Part 1

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POPULAR

LESSONS IN ASTRONOMY,

ON A NEW PLAN;

WHICH SOME OF THE LEADING PRINCIPLES OF THE SCIENCE ARE ILLUSTRATED BY ACTUAL COMPARISONS, INDEPENDENT OF THE USE OF NUMBERS.

FRANCIS J. GRUND,

AUTHOR OF “AN ELEMENTARY TREATISE ON PLANE AND SOLID GEOMETRY,” “ELEMENTS OF NATURAL PHILOSOPHY AND CHEMISTRY,” &c.

BOSTON

CARTER, HENDEE AND CO.

1833.

ENTERED according to Act of Congress, in the year 1833, By FRANCIS J. GRUND, in the Clerk’s office of the District Court of Massachusetts.

I. R. BUTTS, SCHOOL STREET.

NOTICE.

The Geographical Miles, which are used in the scales and tables of this book, are German Geographical Miles, of which 15 make one degree. The teacher or pupil may easily change them into English Geographical Miles, by multiplying them by 4, the square miles by 16, and the cubic miles by 64.

PREFACE.

Although many elementary works on Astronomy are already before the public, yet it is believed there is none in which the various magnitudes, surfaces, and distances of the heavenly bodies, are presented to the eye of the learner by actual comparisons;—the only way, perhaps, in which young pupils can be expected to form a correct idea of them. This the author has attempted in the following pages. The comparative diameters, surfaces and distances of the different planets, are all drawn, in the plates, according to a fixed scale of geographical miles; the surfaces of the planets are actually reduced to square measure, and drawn in proportion to each other and the sun; so that the youngest pupil, by a mere glance of the eye, is enabled to form a correct idea of their respective magnitudes. A similar plan has been pursued, in regard to the division of the Earth into Zones, and with respect to the extent of the five great Continents of our Globe. The Appendix contains an exposition of the population of America, Europe, Asia, Africa, and Australia, accompanied by a plate for the illustration of the comparative settlements on those Continents.

Boston, June 24, 1833.

POPULAR LESSONS IN ASTRONOMY.

LESSON I.

THE EARTH IN ITS RELATION TO THE SUN, MOON AND STARS.

§ 1. The Earth on which we live, and on which plants, trees and animals successively live and die, is only a small part of the world; it is but one of the smallest bodies in the Universe. To the world belong yet the Sun from which we receive warmth and light, the Moon, and an innumerable class of bodies, which, at night, appear to us as so many points of light. These are called Stars.

The reason why the Stars appear to us so small, is because they are so far from us; and things appear smaller in proportion as they are farther removed from us. This you will have noticed, when looking from a high steeple on the people below, or on a vessel far out in the harbour, or on a chain of mountains at a great distance.

§ 2. Most all Stars appear to us, every night in the same position; they seem actually to be fixed in the heavens; and for this reason they are called fixed Stars. There are however Ten others, of which it has been ascertained that they move regularly round the Sun in large circles. These are called Planets or wandering Stars.—The fixed Stars are supposed to be similar to the Sun, in as much as they are bodies which have their own light. The Planets, on the contrary, are of themselves dark bodies, and receive, like our Earth, light and warmth from the Sun. We see them only in consequence of the solar light which they reflect from their surfaces, and this is the reason why they appear to us as bright as the other Stars.

§ 3. The discoveries of Philosophers have proved beyond a doubt, that our Earth itself is one of those Planets, which move round the Sun in stupendous large circles, whose grandeur is hardly conceived by the most powerful imagination. Our Earth, therefore, is, itself, a Wandering Star, and the line in which it moves round the Sun is called its Way or Orbit.

§ 4. The Planets, together with our Earth keep each a certain fixed distance from the Sun. On this account they do not disturb each other in their orbits. But they vary from each other in magnitude; although all of them (consequently also our Earth) have a round shape, similar to a ball.

In former times men believed that the Earth was flat, or a circular plate on all sides surrounded by water. But this is not true. For it has been proved by a great many observations and actual measurements, that the Earth has a spherical (ball-like) form. Moreover there are navigators who have actually sailed round the world, and who have noticed the fact that at sea, the tops of distant objects are seen sooner than the rest; which again proves the spherical form of our Earth. For an illustration you may look at the adjoining plate Plate No. I.

The man who is represented as standing on a portion of our Earth, will at first only see the topmast of a vessel at sea; when she comes nearer his eye will discover a much greater portion of her; but when in the third position every part of the vessel will be visible.

§ 5. Some of the Planets are, in their motion round the Sun, accompanied by other dark bodies, which, like the Planets themselves, receive light and heat from the Sun. These are called Satellites or Moons. Such a Satellite is the Moon which accompanies our Earth; and there are Planets (as we shall see hereafter) which have Four and Six, and One that has even Seven Moons.