A point of far greater interest to Captain Servadac and his friends would have been to ascertain the nature of the substance of which the comet was composed, but they felt pledged to render the professor any aid they could in the researches upon which he had set his heart. Without delay, therefore, they assembled in the central hall, where they were soon joined by Rosette, who seemed to be in fairly good temper. “Gentlemen,” he began, “I propose to-day to endeavor to complete our observations of the elements of my comet. Three matters of investigation are before us. First, the measure of gravity at its surface; this attractive force we know, by the increase of our own muscular force, must of course be considerably less than that at the surface of the earth. Secondly, its mass, that is, the quality of its matter. And thirdly, its density or quantity of matter in a unit of its volume. We will proceed, gentlemen, if you please, to weigh Gallia.” Ben Zoof, who had just entered the hall, caught the professor’s last sentence, and without saying a word, went out again and was absent for some minutes. When he returned, he said, “If you want to weigh this comet of yours, I suppose you want a pair of scales; but I have been to look, and I cannot find a pair anywhere. And what’s more,” he added mischievously, “you won’t get them anywhere.” A frown came over the professor’s countenance. Servadac saw it, and gave his orderly a sign that he should desist entirely from his bantering. “I require, gentlemen,” resumed Rosette, “first of all to know by how much the weight of a kilogramme here differs from its weight upon the earth; the attraction, as we have said, being less, the weight will proportionately be less also.” “Then an ordinary pair of scales, being under the influence of attraction, I suppose, would not answer your purpose,” submitted the lieutenant. “And the very kilogramme weight you used would have become lighter,” put in the count, deferentially. “Pray, gentlemen, do not interrupt me,” said the professor, authoritatively, as if _ex cathedra_. “I need no instruction on these points.” Procope and Timascheff demurely bowed their heads. The professor resumed. “Upon a steelyard, or spring-balance, dependent upon mere tension or flexibility, the attraction will have no influence. If I suspend a weight equivalent to the weight of a kilogramme, the index will register the proper weight on the surface of Gallia. Thus I shall arrive at the difference I want: the difference between the earth’s attraction and the comet’s. Will you, therefore, have the goodness to provide me at once with a steelyard and a tested kilogramme?” The audience looked at one another, and then at Ben Zoof, who was thoroughly acquainted with all their resources. “We have neither one nor the other,” said the orderly. The professor stamped with vexation. “I believe old Hakkabut has a steelyard on board his tartan,” said Ben Zoof, presently.