Earth's Surface, The.- The earth's surface covers an area of about 197,000,000 square miles, of which only about one fourth is land.

Dyeing is attributed to the Tyrians, about from an invention of B. T. Babbitt, patented 1500 B. C. The English are said to have in 1878. sent fine goods to be dyed in Holland till the art was brought to them, probably in 1608. A statute against abuses in dyeing passed in 1783. The art has been greatly improved by chemical research. Among the most prominent names connected with the art of dyeing is that of Dr. Stenhouse, who in 1848 invented a number of beautiful dyes,- mauve, magenta, red, green, black.

Dynamite. As generally manufactured, dynamite consists of infusorial earth, porcelain earth, coal-dust, siliceous ashes or the like, saturated with about three times its weight of nitro-glycerine, a compound which is produced by the action of a mixture of strong nitric and sulphuric acids on glycerine at low temperatures, though the proportions vary with different makers. According to its elements, it is to the eye a grayish-brown, reddish, or blackish powder, damp and greasy to the touch, and without smell. Its explosive power is about eight times greater than that of gunpowder. The manufacture of dynamite is attended with great danger, owing to the proneness of nitro-glycerine to explosion even at the slightest shock. The explosive force of the latter substance, which has the appearance of common oil, is about ten times greater than that of gunpowder.

Lowlands are tracts, either level or diversified by hill and vale, not elevated more than 1,000 feet above sea-level. Deserts are extensive tracts destitute of water, and, consequently, of vegetation and animal life.

Silvas are forest plains. Plains that produce grass, but not trees, are known in North America as prairies; in South America as llanos and pampas; in Asia and Southeastern Europe as steppes.

The desert of Sahara, as far as known, consists partly of table lands and partly of low plains. It is interspersed with oases, or fertile spots, which are generally lower than the surrounding country; some of these are of considerable extent and well populated.

A mountain is an elevation of land exceeding 2,000 feet in height. A hill is less than 2,000 feet in height.

A mountain chain is a long, elevated ridge, or several mountains extending in a line.

Mountains are of great use to man. They attract the clouds, condense their moisture, and store up in reservoirs the water received from them, sending it forth again in streams, from thousands of springs, to fertilize the soil. They increase the surface of the earth, giving variety to its vegetable productions. They protect the adjacent countries from cold and piercing winds, and thus exert a favorable influence on their climate.

An avalanche is a large mass of snow, ice, and earth, sliding or rolling down a mountain. A water shed is the mountain chain or ridge of land which separates one basin from another, and from which the rivers flow.

A mountain pass is an elevated road crossing a mountain chain through a natural opening

Dynamite Gun.-The nitro-gelatine or dynamite gun, known as the “Zalinski gun, was the invention of Lieutenant Zalinski and Captain Bartlett of the United States army. It is a long tube made of wrought iron, lined with seamless brass tubing one eighth of an inch thick. The projectile used is shaped like a huge rocket, five or six feet in length. The stick of the rocket has a wooden or metal base large enough to fill the bore of the gun, and against this base the pressure of the air (the propelling force being compressed air)-1,000 pounds to the square inch-is exerted. The head of the rocket contains from fifty to sixty or depression. pounds or more - of nitro-gelatine, a new explosive made of nitro-glycerine and guncotton. The projectile, being shot from the gun, is exploded, after reaching its mark, by electricity. A small battery is fixed in the head of each shot, and the discharge is effected by concussion if the shot strikes, or by action of water on a sensitized surface if the shot lights in the sea. It is thought that a submarine explosion within 100 feet of a ship will be disastrous in eight cases out of ten. The gun is from 40 to 75 feet in length, and of caliber from 6 to 10 inches. The mechanical arrangement for compressing the air in the gun and discharging the piece is said to be taken

Glaciers are immense masses of ice formed by the accumulated snows upon the mountain tops. They fill in vast valleys, and have an onward motion throughout like a liquid or semi-liquid body. Their course down the slopes is very slow, but, like rivers, they flow faster in the middle than at the bottom and sides. The lower extremities are constantly melting, forming torrents and mountain streams, while the upper parts are fed by the snows. Rocks of immense size are torn off and carried down by glaciers. They occur in the greatest numbers in the Alps. When a glacier reaches the ocean large fragments are broken off and float away as icebergs.

Electric Light, The, was first invented

Earthquakes.-The phenomena con- every earthquake can be traced to a focus nected with earthquakes have been variously within the earth, and that this lies directly bedescribed. Many writers refer to appearances neath the point of greatest disturbance on the in the heavens, or changes in the atmosphere, earth's surface. There are creditable records which to them seem to have some connection of. between 6,000 and 7,000 earthquakes, bewith the catastrophes they narrate. They tell tween 1606 B. C. and A. D. 1842. In the of irregularities in the seasons preceding or great Lisbon earthquake no less than 60,000 following the shock; of sudden gusts of wind, perished, while in that of Calabria, in the end interrupted by sudden calms; of violent rains of the last century, 40,000 were destroyed. It at unusual seasons or in countries where such is estimated that at least 13,000,000 of the phenomena are almost unknown; of a redden-human race have perished in this way. ing of the sun's disk; of a haziness in the air, often continued for months; and similar by Sir Humphry Davy, in the early part of phenomena. But these are so irregular in their this century, who produced the arc light with appearance, and have been so seldom observed a battery of 2,000 cells. It was not in pracassociated with more than a single earthquake, tical use, however, until 1844, when improvethat in the absence of any decided reason to ments in its manner of construction were the contrary there seems good ground for be- made by a Frenchman named Foucault, and lieving they have no real connection with the it was used to illuminate the Place de la Conearthquake. The general opinion of investi- cord, in Paris. In 1855, Jules Duboscq's gators is that these agitations proceed from electric lamp--thus far the most perfect of within outward, and are not of atmospheric or the kind was shown at the Paris Exposiother external origin. True, Professor Alexis tion; but, though improvements were made Perry, of Dijon, France, thought he discovered in the invention during the twenty years folrelations between the ages of the moon and lowing, little was accomplished toward practithese occurrences which seemed to sustain the cal electric lighting until the invention of theory of Zantedeschi that the liquid nucleus Jablochkoff's candle. Paul Jablochkoff was of the earth responds to the moon's attraction a Russian, who resigned his position under in tides, somewhat as the coast does; but the the government in 1875 to devote his time theory that the earth has a liquid nucleus cov- wholly to scientific study. It was his intenered with only a thin, solid crust is losing ad- tion to visit the Centennial Exposition in Amerherents continually. All theorists are agreed, ica, but he was induced to remain in Paris, as to the connection between volcanoes and where, in 1876, he produced the electric canearthquakes, that they are produced by the dle, whose discovery made a great sensation. same subterraneous agency. Mr. Mallet, in The light given by this candle was soft an elaborate report on the subject presented to and steady, and a great many of them speedily the British Association, proposed an ingenious came into use in Europe. In the last fifteen theory. He assumes that volcanoes and the years great progress has been made, and there centers of earthquake disturbances are near the are now many different styles and forms, but sea or other large supplies of water; and he in their essential features they nearly all come says that when an eruption of igneous matter under two general classes the arc light and takes place beneath the sea-bottom the first the incandescent light. The arc light is, in action must be to open up large fissures in its principle, the same as that invented by Davy, rocky material, or to lift and remove its inco- the improvements consisting in different deherent portions, such as sand, mud, gravel, vices for regulating and maintaining at a etc. The water, on meeting the heated sur- constant distance the tips, and in different face, assumes the spheroidal state. While in preparations for the substance of these tips, this condition the intestine motion may be which are generally of carbon. The light is great, but little steam is generated; but no produced as follows: Two tips connected with sooner have the surfaces cooled than the water the opposite poles of a strong battery are comes into close contact with them, and a vast brought near to each other. The electricity, volume of steam is evolved explosively and overcoming the resistance of the air, jumps blown off into the deep and cold water of the from one tip to the other, and in so doing gensea, where it is condensed, and thus a blow erates such an intense heat that the particles of the most tremendous sort is given at the on the end of the one tip are volatilized and volcanic focus, and, being transferred out- carried to the other in a condition of white heat, wardly in all directions, is transmitted as the forming an arc of light of intense brilliancy. earthquake shock. Whatever their origin, Thus one tip is slowly consumed and the other whether of one cause or various causes, the somewhat increased, and hence the necessity prevailing opinion still is that the vibrations of of regulators for the tips, whence these lights

are sometimes called regulated lamps. Brush patent is the arc light best known and most used in America. In lights of the incandescent class a lighter current is used, and the luminous substance is not consumed, being inclosed in a sealed glass bulb from which the air has been exhausted. It consists of a loop magnetic rotation. of a thin fiber of some infusible substance (car-imentists and theorists were busy searching bon has been found the best), inclosed in a for ways and means by which the electrical vacuum, as just stated. The ends of this fiber energy could be utilized as a mechanical power, are carried through the neck of the bulb and and to-day the galvanic battery and electric connected with the opposite poles of the bat- dynamo are rapidly ousting steam, and in a tery; then the current, in passing through thousand ways doing its work with less noise, such a small conductor, has to overcome a high expense, and better results. resistance, and in so doing generates a heat sufficient to maintain the entire loop at a steady temperature of white heat. The principal forms of the incandescent light are those of Edison, Swan, Maxim, and Siemens. It is perhaps worthy of note that the great impetus given to electric lighting by the work of Thomas Edison has been not so much in improving the lamp as in cheapening the process of generating the electricity and inventing a ready mode of dividing the light. Hitherto the two principal barriers in the way of applying the electric light to public use had been the expense attendant upon the production of the electric force and the difficulty of using it simultaneously at a large number of illuminating points.

The most important fact, viz. the magnetic action of the electrical current. This was in 1820. As soon as the discovery reached France, the eminent French philosopher Ampère set to work to develop the important consequences it involved. Faraday in 1820, discovered electricFrom this time up, exper

As to the question of the real nature of electricity, recent experiments and further knowledge of its properties rather open fresh avenues to new hypotheses than point to the truth of any one special theory. Some identify electricity with energy, some with matter, and some with the subtle all-pervading "ether." At all events it has been computed that in every single cubic foot of ether there are locked up 10,000 foot-tons of energy! The latest researches give well-founded hopes that this inconceivably vast storehouse of power will one day be accessible to man. And herein lies the splendid possibility of a new and mighty successor to the decreasing energy of our coal-fields, with the speedy extinction of which alarmists threaten us. By creating in a room a powerful electrostatic field alternating very rapidly, Professor Nicola Tesla brought it to such a state that illuminating appliances could be placed anywhere, and kept lighted without being electrically connected with anything! He suspended two sheets of metal, each connected with a terminal of the electric coil, between which an exhausted tube, carried anywhither, remained always lumi

Electricity. As far back as 321 B. C., the ancient philosopher Theophrastus mentions the power of amber to attract straws and dry leaves. Pliny, in 70 A. D., writes concerning the same phenomenon, and it is from the Greek name of "amber," pronounced "electron," that we call this phenomenon "electricity." Dr. Gilbert, of Colchester, may be considered the founder of the science of electricity, for it was he that carefully re-nous. peated the observations of the ancients, and experimented in various ways and published these experiments in a book during the period between 1540 and 1603. Sir William Watson (1715 to 1807) distinctly announced the theory of positive and negative electricity, which was afterwards elaborated by Dr. Benjamin Franklin. Dr. Franklin also established the fact that the lightning was an electrical spark, similar to that made by an electric machine or Leyden jar. In 1790, Galvani discovered that the contact of metals produced muscular contraction in the legs of a dead frog, and in 1800, Volta discovered the art of generating electricity by contact of metals with damp cloths. From these we obtained the galvanic battery and the voltaic pile.

It remained with Prof. H. C. Oersted, of Copenhagen, however, to bring forward the

A true flame can now therefore be produced without chemical aid — a flame yielding light and heat without the consumption of material or any chemical process! Further, these and similar experiments on electric radiation, which now advances so brilliantly to the forefront, by Tesla and Crookes, etc., point to the bewildering possibility of telegraphy without wires, without cables, without posts. There is considerable evidence to show that, could the electric ether-waves be obtained sufficiently short, the rays would fall within the limits of visibility, and thus place the final crown of proof on the magnificent experiments of Hertz and others, who would make light an electric phenomenon.

As regards the effect on the human body of alternating currents of very high frequency (which at best have a very doubtful reputation) it has been found that, as the rapidity of

the alternation increases, they become, not ent forms, but generally modeled on the inmore but less dangerous. In fact, Tatum has ventions of Plante and Faure. The efforts of shown that their fatal effects are nearly in-inventors have been mainly directed toward versely proportionate to their frequency. Thus, reducing the weight of the cells and to deviswith currents alternating about 5,000 per sec- ing new ways of holding red-lead on the plates. ond, the current needed to become fatal is This last-named substance, becoming porous, about ten times greater than at the ordinary drops off readily, and for this reason the inlow frequency of about 120 per second. With casements of flannel, etc., were first devised. still higher frequencies used by Tesla (up to In some of the storage-batteries a plate or 20,000 per second) the currents are incompar- frame of cast lead is used, with receptacles, ably less dangerous than at low frequencies; cells, etc., which are filled with the red-lead. but still altogether harmless.

The articles are then weighed and suspended times of a bluish color, and it is prepared for in the solution, and are left there until a suf- use by crushing the lumps in a stamp mill, ficient amount of silver has been deposited and then passing the powder through sieves of upon them. This amount is tested by weight. different degrees of fineness. For the most If the additional weight is not gained within delicate uses of opticians the powder is graded the expected time the article is put in the solu- by the process known to chemists as elutriation again. When finally taken out, the arti- tion. Emery was for a long time brought cles are rubbed with brushes of fine wire and from the island of Naxos in the Grecian Archcleaned with fine sand; they are then polished ipelago. The Greek government granted a on revolving brushes with rotten-stone, then monopoly of its trade to an English merchant. with chamois-leather and rouge. The process In 1847, Dr. J. Lawrence Smith, an American of electro-gilding is essentially the same, with explorer in the employ of the Turkish governthe exception that gold is substituted for ment, found deposits of the mineral at various silver. points in Asia Minor, and the monopoly was destroyed and the price lowered. Deposits of emery have since been found in Bohemia, in the Ural Mountains, in Australia, and in North Carolina, Georgia, and Montana. The supply from these deposits is too small, however, to compete with that which is brought from Turkey and Naxos.

Embalming. The ancient Egyptians believed that their souls, after many thousand years, would come to re-inhabit their bodies, in case these latter were preserved entire. Hence arose their practice of embalming the dead. The Egyptian manner of preserving the dead has been the admiration and wonder of modern times. They render the body not only incorruptible, but it retains its full proportion of size, symmetry of feature, and personal likeness. They called the embalmed bodies mummies, some of which, buried 3,000 years ago, are perfect to this day. The art of such embalming is now lost. When Nicodemus came with Joseph of Arimathea to pay the last duties to our Saviour after his crucifixion, he brought a mixture of myrrh and aloes to embalm his body. Carbolic acid was successfully employed by Professor Seely in America, in 1868. The modern method of embalming generally consists of an injection of camphorated spirits of wine into the arteries and veins, though many other chemical substances are successfully used.

Embroidery.-Its invention is generally ascribed to the Phrygians; but the Sidonians excelled in it, and it is mentioned by Homer and other ancient authors, in the year 1491 B. C. The latter were particularly skilled in decorative species of needlework. The first embroidery machine is said to have been invented by John Duncas, of Glasgow, in 1804. Heilman's embroidery machine was patented by Kochlin. An ancient existing specimen of beautiful embroidery is the Bayeux tapestry, worked by Matilda, the queen of William the First of England. It is nineteen inches wide, 214 feet long, and is divided into compartments showing the events from the visit of Harold to the Norman court to his death at Hastings. It was reproduced by autotype process, with notes, in 1875.

Emery is found, upon analysis, to be composed of alumina, oxide of iron, and silica, with a little lime. It is a dull, opaque substance, sometimes of a grayish black, some

Engraving. The engraving of gems is a branch of art of the highest antiquity. The earliest writers make mention of engraved seals and seal rings, and there still exist many antique engravings equal to later productions of similar artists. Engraving from plates and wood is chiefly of modern invention, having its origin about the middle of the fifteenth century. Engraving on glass was perfected to an art by Boudier of Paris, 1799. The art of engraving, especially in photographic processes, has made great progress in the United States during the past quarter century. Prints from engraved copper plates made their appearance about 1450, and were first produced in Germany. Masso is considered to have been the first Italian engraver, about 1440. Etchings on copper by means of aqua fortis is reputed to have been discovered by Francis Mazzuoli, about 1532. Etching was later practiced by Albert Durer, and most especially by Rembrandt. Its revival began about 1860. Mezzotints are said to have been discovered by Colonel Von Siegen, who engraved the portrait of Princess Amelia of Hesse in mezzotint, in 1643; it was improved by Prince Rupert in 1648; and by Sir Christopher Wren, about 1662. The mode of engraving on soft steel, which after it has been hardened will multiply copper plates and fine impressions, indefinitely, was introduced into England by Messrs. Perkins & Heath of Philadelphia, in 1819.

Entomology, the science of insects, is based upon the arrangements of Linnæus, A. D. 1739. The Entomological Society of London was instituted in 1833. A national entomological exhibition at the Westminster aquarium was opened March, 1878. Numerous chairs of entomology have been established in