“Your loyalty to your master is commendable,” my father replied in a stiff tone, “but I would be remiss in my duty to let you be led astray. Had God meant us to fly like birds, he would have given Adam feathers, rather than creating him naked and in need of a fig leaf. Surely you must see this is folly.”

“Folly to those who are not bold enough to dream.”

With those words, Leonardo carefully lifted the miniature flying machine from the table. Holding it in both hands at arm’s length, he assumed his familiar tone of lecture that I knew well from the workshop.

“Consider this, Signor Angelo,” he went on. “Had you never before seen a bird in flight, you would call me mad or worse if I were to describe such a creature to you. For, without any knowledge that such a feat was possible, you would claim that no creature could leave the confines of the earth for the sky.”

He paused to raise and lower the model a few times, causing its cloth wings to flap in a quite birdlike fashion.

“And yet we all know that the falcon can soar with the clouds and that the lark flits from tree to tree with but the beat of a wing. Why should man, with his mighty intellect, not be able to devise a craft to mimic a bird’s form, thus allowing him to sever his bond with the earth and join his feathered brethren?”

With those words, he handed the model to my father, who took it with apparent reluctance. I saw a new spark of interest in his eyes, however, as he deigned to study the design.

“Hmmm… interesting,” he muttered, carefully turning the small machine about. Indicating the supporting portion of the wing framework, he added, “This piece appears overly heavy and rigid for its purpose. Replacing it with two narrow rods would lighten the weight and add flexibility while still maintaining stability. And certainly the choice of wood is a factor. You will require something with strength yet suppleness-perhaps ash-with special care taken for the quality of the grain.”

“And that is why I require your help, Signor Angelo,” the Master replied with a small smile. “While I am certain that my craft is soundly engineered, building it will require the expertise of a man who understands every nuance of the wood that will form it.”

My father merely snorted. Then, with a grudging nod, he conceded, “With the right materials, a large-scale version of this machine should prove but moderately difficult to build. Whether or not it can be made to fly is another issue. What manner of propulsion do you propose?”

“Ah, that is the easy part.”

Leonardo strode over to the shelves and held out a hand. My gaze followed, and I saw that he was reaching for a tiny hawk inexplicably perched there between two stacks of manuscripts.

After an instant of surprise-how had such a bird made its way into the Master’s workshop?-I realized that the feathered creature was long since dead. But so skillfully had the small raptor been mounted, with its wings spread wide and its head proudly tilted, that I almost expected it to take flight at his approach. Of course, it did not, and he carried it back to where my father and I stood.

“We know that a bird’s greatest strength lies in its breast,” he explained, holding the hawk in one hand and pointing to that portion of its anatomy with the other. “Those sturdy muscles allow its wings to beat with swiftness enough to send it aloft. In comparison, a bird’s legs are fragile limbs designed primarily for clutching at a branch for support or for hopping about short distances between flights.”

He set the stuffed bird upon the table and retrieved the model from my father. Returning the invention to its original spot on the table alongside its feathered counterpart, he detached the carved male figure fi xed atop it.

“Here is our source of power,” he declared, “but what remains is the question of how it should best be used.”

Deftly, he manipulated the figure’s jointed limbs. Now the wooden arms were extended to either side and the legs were bent, so that its stance mimicked the hawk’s flight-ready form.

“One might be inclined to try to duplicate the bird’s method of locomotion, with tucked legs and flapping arms,” he went on, “but such an experiment would prove faulty. No matter how strong the man, such a motion could be kept up for but a short time. For, unlike a bird, a typical human does not hold his greatest strength in his chest; rather his legs are the most powerful portion of his anatomy.”

He paused to reconfigure the wooden man so that its arms were bent and positioned close to its sides, while its nether limbs were extended to full length.

“To take advantage of that strength,” he explained, “I designed a pedal system that allows the greater might of the legs to exert the needed force to fl ap the wings.”

“So it will be almost like running in place,” I ventured as I tried to picture how this would work.

“Exactly,” he said with a nod. “The sky pilot-that is what I have dubbed the man who will operate those controls-will recline atop the flying machine and pedal vigorously to make the wings move up and down, giving the craft sufficient lift. Simultaneously, he will use his hands to control horizontal and vertical movement by manipulating cords that adjust the angle of both the wings and the rudder.”

His explanation complete, he returned the figure to its previous position atop the model.

“There are many other principles at work here, of course, but you now know the fundamental theory behind my design. Given that, Signor Angelo, do you still see only folly in this plan?”

My father frowned, holding the Master’s calm gaze with a troubled look of his own. I waited uneasily for his reply, knowing that my fate might well be affected by his decision. I could not deny that my first obedience must be to my father; still, Leonardo had become a parent of sorts to me, as well. Were I to be forced to choose between them, it would be a heart-wrenching decision, to be sure!

After a long moment, my father slowly shook his head. “I fear, Signor Leonardo, that I do not believe this machine of yours will ever fly,” he declared, the blunt words sending my heart plummeting toward my boots with the speed of an eagle diving for its prey.

But before I could give way to despair, his next words halted that figurative flight as he added, “Still, I have no doubt that you yourself are convinced that you can accomplish this fantastical feat. Under such circumstances, my own feelings matter naught. And so I will be honored to work alongside you on this project on behalf of the Duke of Milan.”

It was all I could do not to cheer this great news, but I contented myself with a broad grin. Leonardo looked pleased, as well, and grasped my father’s hands in his.

“We shall make fine partners… and Dino shall prove a worthy assistant, as well,” he added, including me in his smile. Reaching for the discarded length of oiled cloth, he quickly wrapped it about the model so that the small craft was well hidden and its lines blurred beneath the folds of fabric.

“But, for the moment, I think that Dino should rejoin his fellows,” he told my father. “For I wish now to show you my progress on the full-scale model, and I must make a rule that only you and I shall have access to the shed where it is kept.”

“Do not worry, Master. I understand,” I was quick to assure him. “I shall find Constantin, for he told me he will be spending the remainder of the afternoon taking measurements in the chapel for the new fresco. I am certain he can use another set of hands.”

“Very good. And fear not-you shall join your father and me in the morning to help finish testing our model.”

I left the pair and headed off to the small chapel in the duke’s private wing. Safely ensconced behind high walls and an iron gate, and with its own tower, that portion of the castle served as an ultimate stronghold against any outside army’s attempt at conquest. There, the duke could make a final stand should the fortress ever be overrun by one of his enemies. For now, however, the soldiers who guarded that entry gave me but a cursory look as I explained my errand and then let me pass.