Early evening, Friday; August, 06, 1830.
Chemistry laboratory at the Ecole Poytechnique.

Charles smiled in satisfaction, wiping some perspiration off his brow.
"'I think I have ground the gunpowder
mixture in the bell jar sufficiently fine, professeur." he said, looking to his mentor, Gay-Lussac who paid him scant attention at that moment while reviewing some notes that he had brought along with him.
"Good!" he growled softly, responding somewhat flippantly. The professor finally put the papers aside and glancing at his chain watch he mused with some concern,
"It looks like my distinguished friend and colleague, Professeur
Ampere is late. He is supposed to be bringing with him a reliable voltaic pile that he himself made for this experiment. We do need at least two for a good series connection. I do hope he has not been waylaid somewhere; it is getting dark out there now." he added, staring at the temporarily shuttered window nearby, and then over at the flickering oil lamp off to one corner of the room that was their sole source of light. He shrugged in disappointment,
"Oh well! We can perform this experiment tomo...what??"
Gay-Lussac turned, distracted by a distant faint metallic clatter of a key rattling in a lock, followed in short order by the muffled squealing of a door and then a reverberating clatter of footsteps that grew louder; becoming more obvious when it came from a nearby stairwell.
Giving his bright student-assistant a confident nod, "I'm sure that's him I hear coming." he affirmed, " I lent him a spare set of keys to this building yesterday."
Charles-Philippe, rubbing his fingers to restore circulation, eagerly rushed over to the laboratory entrance, hastily opening the door for the late arriving scientist-lecturer.
"Bonjour, Professeur Ampere. Welcome." Charles gushed.
"Bonjour, young man. I do remember seeing you at one of my lectures this past spring.
And I do recall the earlier incident with the horse and carriage." he smirked, "Charles-Philippe Valcour, is it?"
The science student nodded coyly.
I'm glad I could make it. I apologize to you both for my tardy arrival." their visitor explained, then turned to give his greetings to Gay-Lussac.
Gesturing to the invaluable package the distinguished visitor carried, Charles spoke, "I see you have brought along the additional voltaic pile that we need. I will be glad to take it. Do you want me to take your hat and coat as well, Professeur Ampere?"
"Merci. Indeed, do take the device off my hands! I will stow my own coat and hat." he replied, immediately handing Charles the portable electric-power
source.
Professor Ampere was soon scurrying about, examining the set-up for the experiment with great interest; his eyes going over every centimeter of the apparatus.
"I see that you have a glass bowl at the bottom of the bell jar with the ground up and mixed gunpowder ingredients spread in a thin layer inside." and added, "I also see that Monsieur Valcour your assistant here has drawn up the rod-and-disk pestle to a marked height. Hmmm, looks like the disk is - perhaps, ten centimeters above the bottom of the bowl - - - and the disk is made of iron, isn't it?"
Gay-Lussac nodded, explaining,
" We made sure the iron disk was free of rust to keep external sources of oxygen away from the powdered carbon and sulfur. Also it reduced the risk of there being an accidental discharge of static electricity. Now, as you can see..." he pointed out, indicating the continuing preparatory work that his young assistant was engaged in, "...how this young man is turning two handles on the top of this altered bell jar to swing two hooked copper wires close together over the glass bowl. Now watch!"
Both professors of science warily observed as Charles-Philippe pushed one hooked wire down into the gunpowder, pressing down on its connecting handle; then repeating this effort with the other: giving each of the handles one final adjustment to make sure the wire tips were only a few millimeters apart.
Charles stopped, looked up and nodded.
"We're ready to use the voltaic piles." he affirmed, "Professeur Ampere? For your safety please step behind this protective double-glass shield over here."
Momentarily mystified, Professor Ampere asked,
"Double-glass shield? How will that offer us protection should, heaven forbid, the bell-jar violently shatter?"
Gay-Lussac slapped his colleague's shoulder encouragingly, "Relax, my friend. There's a generous layer of clear gelatin between these two layers of glass. This simple but prudent form of protection is the idea and handiwork of Monsieur Valcour here. He's very intelligent and practical I confess."
"I agree." Andre Ampere nodded,
"I can see how it would work should things go perilously awry during this experiment. Glass shards flying off a shattered bell jar like grapeshot would likely shatter or fracture the
facing glass plate, but the soft gelatin would absorb the force of the impacts, keeping the glass plate on the opposite side undamaged. And the transparent gelatin would also allow us to observe the effects of the experiment with reasonable clarity.
I can see other practical applications for this - - - safety device.
Have you applied for a patent on it, young man?"
Charles paused coyly,
"Yes, I have, Professeur." he admitted, "Professeur Lussac has been kind enough to assist me in that effort."
"I'm not the least surprised." Professor Ampere smiled approvingly as he took his place behind the protective glass.
Gay-Lussac scooped up a pencil and notebook to record the science observations before joining the two men already prudently huddling in the cramped corner behind the glass shield.
They all looked anxiously at each other,
Andre Ampere uttering a small prayer before asking, "My dear friend, I do hope that the vacuum pump still attached to the jar
won't fly off and knock over the oil lamp over there should the experiment go disastrously."
Gay-Lussac soothingly shook his head,
"I wouldn't be concerned about it. We're only using four grams of powder." He then called out to Charles who was grimly holding two cloth-wrapped wires well apart,
"Monsieur Valcour! Now!"
A moment later there was an bright yellow-orange flash emitted from the bottom of the bell jar, followed by a sudden expansion
of hot gases and smoke; with whitish particulate matter from the smoke almost instantaneously depositing itself on the interior surface of the surprisingly unscathed bell jar glass. There was also the sound of a loud muffled "boom".
Furiously scribbling down his observations in his notebook, Professor Gay-Lussac paid scant attention to his two companions
who warily rose in silent relief and triumph,
glancing at each other for momentary assurance.
Concluding his writing for the time being he
abruptly arose, quietly and thoughtfully pondering the results as he did. Then in a moment of sudden spontaneity the three began to hug, kiss and slap each other on the back, joyfully
expressing their modest triumph. They had become the first experimenters to prove that gunpowder can be ignited, even detonated in a 'vacuum'.

An hour later:
Professor Gay-Lussac's office.

Charles-Philippe, as a youthful assistant to his renowned Polytechnique chemistry professor, tried to stay in the background, feeling somewhat inadequate in the presence of the two middle-aged scientists of repute who were at that moment enjoying their friendly chat accompanied by wine. All three had glasses in their hands containing some fine vintage graciously provided by Gay-Lussac.
The novel experiment that they had carried out an hour earlier with impressive results was still fresh on their minds and remained the main topic of conversation; Professor Lussac having finished writing up the relevant details in his science notebook and then had both Professor Ampere and Charles come over to his office nearby for a celebratory drink.
In his role as assistant to his chemistry professor, Charles had the task of taking a few necessary measurements. He used a thermometer to record the before and after temperatures on the exterior surface of the
bell jar. He measured the net barometric pressure of the gases created by the ignited gunpowder. He also measured how far the rod-and-disk pestle was shifted upwards by the detonation of the common explosive.
It was this last measurement result that would stick with Charles.
When the experiment was repeated the next day, instead of the air being almost completely pumped out it was kept at the same pressure as the air outside the bell jar was as an experimental "control". When that fresh gunpowder charge was detonated the rod-and-disk pestle was shifted upward no more than 80 percent of the distance the same pestle had been displaced by the 'explosion' of an equal amount of gunpowder in the air-evacuated bell jar.
Charles and his noted chemistry instructor and mentor would conclude and calculate that the gunpowder gases that evolved in the near-vacuum conditions had an expansion velocity that was somewhere
between 10 and 14 percent greater than similar gases expanding under normal atmospheric pressure. But that follow-up experiment, with its startling results, was yet to be
carried out; being an afternoon away...

The three experimenters continued to enjoy their wine and fellowship as that Friday night wore on; the two professors doing virtually all the talking.
Standing there listening, Charles-Philippe was intrigued by what he considered a profound statement uttered by Professor Gay-Lussac when he made mention of the late Monsieur Lavoisier's chemistry research and how it related to the experiment that they had performed that evening; describing the process of oxidization
that that 18th century scientist discovered as an affirmation of the "constancy of change" to be found in nature.
The two aging scientists continued talking for several more minutes, Charles remaining silent in the background for the most part.
However the phrase "constancy of change" lingered in his mind.
The young science student did
ponder something else that came to him; suddenly realizing a possibly that had not occurred to him previously.
Clearing his throat to get the attention of the two professors, he hesitantly asked them,
"Professeur Ampere? Professeur Lussac?
Do you think that a nitrous acid and powdered carbon mixture would be combustible in a vacuum as well?"
Their reply was swift, confident
and rather cavalier.
"Why not?" they replied in near unison, shrugging; immediately resuming the conversion the two had been carrying on between them as if Charles were not there. The conversation carried on for a few more minutes but then began to wilt: it was getting late and the wine glasses were almost empty.
As the wind-up clock in Professor Gay-Lussac's office chimed Ten O'Clock, his academic peer set aside his nearly drained glass, turning to take up his long coat and top hat, glancing over at his friend and fellow academic, smiling as he slipped them on.
"It has been a splendid and profitable evening, my good friend..."he remarked.
Then turning to look in the direction of Charles-Philippe, he asked, "Monsieur Valcour!"
Charles perked up.
"Yes, Professeur Ampere!"
"Having heard from my distinguished fellow scientist here that you have an interest
in the practical application of machines,
engines, prime movers, I have a book that may interest you. It is no longer in print, and it is exceedingly difficult to find a copy nowadays. It was written by the son of a famous engineer. perhaps you have heard of him. Nicholas Leonard Sadi Carnot."
Charles was flabbergasted. Feeling slightly numb he stammered out,
"Oh oh oh - yes! I have heard of him and I have been informed by others that his book contains unique insights into heat engines from a mathematical standpoint. You have a copy?" he inquired hesitantly.
"You can have it!" Professor Ampere declared, "I'll deliver it to Professeur Gay-Lussac. He will pass it on to you. Consider it a gift."
Charles was again momentarily speechless. At last he softly uttered, "Merci, Professeur Ampere."
"You're quite welcome, young man. But before I leave tonight, I have to ask you:
What practical application do you see emerging from this experiment that was carried out tonight?"
Charles thought for a second, then grinning mischievously, he replied, "Perhaps one day the army will mount a cannon on the Moon
and fire a projectile into orbit around that celestial body."

-------------------------------------

FOOTNOTE:

A little over ten months later, Charles-Philippe
Valcour, assisted by his friend and fellow science student, George-Richard Marchand
put together the same apparatus that had been used that Friday evening. And under the watchful eye of Professor Gay-Lussac, they
successfully ignited a small vacuum-frozen
mixture of powdered charcoal and a highly-concentrated quantity of what they called "nitrous acid" contained within that same bell jar.
The only real difference in the apparatus used in the experiments carried out ten months apart was the use of short lengths of borrowed gold wire, instead of copper, to set off an electric spark in the acidic mixture.
The slushy, highly corrosive and potent mixture, coated with a thin layer of acidic-ice not only ignited but generated an explosive flash and force that rivaled that of
an equal amount of gunpowder within the bell jar, resulting in it fracturing; something that had not happened with the gunpowder tests.
Charles did not need to take any measurements to affirm that the explosive
potency and energy of the "nitrous-acid" and powdered carbon solution was greater than that of exploding gunpowder, but he did cheerfully set about to formally gather the necessary measurements as he intended to do
after the successful climax of the experiment.
Neither he, nor Gay-Lussac, nor George-Richard realized at that time that they had taken an important step towards the development of a new form of rocket and rocket propulsion; those fiery projectiles
used at that time period being little more than
crude unreliable gunpowder-burning ordnance,
or fireworks.