“This is very instructive,” murmured Aunt Diana, moving nearer to her niece. “Miss Sharp, pray call your pupil’s attention to this remarkable relic.” For Mokes had seated himself sulkily on one of the veteran cannon which frowned over the harbor like toothless old watch-dogs. There was no objection to an army Antinous as a picturesque adjunct, Aunt Diana thought; but it was well known that there was very little gold in the service outside of the buttons, while here at hand was a Crœsus, a genuine live Crœsus, sitting sulky and neglected on his cannon! “Oh, certainly,” said Miss Sharp, coming to the rescue. “Iris, my child, you observe that it is in the form of a trapezoid--” “Trapezium,” said the Professor--“trapezium, Miss Sharp, if you please.” “‘That daring young man on a--’” chanted the Captain under his breath, as if in confidence to the southeast tower. “In the salient angles of the bastions are four turrets or bartizans,” continued the Professor. “Oh yes; how interesting!” ejaculated the governess, clasping her lisle-threads together. “Partisans!” “Bar-ti-zans,” repeated the Professor, with cutting distinctness. “The moat, as you will notice, is fortified by an internal barrier, and there is an outer wall also which extends around the whole, following its various flexuses. By close observation we shall probably be able to trace the lines of the abatis, scarp, counterscarp, and fraise, all belonging to the period of mediæval fortification.” “The Great Work is evidently to the fore now,” whispered Sara, as we sat together on a second cannon. “The lunette, now, is considered quite a curiosity,” said the Captain, briskly breaking in. “Miss Carew, allow me to show it to you.” “Lunette!” said the Professor, with lofty scorn. “That is what we call it down here, Sir,” replied Antinous, carelessly. “Miss Iris, there, is an odd little stairway there--” “Lunette!” repeated the Professor again. “But that is an example of the lamentable ignorance of the age. Why, that is a barbacan, the only remaining specimen in the country, and, indeed, hard to be excelled in Europe itself.” “I have heard it described as a demi-lune,” I remarked, bringing forward my one item, the item I had been preserving for days. (I try to have ready a few little pellets of information; I find it is expected, now that I am forty years old.) The Professor took off his tall silk hat and wiped his forehead despairingly. “Demi-lune!” he repeated--“demi-lune! The man who said that must be a--” “Demi-lunatic,” suggested John. “Forgive me, Miss Martha; it isn’t mine, it’s quoted.” We crossed a little draw-bridge, and passed through the ruined outwork, barbacan, lune, or demi-lune, whichever it was. Iris and the Captain had disappeared. At the second draw-bridge we came face to face with the main entrance, surmounted by a tablet bearing an inscription and the Spanish coat of arms.