strait by a rapid tide; meeting, as mountains in motion would meet, with a noise like thunder; breaking from each other's precipices huge fragments, or rending each other asunder, till, losing their former equilibrium, they fall over headlong, lifting the sea around in breakers, and whirling it in eddies; whilst the flatter fields of ice, forced against these masses, or against the rocks, by the wind and the stream, rise out of the sea till they fall back on themselves, adding to the indescribable commotion and noise which attend these concussions. The strongest ships can no more withstand the contact of two ice-fields than a sheet of paper can stop a musket ball.

"It is far, however, from being an unmixed evil; and estimating all our adventures with and among it, I might not be wrong in saying, that it had been much oftener our friend than our enemy... We could not, indeed, command the icebergs to tow us along, to arrange themselves about us so as to give us smooth water in the midst of a raging sea; nor, when we were in want of a harbor, to come to our assistance, and surround us with piers of crystal, executing in a few minutes works as effectual as the breakwaters of Plymouth or Cherbourg; but they were commanded by Him who commands all things, and they obeyed."

Few sights in nature are more imposing than that of the huge solitary iceberg, as, regardless alike of wind and tide, it steers its course across the face of the deep far away from land. Like one of the Frost-giants of Scandinavian mythology, it issues from the portals of the north armed with great blocks of stone... Proudly it sails on. The waves that dash in foam against its sides shake not the strength of its crystal walls, nor tarnish the sheen of its emerald caves. Sleet and snow, storm and tempest, are its congenial elements... Night falls around, and the stars are reflected tremulously from a thousand peaks, and from the green depths of "caverns measureless to man." Dawn again arises, and the slant rays of the rising sun gleam brightly on every projecting crag and pinnacle, as the berg still floats steadily on; yet, as it gains more southern latitudes, what could not be accomplished by the united fury of the waves, is slowly effected by the mildness of the climate... The floating island becomes gradually shrouded in mist and spume, streamlets everywhere trickle down its sides, and great crags ever and anon fall with a sullen plunge into the deep. The mass becoming top-heavy, reels over, exposing to light rocky fragments still firmly imbedded. These, as the ice around them gives way, are dropped one by one into the ocean, until at last the iceberg itself melts away, the mists are dispelled, and sun

shine once more rests upon the dimpled face of the deep... If, however, before this final dissipation, the wandering island should be stranded on some coast, desolation and gloom are spread over the country for leagues. The sun is obscured, and the air chilled; the crops will not ripen; and, to avoid the horrors of famine, the inhabitants are fain to seek some more genial locality until the ice shall have melted away; and months may elapse before they can return again to their villages

The iceberg melts away, but not without leaving wellmarked traces of its existence. If it disappear in mid-ocean, the mud and boulders, with which it was charged, are scattered athwart the sea-bottom. Blocks of stone may thus be carried across profound abysses, and deposited hundreds of miles from the parent hill; and it should be noticed, that this is the only way, so far as we know, in which such a thing could be effected.

Great currents could sweep masses of rock down into deep gulfs, but could not sweep them up again, far less repeat this process for hundreds of miles. Such blocks could only be transported by being lifted up at the one place and set down at the other; and the only agent we know of capable of carrying such a freight, is the iceberg. In this way, the bed of the sea in northern latitudes must be covered with a thick stratum of mud and sand, plentifully interspersed with boulders of all sizes, and its valleys must gradually be filled up as year by year the deposit goes on... But this is not all. The visible portion of an iceberg is only about one-ninth part of the real bulk of the whole mass, so that if one be seen 100 feet high, its lowest peak may perhaps be away down 800 feet below the waves. Now it is easy to see that such a moving island will often grate across the summit and along the sides of submarine hills; and when the lower part of the berg is roughened over with earth and stones, the surface of the rock over which it passes will be torn up and dispersed, or smoothed and striated, while the boulders imbedded in the ice will be striated in turn... But some icebergs have been seen rising 300 feet over the sea; and these, if their submarine portions sank to the maximum depth, must have reached the enormous total height of 2700 feetthat is, rather higher than the Cheviot Hills. By such a mass, any rock or mountain-top existing 2400 feet below the surface of the ocean would be polished and grooved, and succeeding bergs depositing mud and boulders upon it, this smoothed surface might be covered up and suffer no change until the oceanbed should be slowly upheaved to the light of day...In this way, submarine rock surfaces at all depths, from the coast line down to 2000 or 3000 feet, may be scratched and polished, and

eventually entombed in mud. And such has been the origin of the deep clay, which, with its accompanying boulders, covers so large a part of our country.

When this arctic condition of things began, the land must have been slowly sinking beneath the sea; and so, as years rolled past, higher and yet higher zones of land were brought down to the sea-level, where floating ice, coming from the north-west, stranded upon the rocks, and scored them all over as it grated along. This period of submergence may have continued until even the highest peak of the Grampians disappeared, and, after suffering from the grinding action of icefreighted rocks, eventually lay buried in mud far down beneath a wide expanse of sea, over which there voyaged whole argosies of bergs.

When the process of elevation began, the action of waves and currents would tend greatly to modify the surface of the glacial deposit of mud and boulders, as the ocean-bed slowly rose to the level of the coast-line. In some places the muddy envelope was removed, and the subjacent rock laid bare, all polished and grooved. In other localities, currents brought in a continual supply of sand, or washed off the boulder mud and sand, and then re-deposited them in irregular beds; hence resulted those local deposits of stratified sand and gravel so frequently to be seen resting over the boulder clay... At length, by degrees, the land emerged from the sea, yet glaciers still capped its hills and choked its valleys; but eventually, a warmer and more genial climate arose, plants and animals, such as those at present amongst us, and some, such as the wolf, no longer extant, were ere long introduced; and eventually, as lord of the whole, man took his place upon the scene. Geikie.

PHYSICS.

PROPERTIES OF MATTER.

WHATEVER fills space we call matter. In a loose way of speaking, we may say that matter is the substance of which everything in the universe is made. When matter is limited in any way, so as to form but one thing, we sometimes speak of it as a body or object... If we think a little about this property of filling space which belongs to all matter, we shall easily be led to see that no two bodies can possibly occupy the same space at the same time. A dog and a tree cannot both stand at once in the very same spot. The teaspoon which we put into our tea seems only to be in the same place as our tea; before it gets down to the bottom of the cup, it must necessarily push back the particles of the liquid, which are easily movable, and make the tea stand higher in the cup... So a nail only seems to be in the same place with the bit of wood in which it is; as it is driven in, it pushes the particles of wood on each side of it, in order that they may make room for it. This property of matter we call impenetrability.

It is quite impossible for us to think of anything which has not some size and some shape; size and shape then are said to be essential properties of matter.

Grains

Again, any body, or quantity of matter, may be divided, or separated into parts by the application of proper means. of corn are ground into flour: metals are beat into thin leaves, or ground to glittering dust; or they may be drawn into wires so fine that 140 of them put together are no thicker than a single silk thread. This property of matter we call divisibility. ...It is wondrous to think how far divisibility may be carried. A soap bubble is only a thin film made of water and soap, and does not exceed in thickness the 2,500,000th part of an inch. It has been ascertained, by a celebrated philosopher, that it would require 4,000,000 of the threads of a gossamer spider to be as thick as a common hair. Animalcules, that is, animals too small to be seen by the naked eye, but which are seen by

microscopes, are some of them so small that a million of them heaped together would be no bigger than a grain of sand. What then must be the size of the organs in the bodies of these animals!

The cause of our smelling anything, such as a rose, or eau de Cologne, is its sending off continually into the air extremely small particles, which affect our noses. Now a single grain of musk has been known to perfume a room for twenty years, and then it appeared no smaller than at first. How small indeed must these particles have been, which continued to spread themselves through the whole of the room for twenty years, without apparently reducing the size of the musk!

In speaking of this property of matter, there is one truth which should not be forgotten;-namely, that nothing is ever destroyed or lost. What we are in the habit of calling destruction is only change. The candle burns away to nothing— so it seems at least; but the chemist knows better, and can prove that its particles have only been divided and changed. Part of it has gone into vapor, part into the ashes which remain; and it is possible so to burn the candle, that all the parts could be again collected. They would then, in their new shape, be found to weigh just as much as the candle did before being lighted. Even what we call the corruption of the human body is only a change of all its parts into new forms, which continue fulfilling other purposes in nature.

There is another property of matter expressed by the word inertia. This word represents two facts respecting matter, -namely, that when a body is at rest it will remain so, unless moved by something else; and when it is in motion, it will continue to move for ever unless something else stops it. It would never stop of itself... Some consequences of this property are interesting. I dare say some of you have been in a railway carriage when it was starting: perhaps it started before you expected it, and backwards you went against the wooden wall of the carriage, a little to the detriment of your head the carriage moved, and took your feet, which were on the floor, with it; but your body being at rest tended to remain at rest: it was therefore left behind, and caused you to tumble backward... On the other hand, when the carriage pulls up suddenly, if you are not watching, you suffer in a contrary direction you fall forward, to the detriment of your nose. The carriage stops; the portion of your body in contact with it, stops too; but your head and shoulders, being free and in motion, tend to remain in motion. They go forward, and you tumble. Similarly, when a ship strikes a rock suddenly,