is decidedly masting mad.”[34]