ulant shake as he realized this,
and was about to move away, when "Billy" Brackett, who sat on the end of
a log near him, spoke up and said,

"Glen, how would you like to try a bit of mountain climbing with me
to-morrow?"

"I'd like it better than anything I know of," answered the boy, eagerly.

"All right, it's a go, then; you see the chief is going off on an
exploration with the topographer; and, as we can't run any lines till he
comes back, he asked me if I'd take a couple of fellows and measure the
height of that peak."

"Do you mean to chain from here away up there?" asked Glen, in
astonishment, glancing dubiously up at the dim form towering above them.

"Chain! Not much, I don't!" laughed Brackett. "I mean carry up a
barometer, and measure with it."

"How?" asked Glen, to whom this was a novel idea.

"Easy enough. We know that, roughly speaking, a barometer varies a
little less than one tenth of an inch with every hundred feet of
elevation. For instance, if it reads 21.22 where we now are, it will
read 21.14 a hundred feet higher, or 20.40 at an elevation of a thousand
feet above this. There are carefully prepared tables showing the exact
figures."

"Can't you do it by boiling water, too?" asked Binney Gibbs, who had
approached them unobserved, and was an interested listener of this
explanation.

"Certainly you can," answered "Billy" Brackett, looking up with some
surprise at the young scholar. "By boiling water we have a neat check on
the barometer; for, on account of the rarefication of the air, water
boils at one degree less of temperature for about every five hundred
feet of elevation."

"Then what is the use of levelling?" asked Glen.

"Because these figures are only approximate, and cannot be relied upon
for nice work. But where did you learn about such things, Grip?"

"At the Brimfield High School," answered Binney with some confusion; for
he was not really so boastful of his scholarship as he had once been.

"Well, how would you like to join our climbing-party? I'm going to take
Glen along for his muscle, and I'll take you for your brains if you want
to go."

"I think I'd like to try it, though perhaps I won't be able to get to
the very top," answered Binney.

The modesty that this boy had learned from his rough Plains experience
would have surprised his Brimfield acquaintances could they have seen
it.

"Very well, then, we will start at sunrise in the morning. We'll each
carry a hatc