Tense
From Patrick O’Brian’s wonderful Master and Commander:
“Very well, Mr Dillon,” said Jack. “We will exercise the great guns.”
A four-pounder may not throw a very great weight of metal, and it may not be able to pierce two feet of oak half a mile away, as a thirty-two pounder can; but it does throw a solid three-inch cast-iron ball at a thousand feet a second, which is an ugly thing to receive; and the gun itself is a formidable machine. Its barrel is six feet long; it weighs twelve hundredweight; it stands on a ponderous oak carriage; and when it is fired it leaps back as though it were violently alive.
The Sophie possessed fourteen of these, seven a side and the two aftermost guns on the quarter deck were gleaming brass.
The tense shift here, from past to present and back to past, is very fine.