The measurement thus obtained was by means of a pair of compasses divided accurately into ten equal portions, or decimeters, each of course 3.93 inches long. A lath was then cut of this exact length and given to the engineer of the _Dobryna_, who was directed to cut out of the solid rock the cubic decimeter required by the professor.

The next business was to obtain the precise weight of a kilogramme. This was by no means a difficult matter. Not only the diameters, but also the weights, of the French coins are rigidly determined by law, and as the silver five-franc pieces always weigh exactly twenty-five grammes, the united weight of forty of these coins is known to amount to one kilogramme.

"Oh!" cried Ben Zoof; "to be able to do all this I see you must be rich as well as learned."

With a good-natured laugh at the orderly's remark, the meeting adjourned for a few hours. By the appointed time the engineer had finished his task, and with all due care had prepared a cubic decimeter of the material of the comet.