The Elements of Astronomy: A Text-book

Front Cover
 

What people are saying - Write a review

We haven't found any reviews in the usual places.

Other editions - View all

Common terms and phrases

Popular passages

Page 18 - ... is the great circle in which the plane of the earth's equator cuts the celestial sphere. It is often called the "Equinoctial.
Page 178 - The radius vector of each planet describes equal areas in equal times. (3) The squares of the periods of the planets are proportional to the cubes of their mean distances from the su» ; ie, £12 : ia2 : : «!3 : a28. This is the so-called "Harmonic Law.
Page 30 - FIG. 10. — Determination of Latitude. An exact definition of the astronomical latitude of a place has already been given (Art. 40). It is (1) the angle between the direction of gravity and the plane of the equator, which is the same as the altitude of the pole. (2) It may also be defined as the declination of the zenith, as is clear from Fig. 10, where PB, the altitude of the pole, equals QZ (since PQ and ZB are each 90°), and QZ by the very definition of declination (Art. 31) is the declination...
Page 219 - 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 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; Juno, Ceres, Vesta, and Pallas, grains of sand, in orbits of from 1000 to 1200 feet; Jupiter a moderate-sized orange...
Page 152 - The heat-unit most used at present is the " calory," l which is the quantity of heat required to raise the temperature of one kilogram of water 1° C. ; and as the result of the best observations thus far made...
Page iv - The eminence of Professor Young as an original investigator in astronomy, a lecturer and writer on the subject, and an instructor in college classes, led the publishers to present the General Astronomy with the highest confidence; and this confidence has been fully justified by the event.
Page iv - Certain subjects, which, while they certainly ought to be found within the covers of every text-book of Astronomy, are perhaps not essential to an elementary course, have been relegated to an appendix. Where time allows, the instructor will find it advisable to include some of them at least in the student's work. A brief Uranography is also presented, covering the constellations visible in the United States, with maps on a scale sufficient for the easy identification of all the principal stars. It...
Page 176 - Here, also, we find many writers, the older ones especially, bringing in the "projectile force," and saying that when a body moves in a curve, it does so " under the action of two forces ; one the force that draws it sideways, the other the 'projectile force' directed along its path." We repeat, this "projectile force" has no present existence nor meaning in the problem of a body's motion. Such a force may have put the body in motion long ago, but its function has ceased, and now we have only to...

Bibliographic information