Note 191 — Chapter IV

“The Washington is stated to be of 2000 horses’ indicated power, and is 1750 tons Government measure, or 2000 tons carpenters’ measure; so her steam power is to her tonnage as one to one, while the Britannia has only one horse-power to 2¾ tons.[193] To go a little, however, more into detail: both vessels have two cylinders, I believe, of the same diameter, viz., 72 inches, and both have side beam engines; the stroke of the Washington is 10 feet; her boilers are able to carry (they say) 30 lbs. of steam; but, if we allow her only 23 lbs. ⨉ 13 vacuum, she will be still double the power of the Britannia with 5 lbs. ⨉ 13 lbs. i.e., = 900 horses’ power (450 ⨉ 2). I am now speaking of full steam, or at least both cutting off at the same point. The Herald (New York) says the Washington’s wheels are 39 feet in diameter, and 7½ feet dip; but the latter is of course an error, and probably means 7½ feet face; she has two boilers 36 feet ⨉ 15 on the plan; there are three furnaces, each 7 feet ⨉ 4 feet 6 inches ⨉ 6 = 189 feet. Well then, there you have data from which you may calculate how many horses’ power can be got off that great surface with anthracite and blowers. Her recipient heating surface must be large; she has flues, perhaps 12 inches in diameter.”