## An Explanation of the Gnomonic Projection of the Sphere; and of Such Points of Astronomy as are Most Necessary in the Use of Astronomical Maps: Being a Description of the Construction and Use of the Larger and Smaller Maps of the Stars; as Also of the Six Maps of the Earth |

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according angle appear applied astronomical axis body called catalogue centre circle complete cone considered constellations constructed contains cube declination described determined direction distance divided double stars draw drawn earth ecliptic effect ellipse equal equator equinox figure fixed four give given globe greater Greenwich half hand heavens Herschel horizon hour hour circle known latitude latter length light longitude look magnitude marked means measuring meet meridian method micrometer minutes motion move nearly nebulæ objects observations opposite orbit parallel pass plane polar pole portion position preceding present projection proper Ptolemy published question relative remaining remarkable represented right ascension round seen side solar solstice space spectator sphere sufficient suppose surface taken telescope turned various visible whole wire

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Page 27 - The circumference of every circle is supposed to' be divided into 360 equal parts, called degrees ; each degree into 60 minutes, and each minute into 60 seconds. Degrees, minutes, and seconds are designated by the characters °, ', ". Thus 23° 14' 35" is read 23 degrees, 14 minutes, and 35 seconds.

Page 92 - To imitate the motions of the planets in the above-mentioned orbits, Mercury must describe its own diameter in 41 seconds; Venus in 4 minutes 14 seconds ; the Earth in 7 minutes ; Mars in 4 minutes 48 seconds ; Jupiter in 2 hours 56 minutes; Saturn in 3 hours 13 minutes; and Uranus in 2 hours 16 minutes.

Page 92 - On it place a globe, two feet in diameter ; this will represent the Sun ; Mercury will be represented by a grain of mustard seed, on the circumference of a circle 164 feet in diameter for its orbit ; Venus a pea, on a circle of 284 feet in diameter ; the Earth also a pea, on a circle of 430 feet ; Mars a rather large pin's head, on a circle of 654 feet ; the Asteroids, grains of sand, in orbits of from 1000 to 1200 feet; Jupiter a moderate-sized orange, in a circle nearly half a mile across...

Page 92 - Mars a rather large pin's head, on a circle of 654 feet; Juno, Ceres, Vesta, and Pallas, grains of sand, in orbits of from 1000 to 1200 feet; Jupiter a moderate-sized orange, in a circle nearly half a mile across; Saturn a small orange, on a circle of four-fifths of a mile; Uranus a full-sized cherry, or small plum, upon the circumference of a circle more than a mile and a half, and Neptune a good-sized plum on a circle about two miles and a half in diameter.

Page 105 - Figs. 11—12. of large stars, into which the central cluster would be seen projected, and (owing to its greater distance) appearing, like it, to consist of stars much smaller than those in other parts of the heavens.

Page 105 - ... of large stars, into which the central cluster would be seen " projected, and (owing to its greater distance) appearing, like it, to " consist of stars much smaller than those in other parts of the heft" vens. Can it then be that we have here a real brother system, " bearing a real physical resemblance and strong analogy of structure

Page 92 - As to getting correct notions on this subject by drawing circles on paper, or still worse, from those very childish toys called orreries, it is out of the question.

Page 53 - Imagine that Jupiter, fearing to come too nigh unto her teeth, layde holde on her tayle, and thereby drewe her up into the heaven ; so that shee of herself being very weightie, and the distance from the earth to the heavens very great, there was great likelihood that her taile must stretch. Other reason know I none.