but how this sound is propagated, I do not see."

"Very likely; but still it travels from particle to particle, in a
circle, at the rate of three hundred and forty yards in a second."

"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