The 4-inch Krupp steel armour on the _Monmouth's_ sides at the water-line, from the ram for three-quarters of the ship's length aft, cost to manufacture, in round figures, L60,000--equal to the total yearly income of four Archbishops of Canterbury or six Lord Chancellors. Two 'turtle-back' decks of thin steel armour further help to keep out shot. Altogether, in dead-weight, the armour all over the ship--on the sides, decks, bulkheads, conning-tower, casemates, barbettes, ammunition-supply tubes--amounts to 1800 tons, a fifth of the ship's entire displacement weight in sea-going trim. Then another detail, and the most important of all. Speed, for a cruiser, is, of course, the prime essential. It means the power of picking out a foe, of running down a foe, the command of the weather-gage, the choice of the range, the power of bringing on or refusing battle. Twenty-three knots an hour, or 26-1/2 statute miles, is the _Monmouth's_ best pace. Twenty-three knots an hour means the covering of a land mile in 2 minutes 36 seconds; or 100 yards in 7-4/5 seconds. In modern athletics 9-3/5 seconds is the record for 100 yards. The record for the Oxford and Cambridge boat race works out at under 11 knots an hour--considerably less than the _Monmouth's_ everyday cruising speed in time of peace. How it is done is, of course, an engine-room affair. Two main engines drive the ship: one engine to each of the immense 16-feet-wide twin-screws. At full speed they work up to an aggregate power of twenty-two thousand horses: eleven thousand horses each engine. Thirty-one boilers, of the much-maligned Belleville type, supply the steam. What that means the staff below have good reason to know. The thirty-one boilers, with their 'economisers,' provide seven thousand tubes to be looked after and kept clean. Collectively, the boiler-tubes offer to the fires in the stoke-hold a total heating-surface of 50,300 square feet: an area, that is, of an acre and a sixth, a space about equal to Trafalgar Square within the roadway, or the floor-space of the Albert Hall. Each boiler has two furnaces to heat it, making sixty-two in all. When all are alight they burn 40 tons of coal at once, on a grate-area of 1610 square feet; practically giving off a square space of flame 170 yards each way. The main engines, however, are by no means all. There are on board sixty-five separate 'auxiliary engines' besides. The weight of the machinery alone on board the _Monmouth_, amounts to 1750 tons--a fourth of the total weight of the ship.