The Stevens brothers exerted their influence also on naval construction. A double invention of Robert and Edwin, the forced draft, to augment steam power and save coal, and the air-tight fireroom, which they applied to their own vessels, was afterwards adopted by all navies. Robert designed and projected an ironclad battleship, the first one in the world. This vessel, called the Stevens Battery, was begun by authority of the Government in 1842; but, owing to changes in the design and inadequate appropriations by Congress, it was never launched. It lay for many years in the basin at Hoboken an unfinished hulk. Robert died in 1856. On the outbreak of the Civil War, Edwin tried to revive the interest of the Government, but by that time the design of the Stevens Battery was obsolete, and Edwin Stevens was an old man. So the honors for the construction of the first ironclad man-of-war to fight and win a battle went to John Ericsson, that other great inventor, who built the famous Monitor for the Union Government. Carlyle's oft-quoted term, "Captains of Industry," may fittingly be applied to the Stevens family. Strong, masterful, and farseeing, they used ideas, their own and those of others, in a large way, and were able to succeed where more timorous inventors failed. Without the stimulus of poverty they achieved success, making in their shops that combination of men and material which not only added to their own fortunes but also served the world. We left Eli Whitney defeated in his efforts to divert to himself some adequate share of the untold riches arising from his great invention of the cotton gin. Whitney, however, had other sources of profit in his own character and mechanical ability. As early as 1798 he had turned his talents to the manufacture of firearms. He had established his shops at Whitneyville, near New Haven; and it was there that he worked out another achievement quite as important economically as the cotton gin, even though the immediate consequences were less spectacular: namely, the principle of standardization or interchangeability in manufacture. This principle is the very foundation today of all American large-scale production. The manufacturer produces separately thousands of copies of every part of a complicated machine, confident that an equal number of the complete machine will be assembled and set in motion. The owner of a motor car, a reaper, a tractor, or a sewing machine, orders, perhaps by telegraph or telephone, a broken or lost part, taking it for granted that the new part can be fitted easily and precisely into the place of the old.