invariably calculate the power of any sum; what does Pythagoras have to say to that."
"You never invented it," Temeraire said, irritable at having been woken up early, with so empty a day to be faced. "That is the binomial theorem, Yang Hui made it a very long time ago," and he put his head under his wing and tried to lose himself again in sleep.
He thought that would be all, but four days later, while he lay by his lake, the strange dragon landed beside him bristling and announced in a furious rush, her words nearly tumbling over one another in the attempt to get them out, "There, I have just worked out something quite new: the prime number coming in a particular position, for instance the tenth prime, is always very near the value of that position, multiplied by the exponent one must put on the number p to get that same value - the number p," she added, "being a very curious number, which I have also discovered, and named after myself - "
"Certainly not," Temeraire said, rousing with comfortable contempt, when he had made sense of what she was talking about. "That is e, and you are talking of the natural logarithm, and as for the rest, about prime numbers, it is all nonsense; only consider the prime fifteen - " and then he paused, working out the value in his head.
"You see," she said, triumphantly, and after working out another two dozen examples, Temeraire was forced to admit the irritating stranger might indeed be correct.
"And you needn't tell me that this Pythagoras invented it first," the other dragon added, chest puffed out hugely, "or Yang Hui, because I have inquired, and no-one has ever heard of either of them; they do not live in any of the coverts or breeding grounds, so you may keep your tricks. I thought as much; who ever heard of a dragon named anything like Yang Hui; nonsense."
Temeraire was neither despondent nor tired enough, in the moment, to forget how dreadfully bored he was, and so he was less inclined to take offense. "He is not a dragon, either of them," he said, "and they are both dead anyway, for years and years; Pythagoras was a Greek, and Yang Hui was from China."
"Then how do you know they invented it?" she demanded, suspiciously.
"Laurence read it me," Temeraire said. "Where did you learn any of it, if not out of books?"
"I worked it out myself," the dragon said. "There is nothing much else to do, here."
Her name was Perscitia. She was an experimental cross-breed of a Malachite Reaper and a light-weight Pascal's Blue, who had come out rather larger, slower, and more nervous than the breeders had hoped; and her coloring was not ideal for any sort of camouflage: the body and wings mostly bright blue and streaked with shades of pale green, with widely scattered spines along her back. She was not very old, either, unlike most of the once-harnessed dragons in the breeding grounds: she had given up her captain. "Well," Perscitia said, "I did not mind my captain, he showed me how to do equations, when I was small, but I do not see any use in going to war, and getting oneself shot at or clawed up, for no reason which anyone could explain to me. And, when I would not fight, he did not much want me anymore," a statement airily delivered, but Perscitia avoided Temeraire's eyes, making it.
"If you mean formation-fighting, I do not blame you; it is very tiresome," Temeraire said. "They do not approve of me in China," he added, to be sympathetic, "because I do fight: Celestials are not supposed to."
"China must be a very fine place," Perscitia said, wistfully, and Temeraire was by no means inclined to disagree; he thought sadly that if only Laurence had been willing, they might now be together in Peking, perhaps strolling in the gardens of the Summer Palace again; he had not had the chance to see it in autumn.
And then he paused, and abruptly raising his head he said, "You say you made inquiries: what do you mean by that? You cannot have gone out."
"Of course not," Perscitia said. "I gave Moncey half my dinner, and he went to Brecon for me and put the question out on the courier circuit; this morning he went again, and the word was in no-one had ever heard of anybody by those names."
"Oh - " Temeraire said, his