"So what sort of weapon is it?" Potter asked curiously.
"Railguns."
"Railguns?" Harry asked in disbelief.
"Railguns!"
"Railguns?!" The dumbstruck Potter's eyes bulged until they were the size of plums.
"Yep!"
"Richie, are you taking the piss?"
"Nope."
"Come off it! That's impossible!"
"Harry, I'm serious. The wizards managed to fit a railgun into each arm of the glasses, based on the operating principle of a particle accelerator."
"Bloody hell!" Potter was utterly astonished. "So, are they powerful?"
"Ha! Powerful..." Richard drawled ironically. "They're fired by mental command. The railguns are controlled by the AI. For easier aiming, there's a virtual crosshair, like in computer games, projected onto the lenses. The projectile is a tiny metal particle weighing one-hundredth of a gram. The particle accelerator gets it up to seventy-seven kilometres per second. At that speed, the projectile burns up from friction with the air, producing a stream of superheated plasma that strikes the target. A shot like that can penetrate tank armour. Rate of fire is up to a thousand rounds per second. There's ten kilograms of ammunition stored in an expanded-space compartment inside the arms of the glasses. You can fire single shots, short bursts, or sustained bursts. And you've got two of these railguns!"
"Er..." Harry ran his right hand through his perpetually untidy hair. "Could you put that in normal words? Is seventy-seven kilometres per second a lot or not?"
Richard rolled his eyes theatrically, like an actor in a film.
"Harry, it's a bloody lot!" he said, finally descending to plain English. "The effect on the target depends on the power setting, which you can adjust. It ranges from three thousand joules—that's about the muzzle energy of an AK-47—all the way up to twenty-nine thousand six hundred joules, roughly the muzzle energy of a heavy machine gun. Effective range is up to a kilometre. You could send maniacs like Dobby to the next world by the thousand, shredding them into tiny pieces even if they were sitting inside tanks."
Harry went weak at the knees and sat down where he stood. His jaw dropped towards the floor, while his eyes seemed ready to pop out of their sockets. He imagined thousands of tanks crewed by house-elves advancing on Hogwarts. Then Harry strode out onto the Astronomy Tower, thrust out one hand towards the tanks and shouted, "You shall not pass! Not on my watch!" Then he activated his glasses and began pouring bursts of fire into the tanks, which fell apart before they could even reach the walls of Hogwarts.
Potter was dragged out of his fantasies by Grosvenor's actions. Richard took another pair of glasses from his bag—a stylish, narrow pair with yellowish lenses—and perched them on the bridge of his nose.
"Er..." Harry drawled. "Railguns?"
"No-o-o... Something wrong with my eyesight..."
There was so much sarcasm in Richard's voice that Potter did not doubt for a second that his friend had absolutely nothing wrong with his eyesight and that his glasses had exactly the same functions.
Potter took the control wristband from Richard and fastened it around his wrist. A menu immediately appeared before his eyes. He became so absorbed in exploring the artefact's functions that he failed to notice Hermione Granger entering the compartment.
"Hello, boys," she said. "I've been looking for you."
"Oh, Hermione!" Richard said happily, reaching into his bag. "I didn't manage to get your Christmas present ready in time. So, here..."
Harry's gaze locked onto a pair of glasses with pinkish lenses.
"Hey!" he exclaimed indignantly. "Richie, you're not seriously giving that to Hermione, are you?"
"Why not?" Grosvenor shrugged.
"Yes!" Hermione glared indignantly at Potter. "Why not?"
"But she's a girl!" Harry offered as his argument.
"Yes, she is," Richard agreed. "That's why hers have pink lenses."
"And what exactly is wrong with me being a girl?!" An extremely indignant Hermione planted her hands on her hips and loomed over Harry.
"Well..." Potter faltered. "It's a weapon... They're railguns..."
Hermione gave a contemptuous snort.
"Railguns!" she scoffed. "In a pair of glasses! Richie, just listen to what he's saying."
Hermione turned to Richard, expecting a comment and his support. But as she looked at his calm expression, doubt began to creep into her mind.
"That was nonsense, wasn't it?" she asked uncertainly.
Richard shook his head.
"Richie, you're joking, aren't you?" Hermione asked hopefully.
"Railguns," Richard confirmed with a nod. "Two of them… One in each arm. Up to a thousand rounds per second. Stopping power comparable to a heavy machine gun."
The girl's legs turned to jelly, and Hermione joined Harry Potter in sitting down. She sat there pale as chalk, staring at Richard with enormous eyes and blinking rapidly.
"Railguns? In glasses?! Richie, please, tell me you're joking!"
"Railguns, Hermione. I'm not joking. Give me your wristband and I'll update the software."
"Richie, have you gone mad?!" Granger exclaimed.
"Hermione, it was your idea," Grosvenor replied. "The glasses, at least. Harry came up with the railguns. Personally, I think the result is remarkably compact and lethal—just the thing for self-defence against deranged wizards."
"A heavy machine gun for self-defence?!" Granger whispered. "Oh yes, that's perfectly normal!" she added sarcastically.
"It's adjustable," Richard explained. "You can turn the power down to three thousand joules—then it's only about as powerful as an assault rifle. I suppose, Hermione, I'm going to have to repeat what I already told Harry..."