. Astronomy for students and general readers . avenly bodies,but because it is from its surface that all observations ofthe heavens have to be made. A consideratioji of well-known facts will show that thisearth upon which we live is, at least approximately, aglobe whose dimensions are giganticwhen compared to our ordinary anddaily ideas of size. Its shape is inseveral ways known to be nearlythat of a sphere. I. It has been repeatedly circum-navigated in various directions. II. Portions of its sin-face, visi-ble from elevated positions in themidst of extensive plains or at sea,appear to be boun
. Astronomy for students and general readers . avenly bodies,but because it is from its surface that all observations ofthe heavens have to be made. A consideratioji of well-known facts will show that thisearth upon which we live is, at least approximately, aglobe whose dimensions are giganticwhen compared to our ordinary anddaily ideas of size. Its shape is inseveral ways known to be nearlythat of a sphere. I. It has been repeatedly circum-navigated in various directions. II. Portions of its sin-face, visi-ble from elevated positions in themidst of extensive plains or at sea,appear to be bounded by appearance at all points of the niusu-ating the fact that the .« !!• ,.1 portions of the eartti visible suiiace of a body is a geometrical from elevated positions, s, s, ., ., , J. T 1 1 J- 1 S, etc., are bounded by circles. attnbute oi a globular form only. III. Further than this we know that careful measure-ments of portions of the globe by the various nationalgeodetic surveys have agreed with this general Pig. 3. 10 ASTRONOMY. More precise reasons will be apparent later, bnt these willbe sufficient to base our general considerations upon. Ofthe size of the earth we may form a rough idea by thetime required to travel completely around it, which isnow about three months. We find next that this globe is completely isolatedin space. It neither rests on any thing else, nor is it incontact with any surrounding body. The most obviousproof of this which presents itself is, that mankind have^isited nearly every part of its surface without findingany such connection, and that the heavenly bodies seemto perform complete circuits around it and under it with-out meeting with any obstacles. The sun which rose to-day is the same body as the setting sun of yesterday, butit has been seen to move (apparently) about the earthfrom east to west during the day, and it regularly reap-pears each morning. Moreover, if attentively watched,it will be found to rise a
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