On several occasions Room 40 received an unexpected but welcome gift when a German codebook was recovered after a sea battle and presented to the British code breakers. One such gift was a codebook from the German ship Magdeburg, a light cruiser that ran aground on an island off of Finland. When Russian ships quickly bore down on the cruiser, the captain of the stranded ship immediately did what all naval officers were taught to do: he ordered his signalman to bring him the ship's codebook so he could throw the book, wrapped in lead covers, into the sea. But before the signalman could deliver the book to his captain, he was killed by Russian guns. When the Russians recovered his body, the sailor was still clutching the codebook in his arms.

Which type of structure is used in the text?