After dinner, Jin and the others were discussing the results of the investigation.

The reason for this was that Marcia and Rodrigo had returned in the evening.

"A submarine is a ship, isn't it?

Marcia said.

"......, so one is for monitoring the crust, one is for storing materials, and the other is an unmanned submarine."

"Hmm. ...... but that propulsion system sounds interesting. Couldn't we apply it to a normal ship?"

"Haha, sounds like Marcia. ......Wait!　......Yes!

?"

Jin seemed to have come up with something and went to the workshop, returning immediately. In his hand was a piece of cardboard, a pair of scissors, and a candle.

As a side note, the word "cardboard ball" means "board" in English. It means .

<

The original raw material was straw pulp, and this is the yellowish paperboard.

White cardboard is made from wood pulp.

Jin was holding such cardboard in his hand.

By the way, it is really an ordinary cardboard. It was not made in Horaijima.

"What are you doing with it?"

Marcia asked, and Jin answered with a smile.

"You'll have to wait until it's finished.

Then Jin cut a piece of cardboard with scissors and made a small boat about 10 mm wide and 20 mm long.

Jin painted wax on it.

Marcia and the others in the cafeteria could guess that he was applying the wax to prevent water from seeping into the paper, but they could not tell what the final purpose was.

"There we go."

Jin then asked Perido 1, the five-colored golem maid, to bring camphor for the wardrobe.

Camphor is a wax-like crystal obtained from camphor trees and has a distinctive odor.

It has long been used to repel insects, but has been replaced by synthetic insect repellents such as naphthalene and paradichlorobenzene.

Here in Horai Island, camphor is extracted from natural camphor trees by extraction and purified by purification.

The camphor tree was used as wood after the camphor was extracted.

Jin made a notch in the stern of the ship and placed the camphorwood there.

"There we go. ...... guys, come here for a minute."

Jin called out to everyone present and headed for the bathroom.

He filled a large washtub with water,

"Look, watch carefully," he said.

and gently floated the boat with camphor on it in the water.

Then...

"Whoa!"

"Ah!"

The boat started to move.

"It's not magic ......, is it?

"No, I don't feel any magic."

"Then why is it moving?　...... Oh, maybe it's surface tension!"

Hannah is right.

This is a toy known in modern Japan as a "camphor boat.

It was occasionally seen at night stalls at fairs until around the late Showa period (1926-1989), but nowadays it is rarely seen because the distribution of camphor has drastically decreased with the rise of synthetic insect repellents.

"When camphor is dissolved in water, it lowers the surface tension.

"Oh, I knew it. So the surface tension of the water without camphor makes the boat move.

Hannah, who understood science better than anyone else, understood the principle and nodded her head repeatedly at Jin's explanation.

"That's right, any substance that has surfactant properties should work.

"So you can use soap?"

"Yes, you can. You can also put a dropper of alcohol in the back of the boat and it will work.

In a science experiment called "alcohol boat," a little more alcohol is dripped into the back of the boat with a soy sauce dropper, and the boat jumps out with great force.

The boat will jump out of the water.

"Oh, that was interesting.

"Hmm, that was interesting.

"Hmm, surfactant. It's very deep to study physical properties, isn't it?

The reactions of the members of the <> were generally favorable.

"So, we took a long way around..."

"In the end, Jin remembered the toy and wanted to make it.

Reinhardt hit the nail on the head.

"You're right."

"Ha, that's just like Jin."

But it was interesting.

"Hmm. Toys like this are interesting.

< echoing through the air.

* * * * * * * * * * * * * * *

"Should I say <>......<> at ......?　Did you find anything at ......?"

Jin asked Erza just as everyone was beginning to drink tea after the <> thing was over.

"Hmm, that's ......."

"What's wrong?"

"The information stored in that < was quite biased."

"I see. ...... how?"

"In a word, for beginners."

"Oh ......."

Elsa explained that there was some medical material, but it was all stuff she already knew.

She then had some extra time to look through the other materials, but found that they were all already in use, and some of them were obsolete and no longer in use.

"I didn't know that. ......"

Jin said regretfully,

"But we haven't gone through all of them yet," Elsa said consolingly.

Elsa said consolingly.

"Then, let's check that one together tomorrow, shall we?

"Yes, that sounds good."

"I hope we can find something useful, even if it's just one or two things."

"That's what I mean."

So, the next day, all the members of the in Horai Island decided to check the from one to another.