In 1854, such marked progress had been made in the construction of ordnance that Mr. Stevens was no longer willing to proceed with the original plans, fearing that, were the ship completed, it might prove not invulnerable, and might throw some discredit upon its designer, as well as upon the navy of which it was to form a part. The work, which had, in those years of peace, progressed very slowly and intermittently, was therefore stopped entirely, the vessel given up, and in 1854 the keel of a ship of vastly greater size and power was laid down. The new design was 415 feet long, of 45 feet beam, and of something over 5,000 tons displacement. The thickness of armor proposed was 6-3/4 inches--2-1/4 inches thicker than that of the first French and British iron-clads--and the machinery was designed by Mr. Stevens to be of 8,624 indicated horse-power, driving twin-screws, and propelling the vessel 20 miles or more an hour. As with the preceding design, the progress of construction was intermittent and very slow. Government advanced funds, and then refused to continue the work; successive administrations alternately encouraged and discouraged the engineer; and he finally, cutting loose entirely from all official connections, went on with the work at his own expense. The remarkable genius of the elder Stevens was well reflected in the character of his son, and is in no way better exemplified than by the accuracy with which, in this great ship, those forms and proportions, both of hull and machinery, were adopted which are now, twenty-five years later, recognized as most correct under similar conditions. The lines of the vessel are beautifully fair and fine, and are what J. Scott Russell has called "wave-lines," or trochoidal lines, such as Rankine has shown to be the best possible for easy propulsion. The proportion of length to midship dimensions is such as to secure the speed proposed with a minimum resistance, and to accord closely with the proportions arrived at and adopted by common consent in present transoceanic navigation by the best--not to say radical--builders. The death of Robert L. Stevens occurred in April, 1856, when this larger vessel had advanced so far toward completion that the hull and machinery were practically finished, and it only remained to add the armor-plating, and to decide upon the form of fighting-house and upon the number and size of guns. The construction of the vessel, which had proceeded slowly and intermittently during the years of peace, as successive administrations had considered it necessary to continue the payment of appropriations, or had stopped temporarily in the absence of any apparent immediate necessity for continuance of the work, was again interrupted by his death.