GEOLOGY. 



When we aft our eyes towards the sky, we 

 perceive an apparent hollow hemisphere, placed 

 at an indefinite distance, and surrounding the 

 earth en every hand. In the day time, the prin 

 cipal object which appears in the hemisphere, is 

 the sun. In the morning, we see him rise above 

 the distant mountains, or from the extremity of 

 the ocean; he gradually ascends the vault of 

 heaven, and then declines, and disappears in the 

 opposite quarter of the sky. In the northern 

 parts of the globe, where we reside, if about the 

 21st of March, we place ourselves on an open plain, 

 with our face towards the south, the sun will 

 appear to rise on our left, or due east, about six 

 in the morning, and about the same hour in the 

 evening, he will set due west. In the month of 

 June he rises to our left, but somewhat behind 

 us, in a direction towards the north-east, ascends 

 to a greater height at noon than in the month of 

 March, and, after describing a large arc of the 

 heavens, sets on our right, and still behind us, in 

 the north-western quarter of the sky. In the 

 month of December, if we stand in the same 

 position, we may observe, without turning our 

 selves, both his rising and setting. He rises in 

 the south-east, ascends to a small elevation at 

 noon, and sets in the south-west, after having 

 described a very small arc of the heavens. Every 

 day he appears to move a little towards the east, 

 or contrary to his apparent diurnal motion ; for 

 the stars which are seen to the eastward of him, 

 appear every succeeding day to make a nearer 

 approach to the place in which he is seen. All 

 the variety of these successive changes is accom 

 plished within4he period of 365 days 6 hours, in 

 which time he appears to have made a complete 

 revolution round the heavens from west to east. 



The moon is the next object in the heavens 

 which naturally attracts our attention ; and she is 

 found to go through similar variations in the course 

 of a month. When she first becomes visible at 

 new moon, she appears in the western part of 

 the heavens, in the form of a crescent, not far 

 from the setting sun. Every night she increases 

 in size, and removes to a greater distance 

 from the sun, till at last, she appears in the east 

 ern part of the horizon, just as the sun disap 

 pears in the western ; at which time she presents 

 a round full-enlightened face. After this, she 

 gradually moves farther and farther .eastward, 

 and her enlightened part gradually decreases, till 

 at last she seems to approach the sun as nearly 

 in the east as she did in the west, and rises only 

 a little before him in the morning, in the form of 

 a crescent. All these different changes may be 

 traced by attending to her apparent positions, 

 from time to time, with respect to the fixed stars. 



A dark shadow is occasionally seen to move 

 across the face of the moon, which obscures 

 her light, and gives her the appearance of tar- 

 tished copper. Sometimes this shadow covers 

 ar y a small portion of her surface ; at other 



times it covers the whole of her disk for an nour 

 or two, and its margin always appears of the 

 figure of a segment of a circle. This phenome 

 non, which happens, at an average, about twice 

 every year, is termed an eclipse of the moon. It 

 is produced by the shadow of the earth falling 

 upon the moon, when the sun, the earth, and the 

 moon, are nearly in a straight line; and can 

 happen only at the time of full moon. Some 

 times the moon appears to pass across the body 

 of the sun, when her dark side is turned towards 

 the earth, covering his disk either in whole or in 

 part, and intercepting his rays from a certain 

 portion of the earth. This is called an eclipse 

 of the sun, and can happen only at the time of 

 new moon. In a total eclipse of the sun, which 

 seldom happens, the darkness is so striking, that 

 the planets, and some of the larger stars, are dis 

 tinctly seen, and the inferior animals appear 

 struck with terror. 



Again, if, on a winter s evening, about six 

 o clock, we direct our view to the eastern quar 

 ter of the sky, we shall perceive certain stars 

 just risen above the horizon : if we view the 

 same stars about midnight, we shall find them at 

 a considerable elevation in the south, having 

 apparently moved over a space equal to one half 

 of the whole hemisphere. On the next morning, 

 about six o clock. the same stars will be seen set 

 ting in the western part of the sky. If we tumour 

 eyes towards the north, we shall perceive a simi 

 lar motion in these twinkling orbs, but with this 

 difference, that a very considerable number of 

 them neither rise nor set, but seem to move 

 round an immoveable point, called the north 

 pole. Near this point is placed the polar star, 

 which seems to have little or no apparent motion, 

 and which, in our latitude, appears elevated a 

 little more than half way between the northern 

 part of our horizon and the zenith or point above 

 our heads. A person who has directed his 

 attention to the heavens for the first time, after 

 having made such observations, will naturally in 

 quire Whence come those stars which begin to 

 appear in the east ? Whither have those gone, 

 which have disappeared in the west? and, what 

 becomes, during the day, of the stars which are 

 seen in the night? It will soon occur to a ra 

 tional observer, who is convinced of the round 

 ness of the earth, that the stars which rise above 

 the eastern horizon come from another hemis 

 phere, whicn we are apt to imagine below us, 

 and when they set, return to that hemisphere 

 again ; and, that the reason why the stars are 

 not seen in the day-time, is, not because they 

 are absent from our hemisphere, or have ceased 

 to shine, but because their light is obscured by 

 the more vivid splendour of the sun.* From such 



This is put beyond all doubt, by the invention of 

 the telescope ; by which instrument, adapted to an 

 equatorial motion, we are enabled to see many of 

 the stars even at noon-day. The Author of thia 



