rocks. The place was very near the crest of the crater, and the people
that stood around it were watching to see men cook in the jets of steam.
There was a little level place inside the crevice, just beneath the
ground, where they could put eggs and other such things, and after
leaving them there a short time, they were found to be nicely cooked. As
fast as they were done, the men took them out and sold them to the
bystanders.

Mr. George left Rosie and the two boys here while he went down into the
crater. The guide went with him to show him the way. In about ten
minutes Mr. George returned, and found the three children standing round
the _cuisine_, as the men called the place where they cooked. Rollo had
been buying some of the eggs, and he and Josie and Rosie were eating
them.

"Mr. George," said Josie, "are these boiled eggs, or baked eggs, or
roasted eggs, or what?"

"They seem to be steamed eggs," said Mr. George.

"I suppose," said Rollo, "that by digging about here in the sand, we
might find a place where it would be just warm enough to _hatch_ eggs."

"No doubt," said Mr. George.

Just then Rollo observed that the two young men whom he and Josie had
followed down into the crater were standing at a little distance, and
attentively regarding some sort of instrument which they had in their
hands.

"I mean to go and see what they are doing," said Rollo.

So saying, he looked into Mr. George's face, and waited to see if Mr.
George had any objection to his going.

"Very well," said Mr. George.

So Rollo went off to the place where the young men were standing, and
soon afterwards Mr. George and the others of the party could see that
the strangers were showing him the instrument, and apparently explaining
it to him. Pretty soon Rollo returned and reported that the two young
men were students, and that the instrument which they had was a metallic
barometer, and that they were measuring the height of the mountain with
it.

This metallic barometer is quite a curious instrument. You will often
read, in books, of measuring the height of a mountain, or other lofty
place, _by the barometer_; and to most people this is quite a mystery.
The explanation of it is, however, very simple. It is this: The earth is
surrounded on all sides by the atmosphere, which, though very light,
has a certain weight, and it presses with considerable force upon the
ground, and upon every thing that is exposed to it. If, however, you go