Eureka! or rather Heureka! ("I have discovered it!") was the exclamation of Archimedes, the Syracusan philosopher, when he found out how to test the purity of Hiero's crown. The tale is that Hiero suspected that a craftsman to whom he had given a certain weight of gold to make into a crown had alloyed the metal, and he asked Archimedes to ascertain if his suspicion was well founded. The philosopher, getting into his bath, observed that the water ran over, and it flashed into his mind that his body displaced its own bulk of water. Now suppose Hiero gave the goldsmith one pound of gold, and the crown weighed one pound, it is manifest that if the crown was pure gold, both ought to displace the same quantity of water; but they did not do so, and therefore the gold had been tampered with. Archimedes next immersed in water one pound of silver, and the difference of water displaced soon gave the clue to the amount of alloy introduced by the artificer.

The phenomenon known as the blizzard is a fierce storm of bitter, frosty wind with blinding snow, in which, especially in the western States, man and beast often perish. The word seems to be akin to blast and bluster and is no doubt onomatopoetic in character. The most severe of record is the one that visited the Dakotas, Montana, Minnesota, Nebraska, Kansas and Texas in January, 1888. Within twenty-four hours the thermometer fell from 74° above zero to 28° below zero in most places and in Dakota to 40° below. The roar of the wind drowned the voices of men six feet distant. Objects a few yards off became invisible. Some two hundred and thirty-five lives were lost. The Colorado river in Texas for the first time in the memory of man was covered with ice a foot thick.

Such fierce canivorous fishes as exist in the depths of the ocean are unknown at the surface. There is the "black swallower," which devours other finny creatures ten times as big as itself, literally climbing over its victim, first with one jaw and then with the other. Another species is nearly all mouth, and having no power of locomotion, it lives buried in the soft ooze at the bottom, its head alone protruding, ready to engulf any prey that may wander into its cavernous jaws. There is a ferocious kind of shark, resembling a huge eel. All of these monsters are black as ink. Some of them are perfectly blind, while others have enormous goggling eyes. No ray of sunlight ever pierces the dark unfathomed caves in which they dwell. Each species is gobbled by the species next bigger, for there is no vegetable life to feed on.

On metal rails a horse can draw:

One and two-thirds times as much as on asphalt pavement.

Three and one-third times as much as on good Belgian blocks.

Five times as much as on ordinary Belgian blocks.

Seven times as much as on good cobble-stone.

Thirteen times as much as on ordinary cobble-stone.

Twenty times as much as on an earth road.

Forty times as much as on sand. A modern compilation of engineering maxims states that a horse can drag, as compared to what he can carry on his back, in the following proportions: On the worst earthen road, three times more; on a good macadamized road, nine; on plank, twenty-five; on a stone trackway; thirty-three; and on a good railway, fifty-four times as much.

Whirlwinds occurring on the sea and other sheets of water are called waterspouts. When fully formed they appear as tall pillars of cloud stretching from the sea to the sky, whirling round their axes, and exhibiting the progressive movement of the whole mass precisely as in the case of the dust-whirl-wind. The sea at the base of the whirling vortices is thrown into violent commotion, resembling the surface of water in rapid ebullition. What are sometimes called "waterspouts on land" are quite distinct phenomena. They are merely heavy falls of rain of a very local character, and may or may not be accompanied with whirling winds. They generally occur during thunderstorms, being quite analogous to severe hailstorms, from which they differ only in point of temperature, the heavy drops being probably no more than melted hailstones. Also all the moisture that falls is the result of condensation; whereas, in the true waterspout, the rain is mixed with spray which has been caught up from the broken waves, carried aloft by the ascending currents of the whirlwind, and ultimately precipitated with the rain.

Hypnotism is a method for the alleged cure of disease, by the concentrated action of the mind upon the body while in a state of trance, induced by causing the patient to fix his eyes and concentrate his mind upon a disc of bright metal held at a distance of about twelve inches above the level of the eyes. The first effort to investigate hypnotism in a scientific manner was made by James Braid, of Manchester (1846) from which circumstance hypnotism is sometimes called Braidism. The power to hypnotize is possessed only by persons of peculiar mental organization. While in the hypnotized condition, which renders them insensible to pain, patients may be operated upon for surgical or medical purposes, the patient being entirely subject to the will of the hypnotizer. Hypnotism can, however, only be considered as of quasi medical utility, though investigation is being made with the view to placing it on a sound scientific basis.

The Copernican system is that which represents the sun to be at rest in the center of the universe, and the earth and planets to move round it as a center. It got its name from Copernicus, who (although some vague general notion of the system seem to be due to Pythagoras) first distinctly drew the attention of philosophers to it, and devoted his life to its demonstration. For the rest, the glory of developing on the lines he broadly laid down, belongs to Kepler, Galileo and others, and to Newton who finally marked out the form of modern theoretical astronomy. Many who reverence the name of Copernicus in connection with this system, would be surprised to find, on perusing his work, how much of error, unsound reasoning, and happy conjecture combined to secure for him in all times the association of the system with his name; yet, with all its faults, that work marks one of the greatest steps ever taken in science.