of corresponding power, and was placed more than four feet below the
water-line. The boilers were also below the water-line, having a
peculiar heating-apparatus attached which effected a great saving of
fuel, and with their furnaces and flues so constructed as to burn
anthracite as well as bituminous coal. Instead of the ordinary tall
smoke-pipe,--an insuperable objection to a steamer as a ship of
war,--he constructed a smoke-pipe upon the principle of the telescope,
which could be elevated or depressed at pleasure; and in order to
provide a draught independent of the height of the smoke-pipe, he
placed centrifugal blowers in the bottom of the vessel, which were
worked by separate small engines,--an arrangement originally applied
by him to marine engines in the steam-packet Corsair in 1831. Thus the
steam-machinery of the Princeton fulfilled the most important
requisites for a war-steamer, combining lightness, compactness,
simplicity, and efficiency, and being placed wholly out of reach of the
enemy's fire.

The armament of the ship also exhibited many peculiarities. "By the
application of the various arts to the purposes of war on board of the
Princeton," says Captain Stockton, in his report to the Navy
Department, "it is believed that the art of gunnery for sea-service
has, for the first time, been reduced to something like mathematical
certainty. The distance to which the guns can throw their shot at every
necessary angle of elevation has been ascertained by a series of
careful experiments. The distance from the ship to any object is
readily ascertained with an instrument on board, contrived for that
purpose, by an observation which it requires but an instant to make,
and by inspection without calculation. By self-acting locks, the guns
can be fired accurately at the necessary elevation,--no matter what
the motion of the ship may be." The instruments here referred to,