With the financial assistance of several wealthy friends in New York, Ericsson proceeded to build a large sea-going vessel, to be propelled by means of hot air. It was a costly experiment, involving an outlay of $500,000, the engines alone costing $130,000. The cylinders were 168 inches in diameter, with six-feet stroke. The machinery was in motion within seven months of the laying of the vessel’s keel. On her trial trip the _Ericsson_ attained a speed of eight miles an hour, and subsequently as much as eleven miles an hour. The _Ericsson_ was at once a success and a failure. She sustained the inventor’s theory as to the power of heated air, _but_ so excessive was the temperature of the air required to develop the power, the cylinders were warped out of shape and some of the fittings were burned to a crisp. The costly experiment was consequently abandoned. The caloric engine was replaced by an ordinary steam-engine, and thus transformed the _Ericsson_ earned her living for many years. THE “MONITOR.” This further product of Ericsson’s fertile brain is in the form of an armour-protected, semi-submerged steam vessel for war purposes, and first came prominently into notice in connection with the memorable contest which took place in Hampton Roads on the 9th of March, 1862, between the _Merrimac_ and _Monitor_. The former was an old wooden vessel refitted by the Confederate Government at Norfolk navy-yard, and covered with protective armour to the water-line. The _Monitor_ was a flat iron boat resembling a scow, with nothing visible above water save the flush deck, from the centre of which rose a massive iron tower containing two guns of heavy calibre. The “cheese-box,” as the _Monitor_ was contemptuously styled, held her own against the _Merrimac_, which carried eleven guns. It was a drawn battle, but a victory for Ericsson, and resulted in many other steam vessels of this description being built for harbour and coast defence under his supervision. John Ericsson died in New York on the 8th of March, 1889. _Vide_ “Ericsson and His Inventions,” in _Atlantic Monthly_ for July, 1862, and “John Ericsson, the Engineer,” in _Scribner’s Magazine_ for March, 1890. II. THE WHALEBACK