The piece of timber which could slide back and forth in the slot under the mortar, and which had a saucer-like depression where the underside of the mortar barrel rested, was called the bed bolster. You levered up the muzzle with handspikes until it was at the right elevation, then you pulled on the two ropes and slid the bed bolster underneath until the barrel was supported. After that he was not sure what happened, so he had borrowed the gunner's notebook, although the handwriting was very difficult to read. He sat down on the mortar bed and concentrated.
He had not been reading for more than ten minutes when Thomas Jackson came along and inspected the gun.
"Looks as though it'd go right through the deck the first time you fired it," the American commented. "Still, there are three hundred shells for this one, and three hundred for the other -" he gestured aft to the other mortar. "The French presumably had faith in it."
Paolo looked at the sandy-haired, thin-faced American, and his jaw dropped with dismay. "Do you mean you wouldn't want to fire this if the captain gave you permission?"
"I'd sooner he gave me a direct order, sir," Jackson grinned, teasing the boy. "I've never had anything to do with these things. Always fired guns that shot horizontally. This is more like tossing a grenade over a wall and hoping to hit something you can't see."
"Exactly!" Paolo exclaimed. "You can't do that with an ordinary gun. If your enemy is behind the thick walls of a castle, or on the other side of the hill, you can't attack him with a cannon because it fires straight - more or less straight, anyway. With the mortar you can hurl shells down on him. Explosive shells."
"Yes," Jackson agreed as Stafford and Rossi walked up to listen to the conversation, "but the fuse that makes the shell explode inside the enemy's walls might also make it burst inside the mortar before you can fire it."
Paolo shrugged his shoulders with magnificent indifference. "You might slip and fall from a topsail yard, you might get a hernia, a roundshot might knock your head off the next time we go into action ..."
"Agreed, sir," Jackson said amiably, "but that's not to say I'm going to jump off a topsail yard deliberately, get a hernia, or stand and invite the enemy to knock my head off with a roundshot. When you play around with these mortars, though, you light the fuse in the shell, and if someone's made a mistake in the length or anything, it makes a big bang you never hear!"
"How heavy the shell?" Rossi inquired.
Paolo ran his finger down the page of the notebook, turned over the page and then said: "The gunner says this is about the same as the British 10-inch. And . . ." The tip of his tongue was protruding with the concentration. ". . . Ah, yes. 'Weight of shell when fired' - Mama Mia! It is ninety-three pounds - nearly a hundredweight! That's the hollow cast-iron ball and the powder inside."
"How much powder in it?"
"Only seven pounds."
"Seven?" exclaimed Rossi. "Why, that is nothing!"
Jackson said: "It doesn't need much to blast the shell casing into thousands of pieces. It's these splinters that do the damage."
" 'ow far will it toss a shell, then?" Stafford asked, peering down the bore like a farmer inspecting a horse's teeth.
"Wait," Paolo said, consulting the notebook. "It depends on the amount of powder in the charge. That's obvious, but as far as I can see, it's easier to use more or less powder than to change the elevation of the gun."
Stafford slapped the side of the mortar. "I should fink so; must weigh a ton!"
"One and a half," Paolo said, having just found some details in a neatly-written table. "Ah, here we are. First you must understand about the shell. It is round as you know, but it is cast so that it has the two carrying handles and the filling and fuse hole at the top." He read on a moment and said: "You might well ask why the shell falls the right way up - with the fuse at the top, because it might fall upside down and break off the fuse."
"We might well ask, sir," Rossi agreed politely. "Why does it fall with the fuse upside down?"
"No, no," Paolo said patiently. "Why it falls with the fuse uppermost."
"Yes," Rossi said, having lost track of the conversation, "that is most interesting, sir. But how lights the fuse, then?"
Paolo looked up in surprise and lost his place in the notebook as Stafford and Jackson started laughing. "Why the laughing?"
"We were waiting to hear why the shell falls the right way up after it's been fired, sir," Jackson said.
"Ah, yes. Well, although the shell casing looks like a circular ball from the outside, in fact the bottom is much thicker, and therefore heavier, so it drops first."
"Ah," Rossi said. "I was going to ask you about that, signor. But supposing you fire the shell and bang, it falls in the enemy fort with the fuse at the top and burning; what stops the enemy throwing a bucket of water at it and putting out the fuse?"
"Wait," Paolo said, "let me read more. There must be a reason why that will not work."
"I can fink o' one good reason," Stafford said emphatically. " 'oo'd be daft enough to walk up to a smoking shell with a bucket o' water? Not me! I'd duck down art of the way."
There were two or three minutes' silence while Paolo read through the pages, occasionally grunting to indicate an interesting point, but saying nothing, obviously absorbed by the mental picture of a shell lying in the castle courtyard with smoking fuse.
"Here we are," he exclaimed triumphantly. "The fuse burns at the rate of an inch in four seconds and forty-eight parts."
"Forty-eight parts of what?" Stafford asked.
Paolo looked appealingly at Jackson, who shrugged his shoulders. "Of a second, sir? Most likely a second is divided into a hundred parts. It's the sort of thing they do," he added darkly, knowing the unreliability of the Board of Ordnance.
"Well, it's not very long, is it... about half a second. Anyway, you know how long the shell takes to land, so you cut the fuse to the ..."
"How do you know how long it takes?" Rossi asked.
"Accidente! You have it here in the tables!" Paolo said crossly. "Now just listen. Just suppose your target is 680 yards away. You elevate the mortar to forty-five degrees. Then you put in a charge of one pound of powder; then you cut the fuse to burst ten seconds after you fire the mortar."
"Why ten seconds?" Rossi persisted.
"Mama mia, Rossi! Because it takes ten seconds for the shell to fly through the air and land on a target 680 yards away. That means it's no good having a bucket of water."
"Who cuts the fuse?" Jackson asked.
Paolo had just reached the page giving details of the fuse. "The fuse," he said, like a priest reading a liturgy, "is a conical tube made of beech, willow or some other dry wood. It is open at the top and at the pointed end. So it is filled with a mixture of sulphur, saltpetre and mealed powder - yes," he said quickly, anticipating Rossi's question, "obviously you keep a finger over the hole in the pointed end while you're doing it. Then each end - each hole, in other words - is covered with a composition of tallow and beeswax or pitch, to keep out the damp. When the fuse is put into the shell, the little end is cut off or opened, but the big end is left closed until just before firing.
"So, starting at the beginning, the shell itself is loaded with powder through the fuse hole in the casing. Then the fuse is inserted so that an inch and a half comes out beyond the fuse hole. Protrudes, it means," he explained, proud of his English. "You must make sure there is nothing to prevent the fire from the fuse exploding the powder in the shell - make sure the little end is clear, in other words.