“Three hundred and forty yards in a second!” said Willis, who was beginning by degrees to recover his self-possession.  “Well, that is what I should call going a-head.”

“And by what sort of compasses has this speed been measured, Master Ernest?”

“The first accurate measurement, Master Jack, was made at Paris in 1738.  There are there two tolerably elevated points, namely, Montmartre and Montlhery—­the distance between these, in a direct line, is 14,636 toises.  Cannons were fired during the night, and the engineers on one of the elevations observed that an interval of eighty-six seconds and a half elapsed between the flash and the report of a cannon fired on the other.”

“That half-second is very amusing,” said Jack laughing; “if there had been only eighty or eighty-six net, one might still be permitted to entertain some doubts; but eighty-six and a half admits nothing of the kind.  But why not three-quarters or six-eighths, they would do as well?”

“What is more natural than to reckon the fraction, if we are desirous of obtaining absolute precision?  Is six months of your time of no value?  Are thirty minutes more or less on the dial of your watch of no signification to you?”

“Your brother is perfectly right, Jack; you are not always successful in your jokes.”

“Other experiments have been made since then,” continued Ernest, “and the results have always been the same, making allowances for the wind, and a slight variation that is ascribed to temperature.”

“To confirm the accuracy of this statement, the speed of light would have to be taken into consideration.”

“True; but the velocity of light is so great, that the instant a cannon is fired the flash is seen.”

“Whatever the distance?”

“Yes, whatever the distance.  Bear in mind that the rays of the sun only require eight minutes to traverse the thirty-four millions of leagues that extend between us and that body.  Hence it follows that the time light takes to travel from one point to another on the earth may be regarded as nil.”

“That is something like distance and speed,” remarked Willis, “and may be all right as regards the sun, but I should not be disposed to admit that there are any other instances of the same kind.”

“Very good, Master Willis; and yet the sun is only a step from us in comparison to the distance of some stars that we see very distinctly, but which are, nevertheless, so remote, that their rays, travelling at the same rate as those of the sun, are several years in reaching us.”

Willis rose abruptly, whistling “the Mariner’s March,” and went to join Fritz, who was steering the pinnace.

At this naive mark of disapprobation on the part of the Pilot, Becker, Ernest, and Jack burst involuntarily into a violent peal of laughter.

“Laugh away, laugh away.” said Willis; “I will not admit your calculations for all that.”