try near the North Pole, where snow lies
all the year at the very sea-side, and consequently at the sea-level,
would it then prove a mountain to be very high?'

"`Oh! I see--I see now. The perpetual snow upon a mountain only shows
it to be of great height when the mountain happens to be in warm
latitudes.'

"`Precisely so. In very warm countries, such as those within the
tropics, when you see the snow-cap upon a mountain, you may infer that
it is a very high one--at least over two miles in height; and when there
is much snow upon it--that is, when the snow reaches far down its
sides--it proves the mountain to be still higher,--three miles or more
above the level of the ocean.'

"`Our mountain, then, must be a high one, since it is in a warm
latitude, and snow lies all the year upon it.'

"`It is a high one, comparatively speaking; but you will remember, when
we first saw it, there was only a small patch of snow upon its top, and
probably in very hot summers that disappears altogether; so that it is
not so high as many others upon this continent. Taking our latitude
into calculation, and the quantity of snow which lies upon this
mountain, I should say it was about 14,000 feet.'

"`Oh! so much as that! It does not seem half so high. I have seen
mountains that appeared to me to be quite as high as it, and yet it was
said they did not measure the half of 14,000 feet.'

"`That arises from the fact that you are not viewing this one from the
sea-level, as you did them. The plain upon which it stands, and from
which we view it, is of itself elevated nearly half as much. You must
remember that we are upon one of the high tables of the American
continent.'

"Here, for a minute or so, the conversation stopped; and we travelled on
in silence, all of us with our eyes fixed on the white and roseate peak
that glittered before us, leading our eyes far up into the heavens.

"Frank again resumed the discourse, which had been broken off by our
admiration of this beautiful object.

"`Is it not curious,' said he, `that the snow should lie so regularly,
coming down on all sides to the same height, and ending just like the
cape of a coat or the hem of a nightcap? It seems to be a straight line
all around the mountain.'

"`That line,' rejoined his mother, `is, as you say, a curious
phenomenon, and caused by the laws of heat and cold, which we have just
been explaining. It is called the "snow-line," and a good deal of
spe