The story of the destruction of _Koenigsberg_ by the twin monitors _Severn_ and _Mersey_ in the Rufigi Delta, has an interest that far transcends the intrinsic military importance of depriving the enemy of a cruiser already useless in sea war. For the narrative of events will bring to our attention at once the extreme complexity and the diversity of the tasks that the Royal Navy in war is called upon to discharge. It is worth examining in detail, if only to illustrate the novelty of the operations which officers, with no such previous experience, may at any moment be called upon to undertake, and the extraordinary combination of patience, courage, skill, and energy with which when experience at last comes, it is turned to immediate profit. The incident possesses, besides, certain technical aspects of the very highest importance. For it gives in its simplest form perfect examples of how guns should not and should be used when engaged in indirect fire, and by affording this illuminating contrast, is highly suggestive of the progress that may be made in naval gunnery when scientific method is universally applied. The incident, then, is worth setting out and examining in some detail, and there is additional reason for doing this, in that the accounts that originally appeared were either altogether inaccurate or so incomplete as to be misleading. First, then, to a narrative of the event itself. _Koenigsberg_ was a light unarmoured cruiser of about 3,400 tons displacement, and was laid down in December 1905. She carried an armament of ten 4.1-inch guns, and was protected by a 2-inch armoured deck. The Germans had begun the construction of vessels of this class about seven years before with _Gazelle_, which was followed in the next year by _Niobe_ and _Nymphe_, and then by four more--including _Ariadne_, destroyed by _Lion_ in the affair of the Heligoland Bight--which were laid down in 1900. Two years later came the three _Frauenlobs_, and the _Bremen_ class--five in number--succeeded these in 1903-4. In 1905 followed _Leipzig_, _Danzig_, and finally the ship that concerns us to-day. All these vessels had the same armament, but in the six years the displacement had gone up 1,000 tons. The speed had increased from 21½ knots to about 24, and the nominal radius of action by about 50 per cent. _Koenigsberg_ was succeeded by the _Stettins_ in 1906-7, the two _Dresdens_ in 1907-8, the four _Kolbergs_ in 1908-9, and the four _Breslaus_ in 1911. _Karlsruhe_, _Grodenz_, and _Rostock_ were the only three of the 1912-13 programmes which were completed when the war began. The process of growth, illustrated in the advance of _Koenigsberg_ over _Niobe_, was maintained, so that in the _Karlsruhe_ class in the programme of 1912, while the unit of armament is preserved, we find that the number of guns had grown from ten to twelve; the speed had advanced from 23½ to 28 knots, and the displacement from 3,400 to nearly 5,000 tons. As we know now, in the