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Macculloch, John A. - CELTIC MYTHOLOGY., pp. 125-126: The cave of "Cruachan" - also known as "Ireland's gate to Hell"; a legendary and ancient cave from which - according to legend - strange creatures would emerge in ancient times, causing havoc on the surface.
Macklin, John - STRANGE DESTINIES., Ace Books., NY.: The story of the "green-skinned children" who emerged from a cavern, speaking an unknown language. (Also see: Drake, W.B.)
McClellan, Alec - THE LOST WORLD OF AGHARTI., Souvenir Press., 1982: The link between the Nazi-backed 'Thule Society' and subterranean legends, and the 'Hollow Earth' theory. The author's own experience while caving in Yorkshire is also mentioned, along with various reports of subterranean civilizations as developed in legend, occultism, and science fiction.
Malakhov, A. - THE MYSTERY OF THE EARTH'S MANTLE (Translated from Russian by David Sobolev): Explores the mysteries of the earth's mantle and reports on Russian scientist's attempts to drill a shaft through the 'Mohorovicic Discontinuity' (or 'MOHO' - the division line separating the earth's crust from the mantle). Reports on their findings which startles the scientific world - PROOF that there is NO magma pockets beneath the outer CRUST layer of the earth (Also see: Malakhov, A.; NEW YORK TIMES; McWhirter, Norris).
Mamak, Zbigniew - IS THE EARTH HOLLOW? A two-part article in FATE magazine, July & Aug. 1980: Refers to several Hollow Earth theorists and their works, including an analysis of Willis George Emerson's book,  THE SMOKY GOD.
Mansfield, Abraham - THE GOLDEN GODDESS OF THE LEMURIANS., The Lemurian Foundation - Mt. Shasta; Redding, CA., 1970., Chapt. 1: A man is led into the bowels of Mt. Shasta in northern California and into an underground 'Lemurian' city and subterranean gardens producing gigantic vegetables, a mile or more under the surface of the mountain.
MANY CAVE DWELLINGS IN CHINA., Article in THE MILWAUKEE JOURNAL., Feb. 18, 1983: Refers to 40 million Chinese citizens who are said to live in underground cavern dwellings or subterranean levels beneath major cities, according to PEOPLE'S DAILY, a Chinese newspaper.
Marcella, Elena M. - THE QUEST FOR EDEN., Philosophical  Library, Inc., 1966., 270 pp.: The Persian tradition  of two underground cities - ‘Jaqobsa’ and ‘Jabulsa’ - the inhabitants of which will emerge, according to tradition, on "Judgement Day".
Marcoux, Charles A.
   --- DID SHAVER REALLY VISIT THE UNDERWORLD? Article in SHAVERTRON magazine., No. 14: The author describes 'astral' visits to subterranean cities and temples as a small child. 
   --- THE HIDDEN CITY OF CHIHUATLAN., Article in THE NEW ATLANTEAN JOURNAL (see: O'Connell)., Fall 1981: A sealed cave in a certain canyon near old Sonora, Mexico, which is said to lead to the ancient Aztec underworld or the hidden city of "Chihuatlan". (Also see: Brinton, D., & Folsom, F.)
   --- THE HIDDEN CITY OF CHIHUATLAN (booklet)., Published by the author., 1981. (Also see: Forman, Harrison)
   --- Letter in THE  HOLLOW HASSLE newsletter., Vol. 3, No. 1: Entrances to the subterranean world in the Organ mountains near Las Cruces, NM; in the Franklin mountains near El Paso, TX; and an underground cave with large stone steps leading deep into the unexplored depths of the earth, located near "El Moro" National Monument, northeast of Pie Town, NM.
   --- I SEARCH FOR THE PORTALS., Privately published by the author., Phoenix, AZ., 1981: The authors' own researches into cave entrances and inter-dimensional portals in and around the Superstition mountains of Arizona.
   --- MARKED BLADE., Two issued published: No. 1, Aug. 1956; No. 2, N.D.: Discusses the 'Shaver Mystery' and underground civilizations.
   --- NOTES OF CAVERNS., Article in THE HOLLOW HASSLE newsletter., Vol. 3, No. 3 - May 1982: Unusual reports of caves and tunnels throughout the world.
   --- TEROS IN THE 20TH CENTURY., Article in SHAVERTRON., No. 13: The author's encounter with two subterranean beings, dressed in surface attire, on a street corner in Flint, MI., in 1945.
Marcoux, Charles A. & Wight, George D. (See: Wight, George D.)
Margre, Maurice - THE RETURN OF THE MAGI., Philip Allan & Co., London., 1931., pp. 91-93: The legend of the cavern of ‘Ornolhac’, and its inhabitants.
Martin, Harold - EARTH SHAPED LIKE A DOUGHNUT., Article reprinted from an Atlanta, GA., newspaper, and appearing in the HOLLOW HASSLE newsletter, Vol.  1, No. 10: Refers to the Hollow Earth and the book 'THE SMOKY GOD', by Willis George Emerson.
Martin, Mary (Maiden name, formerly Mary LeVesque). Later remarried and became 'Mary Davis'.
Martin, Mary (LeVesque), Ed. - THE HOLLOW HASSLE., Quarterly newsletter., Colorado Springs, CO., Published 1972-1974., continued in 1981 before once again going out-of-print: Contained news, theories, and other information concerning the 'Hollow Earth' research field.  Matchett, Frank D. - Letter in AMAZING STORIES magazine., Feb. 1948., pp 165-166: Description of a tunnel entrance in Nevada.
Mather, Cotton (1663-1728) - Articles in  THE CHRISTIAN PHILOSOPHER. Mather, a Colonial Christian preacher, was one of the earliest proponents of the  'Hollow Earth' theory, supporting the idea of a Geo-concavitic sphere by combining theological thought with scientific theory. Mather was well known for the part he played in supporting the conviction of devil cultists in the Salem, MA., witch trials.
Maxwell, Robert - LEMURIA: FACT OR FICTION? The author claimed that he was taken into the inner cavern colony within Mt. Shasta, California, and was shown a large underground city by one of the 'Lemurians'. (Also see: Smith, Warren - THE HIDDEN SECRETS OF THE HOLLOW EARTH.,  pp. 33-37)
McBride, James
   --- CAPTAIN JOHN CLEVES SYMMES., From McBride's PIONEER BIOGRAPHIES., Vol. 2., Microfiche., PAMPHLETS IN AMERICAN HISTORY., No. B2174: Reports on Capt. Symmes' theories of a Hollow Earth with inhabited concentric spheres.
McCandless, Lyon - Letter in THE SHAVER MYSTERY MAGAZINE., Vol. 1, No, 1: The writer explores a strange artificial shaft in a cave near his home in Pittsburgh, PA., and hears some strange, “very deep”, sounds.
McDonald, Dr. George - Article in ASTRONAUTICS magazine., July 1962., p. 14-15: McDonald, a NASA scientist, stated that according to an analysis of the Moon’s motion, as well as other factors calculated into his lunar scientific model, the Moon appears to be hollow: “If the astronomical data are reduced, it is found that the data require that the interior of the Moon is more like a hollow than a homogeneous sphere.” The thesis that all moons and planets are hollow is not so difficult to comprehend, considering that all space bodies, while in the molten state of formation, spin-rotate rapidly, and like the inside of a washing machine in its’ “spin cycle”, the molten rock would naturally be removed outward from the center of the spin. Only that matter at the exact center which is not be subject to the spin-motion will remain, and this may explain why many planets are said to contain a small “sphere” of electromagnetic energy and molten “gas” which serves as a central heat and light source (a mini-sun if you will) which illuminates and heats the inner concavitic surface of these spheres. (Also see: Snyder, Al)
McGovern, Dr. William M. - JUNGLE TRAILS AND INCA RUINS., p. 438: References to caverns and tunnels in Peru, including the cavern of “Chincana” - the end of which has never been found and which is believed to communicate by way of a long passage with the “Temple of the Sun” in the heart of the city of Cuzco, Peru.
McKenna, James A. - BLACK RANGE TALES., 1969., Rio Grande Press., Gloricta, NM., 300 pp., illus.,: Chapter “Radium Wells” describes the discovery of an ancient cavern, within which were seen strange flashes of light, artifacts and remains of a prehistoric race of ancient Americans, and unusual magnetic activity. The cavern, located a few miles south of the New Mexican border, was not explored to its end due to its “bad air”.
McLaughlin, Marie L. - MYTHS AND LEGENDS OF THE SIOUX., 1916., Bismark Tribune Co., Bismark, ND., 200 pp., illus.,: Describes a smooth, polished shaft in the bottom of a cave within a mysterious butte, from which strange perfume-like odors emerge.
McWhirter, Norris - THE GUINNESS BOOK OF WORLD RECORDS., 1981., pp. 280-282: Man’s deepest known penetration (as of 1981) into the earth, including a drilling project began in May, 1976 at Saatly, Azerbaijan, U.S.S.R. (now Russia) in an attempt to reach the “Mohorovicic discontinuity” (or nick-named “MOHO”, the separating point bet0een the earth’s crust and the mantle), a target depth of 49,212 ft. (Also see: Article in the NEW YORK TIMES., Sept. 19. 1981., p. 3; & Malakhov, A.)
Mercer, Henry C. - THE HILL-CAVES OF YUCATAN., 1896., Lippincott Co.
Merrystone, Cyril - 1982: THE YEAR OF THE WARNING., Published by the Author., Bronx, NY., 1982., Distributed by ‘Gray Barker Books’, 2 Vols.: The location of ‘Hell’ inside the earth, the ingress and egress to which is gained by UFOs via the oceans. Argues that many UFO occupants are part of a ‘demonic’ race.
Merton, Loner Nikolai - BEYOND ARZARETH: A STORY OF THE LOST TEN TRIBES., Article in THE RELIEF SOCIETY MAGAZINE., Oct. 1919 - July 1920., Salt Lake City, Utah; Reprinted in SEARCH magazine., Palmer Publications., Summer 1980, Fall 1980, & Winter 1980-1981, under the title: “ARZARETH - LAND BEYOND THE POLE” (Forwarded by John Bringingham, who allegedly discovered this manuscript-diary telling of the experiences of the author, the sole survivor of a wrecked whaling vessel in the Arctic Ocean, and his encounter with the Lost Tribes of Israel, who reside in a hidden Polar country in the extreme north.
Messerschmidt, Gottfried - THE MESSERSCHMIDT MANUSCRIPT: A collection of various accounts about the Inner Earth, by a German  researcher. Parts were printed in THE HOLLOW EARTH BULLETIN., May 1967. One of the accounts in the edited version appears in 'THE HOLLOW EARTH', by Warren Smith: The account of a young French woman's frightening encounters with subterranean dwellers, and with the 'Gray Men' - a race of scientists from a distant star system, in tunnels under Paris, France.
Mezta, Frank J. - Letter in HIDDEN WORLD magazine, Winter 1962., pp. 1361-1363: Refers to a strange network of tunnels in Mexico, also an "enchanted cave" into which many people have disappeared, and an exploring party's encounter with two strange beings, one a half-man half-bull (similar to the "Le Mont Torreas" of Aztec legend, or the legend of the Minitor), and a "naked midget or little boy", deep inside the cave.
Michell, John, & Robert Richard - PHENOMENA: A BOOK OF WONDERS., Panther Books.,New York, NY., 1978: Contains a section on the Hollow Earth theory, and a photograph reputedly showing the polar opening.
MILE OF LIGHTS - Article in  SEARCH magazine., Fall 1980., p. 7: The discovery of "long rows of lighted candles as far as the eye could see," the origin and use of which remained a mystery, within an abandoned mine in Brewster, NY.
Miller, William M. - THE THEORY OF CONCENTRIC SPHERES., Article in ISIS magazine., Dec. 1941., pp. 507-514: The theory of concentric inner spheres, postulated by Captain John Cleves Symmes and others.
Millet, Clair (or 'Day-Ga-Chee') - THE LEGEND OF THE TAURTUMS: OF THE VALLEY OF THE SUN., a two-part article in THE NEW ATLANTEAN JOURNAL., Spring-Summer, 1981: An ancient race of 'little people' or 'Tuar-Tums' - who  live in subterranean cities under the 'Valley of the Sun' (Salt River Valley) of Arizona.
Mitchel, Alexander - A TREATISE ON NATURAL PHILOSOPHY., 1826. Information relating to the inner earth.
Mohr, Victor - A SPIRITUAL VISION OF THE UNIVERSE. Inner earth related information.
Mohr & Paulson - THE LIFE OF THE CAVE., 1968: Evidence of extended animal migrations underground in the central-eastern U.S., indicated by troglodytes found in widely separated caves, indicating past interconnections which have become blocked. These caverns are found from time to time during deep drilling operations.
Mohr, Professor (?) - A thesis on Thermometric investigations, title unknown: Marshall B. Gardner refers to Prof. Mohr of Bonn who "has written a very important paper on thermometric investigations of a 4,000 feet boring at Speremberg, and who finds that while there is an increase of temperature, as we go down, the rate of the increase gets less and less all the time, so that it will be nil; that is to say, there will no longer be any increase, and the point at which heat  would cease to increase would be about 13,550 feet." (Also see: Gardner, Marshal B. - A JOURNEY TO THE EARTH'S INTERIOR., p. 357)
Montesinos - MEMORIAS ANTIGUAS (HISTORALES, POLITACAS DEL PERU)., Publishing information not available: Refers to a gigantic subterranean 'road' stretching from Cuzco to Tiahuanaco, Peru, the origin of which remains unknown even to the Incas.
Montgomery, Ruth
   --- HERE AND HEREAFTER., pp. 75-77 & 157-160: Vast tunnels stretching beneath the Egyptian desert, an ancient underground civilization beneath the Arctic circle which existed long ago, and subterranean vaults under Inca ruins in Peru, containing priceless treasures.
   --- THE WORLD BEFORE., Fawcett Publications, Greenwich, CT., Chapt 4: A race of ancient 'Lemurians' who went underground to live in order to escape the saurians which roamed the earth, attacking humans, in ancient times.
MONTREAL: THE CITY THAT WENT UNDERGROUND - Article in THE LOS ANGELES TIMES., Aug. 10, 1972; Reprinted in OUTER SPACE PEOPLE AND INNER EARTH PEOPLE, by William L. Blessing: A climate controlled subterranean city consisting of miles of tunnels, plazas, concourses, etc., built under the surface of Montreal, Canada.
Mooney, Richard E. - GODS OF AIR AND DARKNESS., Stein & Day Publishers, NY., 1975: Refers to the island of Temuen (Nann Madol), on Ponape, in the Carolina Islands, where investigators reported the discovery of an ancient well, now filled with water. The well enters a tunnel, the beginning and end of which is unknown, and which has not - at the time of the report - been explored fully. (Also see: Von Daniken, Erich - THE GOLD OF THE GODS., Chapt. 4; & Rittlinger, Herbert - THE MEASURELESS OCEAN)
Moore, Justin H. - THE WORLD BEYOND: The belief of the Mewen Indians that their ancestors emerged from caves at "Kpp-lo-te" near where they lived until they were moved to reservations in California.
Moore,  Patrick - CAN YOU SPEAK VENUSIAN?  David & Charles Publishers, England., 1972: Contains a chapter in reference to the 'Hollow Earth'.
MORE MYSTERIES - Article in FATE magazine, June 1961, pp. 6-7: Statements  attributed to Dr. Gordon J. F. MacDonald of NASA that "studies of satellite orbits indicate that there are some huge unknown lumps inside the earth at depths of a thousand miles or more. At present we don't know where these lumps are; or what they consist of."
Moseley, James W. (See: Cohen, Richard)
MOUNTAIN CAVE HAS MYSTERY, MAYBE MONSTER - Article in the HOUSTON POST, Feb. 19, 1976; Reprinted in THE HOLLOW HASSLE newsletter, Aug. 198: The discovery by scientists of a cave, "the oldest in the world ... with smoothly vaulted roots and level floors..." located inside Mt. Autana in the Orinoco jungle, 400 miles south of Caracas, Venezuela, and believed to be the legendary home of a giant humanoid being.
MOUNT SHASTA HOLDS AURA OF MYSTERY - Article in the ALBUQUERQUE JOURNAL, New Mexico, 1981: Numerous mysteries surrounding this mountain in northern California, including the belief that it is the home of an ancient race of 'Lemurian' survivors.
Murdock, Mildred
   --- THE EAST'S "KING OF THE WORLD" - Article in FATE magazine, May, 1949,pp. 73-74: Mongolian and Tibetan legends of a subterranean land called 'Agharta' as it appears in Ossendowski's writings. (Also see: Ossendowski, Ferdinand - BEASTS, MEN & GODS)
   --- KING OF THE WORLD - Article in SEARCH magazine, July 1957, pp. 46-47: Information based on the research of Ferdinand Ossendowski concerning the legends of the subterranean 'world' of 'Agharta' or 'Agharti'.
MYSTERIOUS PATH TO THE UNKNOWN WORLD, THE - Author unknown, but reportedly published in Egypt: Describes a "third tunnel" near the Great Pyramid at Gizeh, said to lead deep into the earth.
MYSTERY OF THE LITTLE GREEN CHILDREN - Article in WEEKEND (British), July 22, 1970: The account of two "green-skinned children" who emerged from a cavern near Banjos, Spain, in August of 1887. (Also see: Drake, W. Raymond; & Wilkins, Harold T.)
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Nebel, Long John - THE WAY OUT WORLD., Prentice-Hall., Englewood Cliffs, NJ., 1961: Chapt. 9, pp. 134-140 - "Deros, Devils and Snowmen". A review of the 'Shaver Mystery', including MANTONG, the so-called Shaver alphabet.
Neihardt, John G. - BLACK  ELK  SPEAKS: Refers to a journey to the land of the thunder beings: "...You shall see and have from them my power; and they shall take you to the high and lonely 'center of the earth' that you may see even to the place where the sun continually shines, they shall take you there to understand ... for yours shall be the power of the white giant's wing, the cleansing wing..."
Nelson, Nicholas R. - PARADOX: Dorrance & Co., Cricket Terrace Center, Ardmore, PA: Refers to the Hollow earth and proposes a  point of view rarely explored in literature.
NEW ATLANTEAN JOURNAL, THE - Also see: O'Connell, Joan & Patrick. Article in the Summer, 1980 issue, p. 48: A Mexican, Jose Carmen Garcia, who claimed to have met a man who was taken into a subterranean city inhabited by tall, fair-skinned extraterrestrials beneath an extinct volcano near Irapuato, Mexico, where he was given a formula for growing gigantic vegetables. The man gave the formula to Garcia, who in turn presented it to the Rosicrucian Order in California.
Newell, Neil K. - SEARCH  FOR UTAH'S PRICELESS GOLD HOARD: Article in TREASURE magazine (date uncertain): John H. Koyle's "Dream Mine" which was founded upon his vision of a vast field of gold ore within seven ancient artificial caverns filled with ancient treasures, artifacts, and records from a prehistoric civilization near Spanish Fork, Utah. According to the vision this mine will, at a time of global economic collapse, begin  producing and shortly afterward excavators will break into the seven caverns, and it will eventually become the largest producing gold mine in the world. (Also see: Walton, Bruce - THE DREAM MINE STORY)
NEW WORLDS: See Boyes, Ivan
NEW YORK TIMES, THE - Article in the Sept. 29, 1981 issue, p. 3: Reports on a Russian drilling project at the Kola Peninsula and at Saatly in Azerbaijan, resulting in two unexpected findings. These included the discovery of traces of biological activity of fossil microorganisms at a depth of 22,000 ft., and a dramatic sudden increase of temperature at 33.000 ft., instead of a dropping of temperature as was expected. (See also: McWhirter, Norris &  Malakhov, A.)
Neiman, Lester F. - STRANGE DESERT ICE CAVE., Article in FATE magazine., June, 1972: The "Arnold Ice Cave" 27 miles northwest of Bend, Oregon., in the  Lava River State Park, which had never been fully explored and which contains a continuous river if ice leading into the earth, the cause and origin of which remain unexplained, this being especially puzzling since the cave lies in the middle of a desert.
Norman, Eric (Warren Smith, pseud.)
   --- HIDDEN SECRETS OF THE HOLLOW EARTH, THE., Zebra Books., New York, NY., 1976: Contains several reports of strange tunnels, and subterranean legends.
   --- INTO THE STRANGE., Popular Library., New York, NY., 1968, pp. 70-71: The Legend of 'Buck Hill Caverns' three miles north of Natural Bridge National Monument in Virginia, which is said to have a 'bottomless pit' from which strange human-like voices or cries are occasionally heard.
   --- SECRET FORCES OF THE PYRAMIDS., Zebra Books, New York, NY., 1975: Quotes R.C. (Doc) Anderson, noted explorer & 'psychic' (now deceased), on the Inner Earth mysteries.
   --- THIS HOLLOW EARTH., Lancer Books., New York, NY., 1972., Several accounts of encounters with subterranean dwellers, theories on the nature of the 'hollow' interior of the earth, and legends and traditions the world over of subterranean lands beneath the surface.
   --- UNDER PEOPLE, THE (The Startling Discovery of a Lost World)., Award Books., New York, NY., 1972: Unusual stories and claims about the bizarre inhabitants of the interior of the earth.
NORWOOD REVIEW OF ENGLAND - May 12, 1884: Summarizes the surprising discovery of a 'warm country' in the extreme north, by arctic explorers: "We do not admit that there is ice up to the pole - once inside the great ice barrier, a new world breaks upon the explorer, the climate is mild like that of England, and afterward, balmy as the Greek Isles."
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Obruchev, V.A. - PLUTONIA., Moscow, 1224: The romantic account of a voyage into the hollow interior of the earth. Although obviously fiction, the untranslated (at the time) work borrows heavily from 'Hollow Earth' pioneers, along with the writings of Jules Verne and H.G. Wells.
O'Connell, Joan (Editor) & Patrick O'Connell (President) - THE NEW ATLANTEAN JOURNAL., quarterly: Several back issued include articles on the Shaver Mystery, the Hollow Earth, and subterranean cities.
O'Connell, Patrick
   --- LOST CITIES AND ANCIENT SUBTERRANEAN PASSAGES., Article in THE NEW ATLANTEAN JOURNAL., Winter, 1980: Maps designating tunnel and mysterious cavern systems throughout the world.
   --- SACRED CAVES AND LOST CITIES OF THE ANCIENTS., Two-part article in the NEW ATLANTEAN JOURNAL., Summer - Fall, 1981: Tunnels and Lost Cities of Central America, and Strange mines, caverns, tunnels and underground cities built long ago by the ancients.
Oga-Make - TRIBAL MEMORIES OF THE FLYING SAUCERS: Article in FATE magazine., Sept. 1949: Written by a Navaho 'Indian' (native American) who tells of a Paiute tribal legend of a race of beings, the Hav-Mu-Suvs, who  live/lived in a subterranean paradise -- huge caverns containing electromagnetically-induced phosphorescent atmospheric auroral-like illumination -- deep underneath the Panamint Mountains adjacent to Death Valley, California. (Also see: Lee, Bourke - DEATH VALLEY MEN) 
Old Dog Tray (reputedly the pseudonym for Gray Barker) - MIB/HOLLOW EARTH ALERT: A letter circulated to Inner Earth researchers and reprinted in GRAY BARKER'S NEWSLETTER., Gray Barker Books., Dec. 1982., No, 17: Warns of visits by strange representatives promising an expedition to the Hollow Earth. These visitors turn up unexpectedly, driving a car filled with electronic equipment, and according to some may be 'programmed' androids. In a following commentary Barker reprints letters from others visited by these 'representatives', one of whom was put into a hypnotic state by the 'gaze' of one of the 'men'.
Oliver, Frederick Spencer (amanuenais) - See: Phylos, the Thibetan
Osbourne, Harold - SOUTH AMERICAN MYTHOLOGY., p. 119: The belief of the Tupari Indians, who live up the Rio Bronco (or Parima) river in the Mato Grosso region of Brazil, that their forefathers emerged long ago from an underground land, and that many of their ancestors remained inside the earth. These "Kinno" - according to tradition - will one day migrate to the surface of the earth as the Tupari ancestors did long ago, when many of those on the surface have died (of war, disease, cataclysm, etc.); p. 42 also tells of the place of emergence of the ancestors of the Inca Nation, three caves collectively called "Paccari-Tambo" which are believed to be located about 20 miles east of the city of Cuzco, Peru.
Ossendowski, Ferdinand - BEASTS, MEN AND GODS., E.P. Dutton & Co., New York, NY., 1922: Chinese and Mongolian beliefs and stories about the 'Agharti', a race of highly advanced humans who live in a vast subterranean cavern world stretching beneath a large part of Asia, a kingdom ruled and led by a line of long-lived leaders known as 'The King of the World'. (Also see: Roerich, Nicholas)