THE SNOW-LINE.

"In three days the cart was finished. We had no difficulty in

constructing one, as the principal part--that is, the wheels--was

already made. We had two pair of them, of course, in our old wagon; and

the larger ones, which happened to be in very good order, served our

purpose exactly. Cudjo soon attached a body and shafts to them, and

Pompo's harness was put into thorough repair.

"We had not long to wait for a fine day. Every day was fine in the

clear, pure climate of our valley; so that, as soon as the cart was

ready, we had a day to our liking.

"We set out shortly after sunrise, with our hearts full of anticipated

pleasure. Of course we all went--Mary, the children, Cudjo, Pompo,

dogs, and all. The house was again left to take care of itself. Mary

and the two little ones rode in the cart, upon a soft seat made of

palmetto leaves and Spanish moss. Pompo, who appeared to partake of the

general happiness, whisked the vehicle along as if there had been nobody

in it, and he was only drawing it for his own amusement. Cudjo cracked

his great wagon-whip, and every now and then uttered a loud `wo-ha;'

while Castor and Pollux galloped gaily from side to side, running their

noses into every bush that grew near the path.

"We soon made our way through the valley, and climbed up to the plain.

We looked once more upon the Desert that stretched away on all sides;

but its dreary aspect no longer filled us with fear. We did not regard

it now, and the sight inspired us with feelings of curiosity and novelty

rather than of terror. Away to the southward the sun was glancing upon

the broad expanse of white sand; and several tall objects, like vast

dun-coloured towers, were moving over the plain. They were whirlwinds

carrying the dust upward to the blue sky, and spinning it from point to

point. Sometimes one glided away alone, until it was lost on the

distant horizon. Here two of them were moving in the same direction,

keeping a regular distance from each other, and seemingly running a

race. There several came together; and, after a short gusty contest,

the whole set would break up into shapeless masses of yellowish clouds,

and then float onward with the wind, and downward to the earth again.

It was an interesting sight to view those huge pillars towering up to

the heavens, and whirling like unearthly objects over the wide plain.

It was indeed an interesting sight, and we remained for many minutes

observing their motions.

"At length we turned our faces toward the mountain, and continued our

journey along the edge of the cliffs. The high peak glistened before

us, and the sun's rays falling upon it caused it to appear of a

beautiful colour--a mixture of gold and red, as though a shower of roses

had fallen upon the snow! We noticed that there was now more snow upon

the mountain than when we had first seen it, and that it came farther

down its sides. This attracted the attention of all of us; and Frank at

once called for an explanation, which his mother volunteered to give,

for she very well understood the phenomenon.

"`In the first place,' said she, `as you ascend upwards in the

atmosphere, it becomes thinner and colder. Beyond a certain point it is

so cold, that neither men nor any other animals can exist. This can be

proved in several ways; and the experience of those who have climbed

mountains, only three miles high, confirms it. Some of these

adventurous men have been nearly frozen to death. This is a fact, then,

in regard to the atmosphere over all parts of the earth; but we may also

observe, that under the Equator you may go higher without reaching this

extreme cold, than in the countries which lie nearer to the Poles.

Another fact, which you will easily believe, is, that in summer you can

climb higher before you reach the cold region than in winter. Bear

these facts in mind. Now, then, if it be so cold at a certain height

that men would be frozen to death, of course at that height snow will

not melt. What is the natural inference? Why--that mountains whose

tops pierce up into this cold region will most certainly be covered with

perpetual snow. It is not likely that anything but snow ever falls upon

their summits,--for when it rains upon the plains around them, it is

snowing upon the high peaks above. Indeed, it is probable that most of

the rain which descends upon the earth has been crystals of snow when it

commenced its descent; and, afterwards melting in the lower and warmer

regions of the atmosphere, takes the shape of water globules, and thus

falls to the ground. These globules, no doubt, are very small when they

first emerge from the snow region; but, as they pass slowly downward

through clouds of vapour, they gather together and attract others (by a

law which I have not time to explain); and, descending faster and

faster, at length plash down to the earth in large drops. Whenever it

rains, then, at any particular place, you may be almost certain that it

is snowing at the same time over that place--only at a point in the

atmosphere far above it. I have been convinced of this fact, by

observing that immediately after every occasion when it has rained in

the valley, there appeared a greater quantity of snow upon the mountain.

Had the mountain not been there, this snow would have continued on, and

become rain, like that which fell upon the plains, and into the valley.'

"`Then, mamma,' interrupted Frank, `this mountain must be of great

height, since the snow lies upon it all the year.'

"`Does that follow?'

"`I think so. You said the snow did not melt because it was cold high

up.'

"`But suppose you were in a country 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

speculation has arisen among cosmographers about the elevation of this

line. Of course, on mountains within the tropics this line will be at a

great height above the level of the sea. As you advance northward or

southward to the Poles, it will be found lower and lower, until within

the frigid zones it may be said to cease altogether--for there, as we

have said, snow covers the whole earth, and there can be no "snow-line."

"`From this, one would suppose that an exact scale might be formed,

giving the elevation of the snow-line for all latitudes. But that could

not be done. Observation has shown that it not only differs on

mountains that lie in the same latitude, but that on the same mountain

it is often higher on one side than the other--particularly on those of

great extent, as the Himmalehs of India. This is all quite natural, and

easily accounted for. The position of mountains to one another, and

their proximity or great distance from the sea, will give them a colder

or warmer atmosphere, independent of latitude. Moreover, the same

mountain may have a warmer climate on one side than the other; and of

course the snow-line will be higher on that side which is the warmer, in

consequence of the greater melting of the snow. This line, too, varies

in summer and winter for a like reason--as we see here upon our own

mountain, where it has already descended several feet since the weather

became colder. This, you will acknowledge, is all very natural; and you

will see, too, that Nature, although apparently capricious in many of

her operations, acts most regularly in this one, as perhaps in all

others.'

"`But, mamma,' inquired Harry, `can we not get to the top of the

mountain? I should like to have some snow to make snow-balls, and pelt

Frank with them.'

"`It would be a very difficult task, Master Hal; and more than either

you or I could get through with. I think Frank will escape being

snow-balled this time.'

"`But people have climbed to the top of the Himmaleh mountains; and they

are far higher than this, I am sure.'

"`Never,' interrupted Frank; `no one has ever climbed the Himmalehs.

Have they, mamma?'

"`No mortal has ever been so high as the summits of those great

mountains, which are more than five miles above the level of the ocean.

Even could they be climbed, it is not likely that any animal could live

at their top. These inaccessible things seem to have been designed by

the Creator to afford us objects for sublime contemplation--objects far

above the reach of mortal man, and that can never be rendered common by

his contact. Do they not seem so?'

"We had now reached the foot of the mountain, and halting near the

entrance of the ravine, we loosed Pompo from his cart, and rested

ourselves on the banks of the little stream. After a while we commenced

ascending up into the defile in search of the pinons. As we advanced,

Mary pointed out the trees which she had noticed on a former occasion.

They appeared of a light green colour, much lighter than others that

grew near them. We made towards one which stood apart, and was most

accessible to us. This we hoped might prove to be the bread-pine tree;

and we approached it with feelings of anxiety and expectation.

"In a short time we were under its branches; and if we had had no other

test than what we saw there, combined with the delicious fragrance of

the tree, we could have told that it could be no other than the pinon.

The ground was covered with cones, each of them about an inch and a half

in length; but on examining them, we found them all broken open and the

seed extracted. Some animal had been there before us, and relished

their contents--thus affording a proof that they were good to eat.

There were still many of the cones hanging on the tree; and it was not

long until we had split some of them open and tasted their ripe seeds.

"`It is it!' cried my wife, clapping her hands with delight. `It is the

nut-pine! This will serve for bread until we can grow our wheat and

corn. Come, let us gather them,' added she, pointing to a large grove

of the same trees that grew at a short distance; and we all hurried to

the grove, and commenced shaking down the cones and gathering them into

heaps.

"We had soon collected as many as we wanted, and in the evening we

returned to the valley, with our little cart half-full of pine-nuts. On

reaching home, some of them were parched and pounded into a sort of

coarse meal; and that night, for the first time during many weeks, we

had cakes to our supper.

The desert home · 第 57 / 92 题