Severian’s sword Terminus Est is a long, heavy executioner’s sword with a channel in the spine through which a river of mercury flows. The mercury changes the balance of the sword as it descends and makes the blade feel alive.<br><br> I had always thought the mercury channel was an interesting but improbable feature. The channel would weaken the sword and the empty area of the channel would have to be a vacuum, because air in the channel would impede the flow of the mercury. If the steel around the vacuum channel were not thick enough, atmospheric pressure would crush the blade.<br><br> Some people have argued that the advanced technology that produced ray guns and time travel would have no problem producing such a sword without the blade being weak. But I think appealing to advanced technology takes the fun out of speculating. <br><br> Wolfe has an engineering background
and most technological marvels in his books have some basis in fact. I began wondering if you could produce Terminus Est without resorting to the deus ex mechina of advanced technology.<br><br> The world of Urth has a lot of left-over marvels from the science of the past, but most of the inhabitants live a life with the technology of the middle ages. Sword-making is an ancient art and medieval craftsmen created fine blades. Terminus Est could be made as follows:<br><br>1. Forge the sword as a swordsmith normally would, heating and hammering and folding the steel.<br>2. After the sword is finished, drill a hole from the tang in the rear to close to the tip of the blade.<br>3. Holding the blade tip-down, fill half the channel with mercury.<br>4. Use a vacuum pump to expel the air, and then weld a plug at the base of the tang. (Okay, vacuum pumps
aren’t medieval, but they were in use by the latter half of the 1600’s.) Or you might create a vacuum by filling the whole channel with mercury with a curved glass tube at the end. Flip the sword over and the mercury would run down the channel and up the tube until atmospheric pressure balanced the weight of the mercury.<br><br> If Terminus Est is 1 inch in thickness at the spine and if the channel is ¼ inch in diameter, the walls would be 3/8 inch thick. This is enough to prevent the atmosphere from crushing the blade.<br><br> The blade of Terminus Est is an ell long (40 inches) and the grip is two spans (16 inches) (Shadow, XIV). So the sword is about 56 inches in total. Leaving an inch at the tip and the tang, you could make a channel 54 inches long. If half the ¼ inch diameter channel if filled with mercury, the weight of the mercury would be about 10
ounces. This would be enough to affect the balance and make the sword feel alive as you raised the blade and struck.<br> By increasing the diameter of the channel, you could increase the weight of mercury. But a larger channel further weakens the sword. I think a ¼ inch diameter channel leaves the sword with sufficient strength and provides enough mercury to make the sword behave as Severian describes.<br><br> The channel would still weaken the blade but not enough for it to break under normal use. Terminus Est shatters only when Baldanders hits it with his mace (Sword, XXXVII).<br><br> So I’ve changed my mind about the improbability of Wolfe’s putting a mercury channel in Terminus Est. I think a craftsman could have forged the sword without resorting to unknown technologies.<br><br><br>Jack<br><br><BR><BR>Best wishes,<br><br>Jack