“Our curiosity will be gratified,” said Servadac, “if you will enlighten our ignorance.”
But Rosette did not take the slightest notice of the interruption.
“A substance it is which no doubt constitutes the sole material of the comet, extending from its surface to its innermost depths. The probability is that it would be so; your experience confirms that probability: you have found no trace of any other substance. Of this rock here is a solid decimeter; let us get at its weight, and we shall have the key which will unlock the problem of the whole weight of Gallia. We have demonstrated that the force of attraction here is only one-seventh of what it is upon the earth, and shall consequently have to multiply the apparent weight of our cube by seven, in order to ascertain its proper weight. Do you understand me, goggle-eyes?”
This was addressed to Ben Zoof, who was staring hard at him. “No!” said Ben Zoof.
“I thought not; it is of no use waiting for your puzzle-brains to make it out. I must talk to those who can understand.”
The professor took the cube, and, on attaching it to the hook of the steelyard, found that its apparent weight was one kilogramme and four hundred and thirty grammes.
“Here it is, gentlemen; one kilogramme, four hundred and thirty grammes. Multiply that by seven; the product is, as nearly as possible, ten kilogrammes. What, therefore, is our conclusion? Why, that the density of Gallia is just about double the density of the earth, which we know is only five kilogrammes to a cubic decimeter. Had it not been for this greater density, the attraction of Gallia would only have been one-fifteenth instead of one-seventh of the terrestrial attraction.”
The professor could not refrain from exhibiting his gratification that, however inferior in volume, in density, at least, his comet had the advantage over the earth.
Nothing further now remained than to apply the investigations thus finished to the determining of the mass or weight. This was a matter of little labor.
“Let me see,” said the captain; “what is the force of gravity upon the various planets?”
“You can’t mean, Servadac, that you have forgotten that? But you always were a disappointing pupil.”
The captain could not help himself: he was forced to confess that his memory had failed him.
“Well, then,” said the professor, “I must remind you. Taking the attraction on the earth as 1, that on Mercury is 1.15, on Venus it is .92, on Mars .5, and on Jupiter 2.45; on the moon the attraction is .16, whilst on the surface of the sun a terrestrial kilogramme would weigh 28 kilogrammes.”
“Therefore, if a man upon the surface of the sun were to fall down, he would have considerable difficulty in getting up again. A cannon ball, too, would only fly a few yards,” said Lieutenant Procope.
“A jolly battle-field for cowards!” exclaimed Ben Zoof.
“Not so jolly, Ben Zoof, as you fancy,” said his master; “the cowards would be too heavy to run away.”
Ben Zoof ventured the remark that, as the smallness of Gallia secured to its inhabitants such an increase of strength and agility, he was almost sorry that it had not been a little smaller still.
“Though it could not anyhow have been very much smaller,” he added, looking slyly at the professor.
“Idiot!” exclaimed Rosette. “Your head is too light already; a puff of wind would blow it away.”
“I must take care of my head, then, and hold it on,” replied the irrepressible orderly.
Unable to get the last word, the professor was about to retire, when Servadac detained him.
“Permit me to ask you one more question,” he said. “Can you tell me what is the nature of the soil of Gallia?”
“Yes, I can answer that. And in this matter I do not think your impertinent orderly will venture to put Montmartre into the comparison. This soil is of a substance not unknown upon the earth.” And speaking very slowly, the professor said: “It contains 70 per cent. of tellurium, and 30 per cent. of gold.”
Servadac uttered an exclamation of surprise.
“And the sum of the specific gravities of these two substances is 10, precisely the number that represents Gallia’s density.”