[1.] “James Dwight Dana.” (1813-⸺.) An American geologist and mineralogist; the author of several works on these and other sciences. He went out as mineralogist and geologist appointed by the United States Government with the exploring expedition sent to the Southern and Pacific Oceans in 1838, and returned in 1842. For the next fourteen years he was busily engaged in preparing for publication the reports of this exploration. These were published by the government and formed valuable records. For many years he was one of the editors of the American Journal of Science and Arts. He has been elected to membership in several learned European societies and royal academies.
[2.] “Eisenlohr,” iˈzen-lore. (1799-1872.) A German physicist. He was a Heidelburg student, and in 1819 removed to Mannheim, where he became a teacher of mathematical and physical science in the lyceum. He was afterward a professor at Carlsruhe. A Manual of Physics is his chief work.
[3.] “Geissler’s tubes,” ghīceˈler. The spectrum of any gas can be best obtained by placing the gas in these tubes, and then passing the electric current through. If the gas is hydrogen, the spectrum will consist of a bright red, a green, and a blue line. Each gas casts its own spectrum. In this way the spectroscope aids in the analysis of substances. The different spectra formed reveal the elements.
[4.] “Sir John Herschel.” (1792-1871.) An English astronomer. His great enterprise was his expedition to the Cape of Good Hope to take observations of the heavens in the southern hemisphere. He remained there four years. His published results of his observations furnish one of the most valuable works on astronomy. He did not confine his studies to astronomy alone, but gave great attention to the subject of the atmosphere. He held that from eighty to ninety miles above the earth a perfect vacuum exists, and that three fourths of all the atmospheric air lies within four miles from the earth’s surface. His studies in meteorology were also very valuable, as well as his important discoveries in photography. Among his published works are: “Essays, from the Edinburgh and Quarterly Reviews, with Addresses and Other Pieces,” “Physical Geography,” and “Familiar Letters on Scientific Subjects.” Herschel held various positions of honor in his lifetime, being at one time president of the Royal Astronomical Society, and afterward Master of the Mint for five years. He was one of the eight foreign associates of the French Academy of Sciences.
[5.] “Fire Worshipers.” A Persian sect which worships fire as an emanation of the divine being. “Fire worshipers” is the English name for the Guēˈbers (also called Ghēˈber or Giaours—jours). They call themselves Beh Din, “those of excellent belief.” The Arabs completed the conquest of Persia in the seventh century, and the great mass of the nation adopted the faith of the conquerors. Those who refused to do so were subjected to persecution. Some of them took refuge in the wilderness of Khorasan, and others in Kohistan. The latter in the ninth century emigrated to India and settled in the neighborhood of Surat. Their descendants still inhabit the same region, and are called Parsees. The descendants of those who remained in Persia have gradually decreased in numbers and sunk into ignorance and poverty, though still preserving a reputation for honesty, chastity, industry, and obedience to law superior to that of the other Persians. They are estimated to number about 7,000.
[6.] “Bunsen Burner.” In this burner, at the lower end of the hollow stem through which the gas passes, there is a lateral orifice which admits the air necessary for combustion. This orifice can be made larger or smaller by means of a diaphragm which is used as a regulator. If a moderate amount of air enters, the gas burns with a luminous flame, but if a strong and steady current is admitted, the carbon is rapidly oxidized, the flame loses its brightness, and burns with a pale blue light, scarcely perceptible, and with intense heat.
[7.] “Voltaic Arc.” A most beautiful effect, obtained from the electric light. At the terminals of a battery, pieces of charcoal are connected and placed in contact until the current causes them to become incandescent. Then they are separated about the tenth of an inch, and it is found that a luminous, exceedingly brilliant arc connects the two points.
[8.] “Hell Gate.” The name of a narrow channel between Long Island and Manhattan Island. Until recently the numerous reefs made it impassable for large ships and dangerous for small ones. In 1851 the first efforts were made to open the channel, by submarine blasting. In 1876, after many vain attempts, the work was carried to a successful issue. The total amount of money expended by Congress for this work since 1868 was $1,940,000.
[9.] “Æolus.” A descendant of the founder of the Æolian race. He became the ruler of certain islands in the Tyrrhenian Sea, which from him were called the Æolian Islands. He is said to have taught his subjects to use sails on their ships, and to have foretold the nature of the winds that were to rise. Homer said of him that Jupiter had given him rule over the winds. This led to his being regarded as the god of the winds, which he was supposed to keep shut up in a mountain.