is meant[1] The 'indicated' power developed, that is, the real effective power, varied from about two and a half times the nominal in the case of the 'Gorgon,' in 1837, till it reached more than seven times the nominal in the 'Inconstant,' in 1869. The absurdity and inconvenience of expressing the power of ships’ engines by a system of notation absolutely without meaning became so evident that in 1872 the indicated power was ordered to be given in the official Navy List.
Exactly contemporaneous with the 'Terrible' was the 'Inflexible,' the first steamship in the navy to make a voyage round the world. No better example can be given of the difference between steam navigation in the Royal Navy at that date and the present than the performance of the 'Inflexible,' which was then considered highly creditable, as indeed it was, to Captain John C. Hoseason, who commanded her and furnished an interesting account of it. She was what in those days was called a sloop, of 1122 tons burthen — not to be confounded with displacement[2] —
- ↑ 'Nominal' horse power was a standard adopted by James Watt for commercial purposes, in which the effective pressure and speed of piston were assumed to be constant quantities in all engines. The rule was well enough when first devised, but the extraordinary thing is that it should have remained in force so long under such entirely different conditions.
- ↑ 'Tons burthen,' or old measurement as it is often called, was, like 'nominal' horse power, a purely commercial expression. It was obtained by multiplying the 'length for tonnage' — which was found by deducting three-fifths the breadth of the ship from the length, taken at the water line — by the whole breadth and by the half breadth and dividing the product by ninety-four. Displacement tonnage, now in universal use, means the number of tons weight of sea water displaced by a ship floating at her load draught.
