Occasionally, however, we see a little around one or the other edge. This phenomenon is known as libration in longitude. Phases. The moon's changes in shape from a crescent to a full disc are due conjointly to the globular form of the moon, its motion and the fact that it does not shine by its native light, but simply reflects the solar rays. The illuminated (or convex) edge of its figure is always turned toward the sun. When right opposite the sun it appears as full, and sometimes is so situated as to be partially obscured by the earth's shadow. When it is near the sun in the sky it appears as a thin crescent, turning almost entirely its dark side to the earth. Sometimes, at new moon, it comes between us and the sun, obscuring his disc either in a partial or total eclipse. At either half moon the moon is said to be in its quadrature, or in the "first" or "last quarter." At new and full moon it is said to be in syzygy (Greek syn, "together"; zygon, "yoke"). These changes result from the constant darkness of one side of the moon, and constant brightness of the other, the crescent being larger or smaller as, from the moon's change of position, more or less of the bright side is seen from the earth. Eclipses.- Whenever the earth gets between the moon and the sun, cutting off the light of the latter, a so-called eclipse of the moon takes place. An eclipse of the moon occurs only at full moon. During a lunar cycle there will be, on the average, twenty-nine eclipses of the moon. The Harvest Moon. - If the plane of the moon's orbit coincided with that of the earth's equator, the moon would rise about fifty minutes later each day, but owing to the inclination between these planes to one another this retardation is quite different at different times. This retardation may be reduced to nothing when in the northern latitude full moon occurs near the autumnal equinox, so that for several nights the full moon rises about the same time soon after sunset. At or about the time of harvest in the northern temperate zone the sun in its annual course is approaching the celestial equator, which it crosses from north to south on September 22. On that date it sets close to the exact western point of the horizon. If it happens to be also full moon, the moon rises that evening as the sun sets, or close to the exact eastern point of the horizon. Thus it begins to give light at sunset, and continues to do so until sunrise, when it sets opposite the sun, just as the latter rises. This arrangement holds good without any great change for several days, so that there is practically no darkness, especially if the weather is fine. The full moon which thus illumines the autumn night is called the harvest moon. The hunter's moon is the next full moon after the harvest moon; the same phenomenon, less marked, occurs. Tides. The chief cause of the tides is the attraction of the moon, which, affecting most strongly the side of the earth nearest to it, draws or heaps up the waters in the parts of the earth successively turned toward it. At the same time the moon attracts the bulk of the earth, and, as it were, pulls the earth away from the water on the surface furthest from it, so that here also the water is raised, although not quite so much as on the nearer side. The waters being thus heaped up at the same time in these two parts of the earth, and the waters situated half way between them being thus necessarily depressed, two high and low tides occur in the period of a little more than one revolution of the earth on its axis. When the sun and moon are in conjunction or opposition, at times of new and full moon, their tidal waves will be superposed crest upon crest, and the effect will be what is called "spring tide"; when they are in quadrature the lunar tide will be partially neutralized by the solar tide, and the result will be a "neap tide.' Size, Volume, Mass, Density. The moon's diameter is 2,163 miles, a little more than a quarter of the earth's. Its surface is therefore 0.074 of the earth's, or, in square miles, about 14,657,402. The earth taken as a unit, the moon's density is 0.63; mass, 1/80, volume 1/50 that is to say, it would require the materials of 80 moons to form our globe; the earth is 50 times larger than the moon and its density is in the ratio of 10 to 16. Its smaller size and mass cause gravity to be only 1⁄4 of the terrestrial attraction; the same exertion which would lift a given weight here would raise a weight six times as great there, and a body instead of falling 16 feet in the first second would fall only 2% feet. Light, Temperature. Like the earth, the moon has no light of its own, but receives all from the sun, and its day-the interval from sunrise to sunrise is a month. At full moon it sends to us about 1-600,000 part of the light given by the midday sun. Physical Conditions, as Seen Through the Telescope. The surface of the moon is totally unlike that of our earth. All the details are hard, cold and glaring in their delineations. All are marked in white and black or in various shades of yellowish gray. Nothing like mist, cloud or water has ever been seen. The so-called seas on the moon are simply portions of the surface darker in color than the average and very much broken up by craters and mountain ranges. Nor is there any evidence of an atmosphere. Observation of the stars suddenly occulted by the moon, as well as the spectroscope, confirms this, and if there be even an attenuated atmosphere it cannot have more than 1/200 of the surface density of our own. In consequence there is no vegetation, no life. The mountain ranges, called the lunar Alps, Appenines, Cordilleras, etc., range from 20,000 feet in height downward; the lunar rills, clefts or cracks in the surface pass often right through mountains and valleys, sometimes for a distance of 300 miles, their breadth being relatively so small as to give them the appearance of true cracks. The whole aspect suggests volcanic action on the lunar surface in remote ages, but nothing like an active volcano has ever been seen. FACTS ABOUT THE EARTH. The total area of the earth is about 197,000,000 square miles, and its total population 1,626,000,000. The area of the water of the earth is about 145,000,000 square miles. The area of the land of the earth is about 52,000,000 square miles. The figures of population, excepting those for the United States, are taken from the Year Book of the Bureau des Longitudes. Including all islands in the Eastern Indian and Southern Pacific oceans. Including population in the Dutch East Indies. The largest states, comprising parent country and colonies or possessions, are: According to the number of inhabitants, the countries range as follows: British Empire and Colonies....403,000,000 | Austria-Hungary 50,000,000 China Russian Empire. United States.. France 350,000,000 Netherlands 44,000,000 .152,000,000 Turkey 38,000,000 98,000,000 [Italy 36,000,000 81,000,000 Belgium and the Congo. 27,000,000 German Empire... Japan and Corea.. 1. The largest cities in the world are: London 2. New York 3. Paris 78,000,000 Spain 20,000,000 62,000,000| .2,186,079 9. Philadelphia 1,549,008 2,185,283 10. Moscow 1,359,254 Height. 20,464 feet 23.080 feet 18,526 feet 29,002 feet 20,065 feet 32.768 feet 7,167 feet Mt. McKinley, Alaska... Aconcagua, Chili.... Elbrooz, Caucasus, Russia... Mt. Everest, Himalaya, India. Kilimandjaro, East Africa... Mt. Hercules, North New Guinea Kosciusko The longest rivers in the world are: In Europe, Volga, about 2,200 miles; in Asia, Yenisei, about 2,700-3,000 miles, and Yang-tse-Kiang, about 3,000; in Africa, Nile. about 3,240 miles; in North America, Mississippi and Missouri, 4,300 miles; in South America, Amazon and Beni, 4,000 miles; in Australia, Darling, more than 2,345 miles. The largest lake in the world is Lake Superior. It covers an area of 31,200 square miles and has a mean depth of about 475 feet. The greatest cataract in the world, surpassing by far Niagara and Zambezi Falls, on the Ignazu River, which partly separates Brazil from Argentina, one thousand miles by boat from the nearest settlement. The precipice over which the river plunges is 210 feet high, that of Niagara being 167 feet. The cataract is 13,123 feet wide, or about two and a half times as wide as Niagara. It is estimated that 100,000,000 tons of water passes over Niagara in an hour; a like estimate gives the Falls of Ignazu 140,000,000 tons. The oldest city in the world is Damascus, in Syria. The exact date of the founding of this city, once so famous for its manufacture of silks, jewelry and blades, is not known, but it is said to have been begun by a greatgrandson of Noah, and probably is 4,200 years old. Next comes Athens, the capital of Greece, which is about 3,453 years old older than any other European city. Peking, the capital of China, is said to be about 3,000 years old. Jerusalem, which was a Jebusite city in the days of Abraham, is 3,000 years old at least. The coldest country in the world is Werchojansk, in Siberia, longitude 133 degrees 51 minutes east, latitude 67 degrees 34 minutes north, where a lowest temperature of minus 90 degrees Fahrenheit has been observed, and the mean of January is minus 48 degrees Fahrenheit. The country is inhabited by about one hundred and five thousand persons of the Jakut and Lamat races. GEOLOGICAL STRATA AND ERAS. The history of the earth is divided into five eras with corresponding rock systems: 1. Archaean or Eozoic (dawn of life), embodied in the Laurentian system; 2, Palaeozoic (old life), embodied in the Palaeozoic or primary system; 3. Mesozoic (middle life), recorded in the secondary system; 4. Cenozoic (present life), recorded in the Tertiary and Quaternary systems, and 5, the Psychozoic (Era of the Mind), recorded in the recent system. These grand divisions, with the exception of the last, are founded on an almost universal unconformity of the soil. The history of the earth is otherwise divided into Seven Ages, founded on the culmination of certain great classes of organisms. These are: 5. 1. The Archaean or Eozoic Age, represented by the Laurentian system of rocks. 2. The Age of Mollusks, represented by the Silurian series of rocks. 3. The Age of Fishes, represented by the Devonian rocks. 4. The Age of Acrogens, or sometimes called the Amphibian, represented by the Carboniferous rocks. The Age of Reptiles, represented by the secondary rocks. 6. The Age of Mammals, by the Tertiary and Quatenary, and 7. The Age of Man, by the recent rocks. The diagram shows how the ages correspond with the eras: [The vertical height represents time, the strong horizontal lines separate the ages, the shaded spaces represent the origin of the dominant classes of animals and plants. Thus, for instance, the class of reptiles commenced in the time of Carboniferous rocks.] The subdivisions of eras and ages into periods and epochs are founded on less nonconformity in the rock system, and less conspicuous changes in the life system. The names and periods are often, and of epochs are nearly always, local, and therefore different in different countries. The table represents, as far as periods, the classification used in America. The total thickness of all the strata known amounts to 72,000 metres (44.74 miles), of which about 1,000 metres belong to the Cenozoic (recent life) era, 3,000 to the Mesozoic (middle life), 30,000 to the Palaeozoic (old life), and 38,000 to the Eozoic (dawn of life) eras. From these figures the approximate relative duration of the eras is calculated. THE AGE OF THE EARTH, In a publication issued in July, 1910, by the Smithsonian Institution, the age of the earth was estimated by Frank Wigglesworth Clarke and George F. Becker, of the Geological Survey, as "not above seventy million or below fifty-five million years." The age of the earth always has been a subject for discussion among men of science, and largely without any definite agreement among the representatives of the different branches of studies on account of the different points of approach. The more recent discussions as to the earth's age have placed the time as follows: Lord Kelvin, in 1862, 20,000,000 to 400,000,000 years, with a probable 98,000,000 years; in 1897 Lord Kelvin revised his figures to 20,000,000 to 40,000,000 years; Clarence King and Carl Varus, in 1893, 24,000,000 years: De Lapparent, in 1890, 67,000,000 to 90,000,000 years; Charles D. Walcott, secretary of the Smithsonian Institution, in 1893, maximum age, 70,000,000 years; J. Joly, in 1899, age of the ocean, 80,000,000 to 90,000,000 years, and W. J. Sollas, in 1909, age of the ocean, 80,000,000 to 150,000,000 years. THE RACES OF MANKIND. While from the researches of the physiologist, the anatomist, the philologist and the psychologist the same testimony is obtained as to the specific unity of the human race, ethnology for convenient classification divides men, according to their physical or psychical characteristics, into groups, families, clans, tribes, and, on account of their distribution, these are sometimes named for geographical divisions. In these efforts of classification different schemes have been tried. Linnæus classifies the races according to geographical areas. Dall divides men Into three groups: white, black and yellow; Garland, into six races, separating the Dravidians from the other groups. The cranological school founded by the elder Retzius made the shape of the head the basis of classification, and accordingly mankind was divided into long skulled and short, broad skulled races. Blumenthal gives five groups, classified according to the color of the skin. Professor Huxley also designated five groups along somewhat similar lines. Morton used the skull as a basis of classification; Haeckel and Broca the hair, and Hale language. The tendency now seems to be to return to the earlier classification and its three greater subdivisions white, black and yellow, or Caucasian, Negro and Mongolian, with the addition of two more subdivisions, red and brown, or American and Malay. Under such plan Blumenthal's scheme of dividing men according to the color of the skin can be used. Under it there are grouped: (1) Caucasian, or white; (2) Ethiopian, or black; (3) Mongolian, or yellow; (4) American, or red; (5) Malay, or brown. Classified in this manner, the human species presents the subdivisions shown in the following table, as given by Professor Amos W. Butler: I. Negrillo II. Negro III. Negroid 3. Caucasic Groups of peoples. 1. Libyan 2. Egyptian 3. East African 1. Arabian 2. Abyssinian 13. Chaldean Euskarian Indo-Germanic or Certividic peoples Peoples of the Caucasus African or Negro Race. Traits-Color, black or dark. Hair, frizzly. Nose, broad. §1. Central African. Dwarfs of the Congo 2. South African... Bushmen, Hottentots I. Sinitic Traits Color, yellow or olive, Hair, straight. Nose, medium. II. Sibiric Traits-Color, coppery. I. Northern II. Central III. Southern 1. Arctic Oceanic Race. Traits-Color, dark. Hair, wavy or frizzly. Nose, medium or narrow. *"The Jewish Year Book," just published in London, estimates the number of Jews in the world at 11,625,656, viz., Europe, 8,892,019; Asia, 432,855; Africa, 379,750; America, 1,903,926; Australasia, 17,106. |