The _boilers_ of the _Arctic_ were peculiar to the Collins line, and their merit was principally due to Mr. Faron, who acted as chief engineer of the company. They were arranged with double furnaces, and lower water-spaces connected by a row of vertical tubes, around which the heated gases circulated, with a hanging bridge or plate, which checked their otherwise rapid flow to the chimney and rendered the combustion more perfect. The heating surface was principally confined to the tubes and consequently vertical, the height of the smoke-pipe above the grates, 75 feet, insured a strong natural draft, and the proportion of heating to grate surface, was unusually large, being 33¼ to 1. The ratio of evaporation of sea water, during the quick trip of the _Baltic_ in February 1852, was 8·55 pounds of water per pound of anthracite.[198] Mr. Collins, under the advice of his engineer, originally intended to use fresh water entirely in these boilers, previously condensed from sea water, and an arrangement was made with J. P. Pierson, the inventor of the “double vacuum condenser,” to furnish condensers. But the tubes, which had been manufactured in England, were lost at sea, and the vessels were equipped without them. Bituminous coals alone were used until the superior qualities of anthracite were in several particulars shown to be of great importance in ocean steamers, when it was determined to use the former only _on the return trips_; and such became the established practice, resulting from an extended and careful series of experiments.[199] The _Pacific_ was a three-decked ship, very high on the water, and consequently much more comfortable for passengers than the other vessels; while the straight line of her bows, and freedom from encumbrances on her upper deck, offered less resistance to the wind. Her model under the water-line resembled somewhat the river boats; she had a flat bottom, her immersed section being not far from a parallelogram. Her bows and stern were formed by nearly plain surfaces, which, joined together, constituted an angle much more acute than was considered safe for adoption in ocean navigation some years ago. [Sidenote: Engines.]