In England are several interesting waterfalls, and amongst others may be mentioned that on the river Tees in the county of Durham; the cataract of Lodore on the Derwentwater in Cumberland, which Southey has immortalised; that of Sty Head in Borrowdale, which is about 800 feet high; and that on the river Lyd in Devonshire, which has been thus described by a traveller who had visited the spot. "Not far from Lydford is what is commonly, but erroneously, called Lyd fall, which is occasioned, not by the river, but by the collection of several rivulets above into an excavated space for the use of a mill, whose waters united into a single stream form the fall, and which are sometimes ponded back to produce a greater effect on the eye of strangers. The rock over which the waters glide is composed of smooth schistose strata, and some way down is a projection, which causes, as it were, a second fall. At the bottom, to which there is a winding path through a wood, is a cauldron or pit, hollowed by the constant attrition. The height of the fall, or rather of the two falls, may be estimated at 110 feet. The Lyd, emerging into day from the chasm, joins the falling waters, and both flow together in a more peaceable course down the valley, the sides of which are roughened with woods and copses. The depth of the valley, and the gloom diffused by the thick woods, give solemnity to the scene, which would amply repay the traveller who may be fond of picturesque scenery, even if there were no waterfall to increase the beauty or add to the other natural attractions of the place. The Lyd likewise forces its silvery stream through the wood, and gives additional beauty to this interesting spot." "On the Lyd is another fall, called Kit or Skid fall, on a common a mile and a half from the castle. The river here bursts through steep and craggy rocks, with a descent of thirty feet, at one place losing itself beneath the stones. If surrounded by trees, it would be still more attractive than it is, but still it highly deserves a visit. Fragments of tin ore are frequently found in the channel of the Lyd."
Whirlpools are when two opposite currents of nearly equal force meet, especially in narrow channels, when they sometimes assume a spiral direction. The most celebrated whirlpool in the world is that of Maelström on the coast of Norway; but it is only at certain seasons that it is dangerous. When the flood-tide sets in from the south-west, and it meets a strong gale from the north-west, the whirlpool is formed, and its roaring is heard at the distance of many miles. It is not only dangerous to vessels, but it is said that seals and whales, if caught in its eddies, cannot possibly escape. The water of the whirlpool is said to be forty fathoms deep; and at the ebbing of the tide its noise is as loud as a cataract. In 1645 it was so violently agitated by a storm, that some of the stones of the houses in the adjoining Isle of Moskoe were shaken out of their places, and fell to the ground. "Fragments of vessels wrecked in the Maelström are frequently seen on the coast, brought up by the return of the tide, their edges mashed and jagged as if with a saw, which would induce the belief that the bottom is composed of sharp rocks."
CHAPTER VI. ICEBERGS AND ICEFIELDS.
Though it was formerly supposed that salt water could never freeze, it is a well known fact, that large masses of floating ice are frequently met with in the seas of the high northern latitudes. To account for this, it is said that the snow on the land adjoining the North Seas freezes till it becomes a solid mass of ice, which is continually being increased by fresh snow being deposited upon it. "When such a mass has reached the height of 1000 or 2000 feet, the accumulated weight, assisted by the action of the ocean at its base, plunges it into the sea, and it is driven southwards by the winds and currents, and known to mariners under the name of an iceberg. The icebergs consist of a clear, compact, solid ice, with a bluish-green tint; and from the cavities in them, the northern whalers fill their casks with pure fresh water."
On the other hand, what is called field ice, being frozen sea-water, is porous and incompact; as it is composed of thin flakes, which contain salt within their interstices. Common water, as is known, freezes at 32°, but sea-water will not congeal till the thermometer is at 27°, that is, five degrees colder. A large expanse of saline ice is called a field, and one of smaller dimensions a floe; but when the floe ice is much broken it is denominated a pack. If a ship can sail freely through the floating pieces of ice, these pieces are called drift ice; but if they rise above the common level, and then freeze together, the mass is called a hummock. What is called the ice blink has a whitish appearance in the horizon, occasioned by fields of ice reflecting the light obliquely against the atmosphere. Very serious damage has been frequently done to ships by icebergs and fields of ice; and the appearance of icebergs and hummocks in the water has been described as most extraordinary. In some cases the hummocks are produced by two pieces of ice being driven forcibly together; so that the edges of the ice are broken, and forced upwards, though still pushing against each other, while in this position they are again frozen. When this is the case, the colours produced by the refraction of light on the ice are very striking.
The icebergs are like enormous floating hills composed of rugged and steep rocks. They have been seen of various sizes, but they are generally from fifty to 120 feet above the level of the water; and, as they are of enormous width, when a current forces them against a ship, the effects are generally fatal. Sometimes the field ice is equally as injurious as the icebergs, particularly when the field of ice is what is called heavy, that is, of considerable extent; as the sharp edge of the ice, when forced by the current against a vessel, comes with such violence, as to cut through the solid timber. In April, 1841 the Great Western had considerable difficulty in extricating herself from an icefield which extended for more than 100 miles in a direction from east to west; and on the 21st of May, 1847, the packet ship Eulalia, while on her passage from Havannah to Galway, was overwhelmed by an iceberg.
ICEBERGS.
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Early in the morning she met with a heavy field of ice, which the master attempted to clear, but this was found impossible, and about nine o'clock a tremendous iceberg struck the ship amidships, cutting her down to the water's edge. There were thirty-seven passengers, many of whom were women, on board, and a crew of sixteen persons including the master. The moment the ship was struck, the boats were lowered, and two of them, containing the captain, fourteen of the crew, and fourteen passengers, succeeded in getting clear of the wreck; but the third, with upwards of twenty persons in it, principally women, was drawn down by the vessel, and every human being perished. The boat, it appeared, was fastened to the wreck by a rope, which the crew, in their fright, fearing the ship was sinking, had forgotten to unfasten, and which it was impossible to cut, the passengers having no implement with them.
At all times the navigation among ice fields and ice floes is attended with considerable danger. "The fields frequently have a rotatory movement: which appears to be produced by the different force with which the current acts on the different sides of such a large body of ice. By this movement their outer borders acquire a velocity of several miles per hour. A field thus in motion coming in contact with another at rest, or, as it at times happens, with one which has a contrary direction of movement, produces a dreadful shock. It is easy to comprehend that a body of more than 10,000,000,000 of tons in weight, meeting with resistance when in motion, produces effects which it is scarcely possible to conceive. The weaker field is crushed with an awful noise; and sometimes the destruction is mutual." That a ship placed between the two fields would be destroyed, is easily to be imagined; and, in fact, numbers of whalers have been destroyed in this way. In the year 1804, Captain Scoresby met with an accident of this kind, which he has thus described in his Account of the Arctic Regions. "Passing between two fields of ice newly formed, about a foot in thickness, they were observed rapidly to approach each other, and before our ship could pass the strait, they met with a velocity of three or four miles per hour. The one overlaid the other, and presently covered many acres of surface. The ship proving an obstacle to the course of the ice, it was squeezed up on both sides, the blow shaking her in a dreadful manner, and producing a loud grinding or lengthened acute tremulous noise, according as the degree of pressure was diminished or increased, until it had risen as high as the deck. After about two hours the motion ceased, and soon afterwards the two sheets of ice receded from each other nearly as rapidly as they had before advanced. The ship in this case did not receive any injury, but had the ice been only half a foot thicker, she might have been wrecked." In other cases ships become surrounded by drift ice in such a manner that they can neither advance nor recede, but are literally frozen up. This has frequently happened, and is supposed by some persons even now to be the case with the expedition under Sir John Franklin. In other cases ships have been beset with ice, which has frozen round them, so that the ship has assumed the appearance of an iceberg, and has drifted with the current just as a quantity of solid ice would have done.
ATMOSPHERIC PHENOMENA.
It is a very common mistake to suppose that the whole space which intervenes between our planet and the other celestial bodies is filled with what we call the atmosphere. This is by no means the case: the atmosphere is a transparent covering which belongs to the earth and moves with it, and which has been compared to the coats of varnish laid on a common painted globe; as, though the extent of the atmosphere is supposed to be about forty-six miles from every part of the surface of the earth, this thickness is not more, when compared with the size of the globe, which is about 8000 miles in diameter, than the coats of varnish are to the artificial globe. The atmosphere, or air, which thus surrounds the globe, is an elastic fluid, capable of either compression or distension; and, as every square foot of earth has to support the weight of a column of air of the same diameter, forty-six miles in height, it is easy to imagine that the stratum of air which lies next the earth is more compressed, or, in other words, is rendered more dense than the stratum of air immediately above it; and that the strata of air will be less compressed, or, in other words, become more rarefied, in proportion as they recede from the earth, and as the column of air above each becomes shorter and consequently lighter. Air is composed of a combination of different gases; and the air we breathe generally consists of about seventy-nine parts of nitrogen, twenty of oxygen, and one of carbonic acid. Occasionally these gases are mixed with a vapour, or steam of water rising from the earth, which consists of hydrogen and oxygen. Air possesses the property of refracting light, that is of bending it from a right line and making it move in a curve. The consequence of this is, that the sun continues visible to us a short time after it sets, and appears to us a short time before it rises; and hence also arise many other optical delusions in the atmosphere. The higher strata of air are very inflammable, and hence shooting stars, fire balls, and other meteors appear to be formed in those regions. It has been already observed that moisture is continually mixing with the air, part of which rises from the earth in the shape of vapour; and as the globules of water which thus rise have a tendency to congregate together, they form, while suspended in the air, what are called clouds; and when the water contained in these clouds becomes too heavy to be supported by the column of air beneath it, it descends upon the earth in the shape of rain. When the earth is cold, and the air surcharged with moisture, the vapour from the earth hovers on the tops of the hills, and spreads over the valleys instead of forming clouds, and when this is the case it becomes what we call a fog. When the earth is much colder than the air, the rain in descending becomes hail, and when the strata of air, through which the rain has to descend, are colder than the clouds, the rain becomes snow.