In Mercator's Projection the maps are so constructed that the lines of longitude are straight and not curved. This device of representing a globe in perspective on a flat surface is due to Edward Wright, an Englishman; but the chart so arranged by Wright was printed and published by Gerard Mercator, a printer of maps in Flanders, who died at the age of eighty-two, in 1594.

Those who use pencils should know that "black lead" is but the popular name for plumbago, a mineral consisting chiefly of carbon, together with alumina, silica, lime, iron, etc. No lead whatever enters into its composition. It is employed in making pencils, to give a black gloss to iron grates, railings, etc., and to diminish the friction of belts, machinery and rifle cartridges.

An English rainmaker operating in India has an apparatus consisting of a rocket capable of rising to the height of a mile, containing a reservoir of ether. In its descent it opens a parachute, which causes it to come down slowly. The ether is thrown out in a fine spray, and its absorption of heat is said to lower the temperature about it sufficiently to condense the vapor and produce a limited shower.

The greatest known depth of the ocean is midway between the islands of Tristan d'Acunha and the mouth of the Rio de la Plata. The bottom was here reached at a depth of 46,236 feet, eight and three-fourths miles, exceeding by more than thirteen thousand feet the height of Mt. Hercules, the loftiest mountain in the world. The average depth of all the oceans is from two thousand to three thousand fathoms.

It is a rare thing to find a really lustrous pearl in an American oyster, but a great many such pearls are found in the common fresh-water mussel. The pearl-bearing mussel is distributed over a wide area in the United States, and extremely valuable mussel pearls have been found in New Jersey, Ohio, Tennessee and several other states. An occasional black pearl of some value is found in the native oyster.

The Davy lamp is a form of safety lamp for use in coal mines, in-vented by Sir Humphry Davy in 1815. In it the frame is surrounded with fine wire gauze, on the principle that flame will not pass through the holes, and so does not ignite the gas surrounding the lamp. George Stephenson invented a similar lamp, but both are now largely susperseded by the use of electric lights in mines.

With the aid of the great Lick telescope the astronomers in charge of that institution have made the startling discovery that one of the satellites of Jupiter is double- in other words, that what has heretofore been taken for a single moon is, indeed, two moons, a large and a small one, the lesser slowly revolving around the greater. Hereafter it will be proper to speak of the "twenty-one moons of the solar system."

The word comet is derived from the Greek koine, "hair," a title which had its origin in the hairy appearance often exhibited by the haze or luminous vapor, the presence of which is at first sight the most striking characteristic of the celestial bodies called by this name. The general features of a comet are- a definite point or nucleus, a nebulous light surrounding the nucleus, and a luminous train preceding or following the nucleus.

Nectar in flowers is not honey. This nectar is gathered by the tongue of the bee, and enters what is called the honey bag, from which it is regurgitated by the bee on its return to the hive, and deposited in the honey cell. Even then it is thin and watery, and does not become really honey until the watery parts have evaporated. In collecting the sweets the bees do not confine themselves wholly to flowers. They extract them also from fruits.

According to the theory of evolution, the lower animals develop into the higher animals, so that the larvae of Ascidians (marine molluscoid) developed gradually into apes, and probably apes are only one link from man; but hitherto no trace of that link has been discovered, unless, indeed, it be in the Neanderthal skull found in the Rhine province of Russia, which seems to be between the skull of an ape and the skull of a human being.

Several meanings attach to the word Degree. (1.) The highest part of an unknown quantity in algebra. (2.) The three hundred and sixtieth part of a circle, as of the circumference of the earth, the length being sixty-nine and one-half miles at the equator. - Academicat D. A distinction conferred by the various universities in recognition of proficiency in arts, medicine, law and science. There are three degrees: Bachelor, Master and Doctor.

The theory of gravitation is the law by which all atoms of matter are attracted one to another with a force directly proportional to the product of the two masses, and inversely as the square of their distances. The power of gravitation was noticed and speculated upon by the Greeks, and Seneca noticed the attractive power of the moon over the ocean. Kepler investigated the subject of gravitation in 1615. Galileo {c. 1633) demonstrated the theory of gravitation. A system of gravitation was also projected by Hooke at the latter part of the seventeenth century. To Newton, however, is ascribed the honor of proving mathematically the truth of the theory in his great work the "Principia," published 1687. Newton's laws have since been carried out to great perfection in their application to complicated problems of astronomical and physical science.

Telepathy is a word coined about 1886 from the Greek to express the supposed power of communication between one mind and another by means unknown to the ordinary sense-organs. Some members of the Psychical Research Society believe that they have established the fact that such a power does exist in the material universe, and have attempted to turn the assumption to account in the explanation of certain unexplained natural phenomena.

The blowpipe is a small instrument used in the arts for glass-blowing and soldering metals, and in analytical chemistry and mineralogy for determining the nature of substances by the action of an intense and continuous heat. Its utility depends on the fact, that when a jet of air or oxygen is thrown into a flame, the rapidity of combustion is increased, while the effects are concentrated by diminishing the extent or space originally occupied by the flame.