“You found some way to procure maiden boys in quantity?”

He snorted, very Mordecai-like. “Sometimes there are benefits in coming from a humble family. When I first tasted the element, as you just did, I recognized it as another and much less exquisite substance. My father was a fish peddler, and to make the fillets of cheap fish look more delectably pink, he soaked them in a brine of the lowly salt called saltpeter. That is all the autumn stone is—saltpeter. I do not know why it should be present in boys’ urine, and I do not care, for I have no need of boys to make it. Kithai is abundantly supplied with salt lakes, and they are abundantly rimmed with crusts containing saltpeter. So, these many centuries after the flaming powder was first compounded by some Han genius of al-kimia, I, merely the inquisitive son of the Jewish fish peddler Shi, am the first to make it in vast quantities, and to make the glorious displays of its fiery trees and sparkling flowers enjoyable by all men everywhere.”

“Master Shi,” I said diffidently. “In addition to my admiration of the beauty of those works, I have been struck by the thought of turning them to more useful account. The thought came to me when my own horse shied and bucked at first seeing a display of the fiery trees. Could not these engines of yours be used as weapons of war? To break up a cavalry charge, for example?”

He snorted yet again. “A good idea, yes, but you are more than sixty years late with it. In the year when I was born—let me see, that would have been by your Christian count the year one thousand two hundred fourteen—my native city of Kai-feng was first besieged by the Mongols of the Khan Chinghiz. His horse troops were affrighted and dispersed by balls of fire which flew into their midst, trailing sparks and whistling and banging. The Mongols were not stopped for long, needless to say, and they eventually took the city, but that valiant defense contrived by the Kai-feng Firemaster became legendary. And, as I told you, we Jews are great rememberers of legends. Thus it was that I grew up enthralled by the subject, and finally myself became a Firemaster. That employment of the flaming powder at Kai-feng was its first recorded use in warfare.”

“Its first,” I echoed. “Then it has been used since?”

“Our Khan Kubilai is not a warrior likely to ignore any promising tool of war,” said Master Shi. “Even if I were not personally interested in trying new applications of my art, and I am, he has charged me with investigating every possible use of the huo-yao for war missiles. And I have had some partial successes.”

I said, “I should be gratified to hear of them.”

The Firemaster seemed hesitant to confide. He looked from under his fungoid eyebrows at me and said, “The Han have a story. Of the master archer Yi, all his life prevailing over every foe, until he taught all his skills to an eager pupil, and that man finally slew him.”

“I do not seek to appropriate any of your ideas,” I said. “And I will freely tell you any that might occur to me. They could be of some small worth.”

“The danger of beauty,” he mumbled. “Well, are you acquainted with the large, hairy nut called the India nut?”

Wondering what that had to do with anything, I said, “I have eaten its meat in certain confections served at table here.”

“I have taken hollowed-out India nuts and packed them full of the huo-yao, and inserted wicks to supply the spark after a suitable interval. I have done the same with joints of the stout zhu-gan cane. Those objects can be thrown by a man or a simple catapult into an enemy’s defenses and—when they work properly—they let loose their energy with such explosive force that a single nut or cane would well nigh wreck this whole house.”

“Marvelous,” I said.

“When they work. I have also used cylinders of larger zhu-gan cane in another manner. By inserting one of my flying engines into a long empty cane before lighting its wick, a warrior can literally aim the missile like an arrow, and send it flying toward a target, more or less straightly.”

“Ingenious,” I said.

“When it works. I have also made missiles in which the huo-yao is compounded with naft oil, with kara dust, even with barnyard dung. When they are hurled into an enemy’s defenses, they spread an almost inextinguishable fire, or a dense, stinking, choking smoke.”

“Fantastic,” I said.

“When they work. Unfortunately, there is one flaw in the huo-yao that renders it totally impractical for military use. Its three component elements, as you have seen, are finely ground powders. But each of those powders has a different inherent density, or weight. Therefore, no matter how tightly the huo-yao is packed into a container, the three elements gradually separate out from one another. The least movement or vibration of the container makes the heavier saltpeter discombine and sift down to the bottom, so the huo-yao becomes inert and impotent. Thus it is impossible to make and store any supply of any of my inventions. The mere movement of them into a storehouse, not to mention out of it, causes them to become absolutely useless.”

“I see,” I said, sharing his air of deep disappointment. “That is why you are perpetually on the road, Master Shi?”

“Yes. To arrange a fiery-tree display in any city, I must go there and make the things on the spot. I travel with a supply of paper tubes, wicks, barrels of each of the constituent powders, and it is no great chore to mix the huo-yao and charge my various engines. That is obviously what the Kai-feng Firemaster did, when my city was besieged. But can you imagine doing all that in wartime, in the field, in the midst of battle? Every company of warriors would have to have its own separate Firemaster, and he to have at hand all his supplies and equipment, and he would have to be inhumanly quick and proficient. No, Marco Polo, I fear that the huo-yao will forever be only a pretty toy. There seems no hope of its military application, except in the occasional case of a city under siege.”

“A pity,” I murmured. “But the only problem is the powder’s tendency to separate?”

“That is the only problem,” he said, with heavy irony, “just as the only impediment to a man’s flying is that he has no wings.”

“Only the separation … ,” I said to myself, several times, then I snapped my fingers and exclaimed, “I have it!”

“Have you now?”

“Dust blows about, but mud does not, and hardened clods do not. Suppose you wetted the huo-yao into mud? Or baked it into a solid?”

“Imbecile,” he said, but with some amusement. “Wet the powder and it does not burn at all. Put a baking fire to it and it may blow up in your face.”

“Oh,” I said, deflated.

“I told you, there is danger in this stuff of beauty.”

“I am not over timid of danger, Master Shi,” I said, still pondering the problem. “I know you are busy preparing for the New Year celebrations, so I would not obtrude my company upon you. But, while you are occupied, would you let me have some jars of the huo-yao, so that I could speculate on ways and means—”

“Bevakashà! This is nothing to play with!”

“I will be most careful, Master Shi. I will not ignite so much as a pinch of it. I will but study its properties and try to think of a solution to the problem of its sifting down—”

“Khakma! As if I and every other Firemaster have not devoted our lives to that, ever since the flaming powder was first compounded! And you, who never even saw the stuff before—you truly are suggesting that I play the master archer Yi!”

I said, with insinuation, “So might have spoken, once upon a time, the Firemaster of Kai-feng.” There was a short silence, and I said, “The inquisitive son of a Jewish fish peddler might not have been trusted, either, to bring a new idea to the art.”

There was another and longer silence. Then Master Shi sighed and said, evidently to his deity: