ASTRONOMY. 



towards the earth, and it appears full; 

 when the inoon is in conjunction with the 

 sun, its dark side is turned towards us, 

 and it is invisible. As it proceeds in its 

 orbit, a small part of the enlightened side 

 is seen, and then we have a nesv moon ; 

 and we continue to see more and more of 

 the enlightened side, as the moon ap- 

 proaches to the state of opposition, or full 

 moon. The waning or decreasing of the 

 moon takes place in the same manner, 

 but in a contrary order. The earth must 

 perform the same office to the moon that 

 the moon does to us ; and it will appear 

 to the inhabitants of the moon (if there be 

 any,) like a very magnificent moon, be- 

 ing to them about thirteen times as big as 

 the moon to us, and it will also have th e 

 same changes or phases. The moon's mo- 

 tion is subject to many irregularities, on 

 account of the inclination of its orbit to 

 the plane of the ecliptic, and the attrac- 

 tion of the sun and the other planets. 



Tke moon has scarcely any difference 

 ef seasons; her axis being almost perpen- 

 dicular to the ecliptic. What is very sin- 

 gular, one half of her has no darkness at 

 all, the earth constantly affording it a 

 strong light in the sun's absence ; while 

 the other half has a fortnight's darkness, 

 and a fortnight's light, by turns. Our 

 earth, as we have already observed, is un- 

 doubtedly a moon to the moon; waxing 

 and waning regularly, but affording her 

 13 times as much light as she does us. 

 When she changes to us, the earth ap- 

 pears full to her ; and when she is in her 

 first quarter to us, the earth is in its third 

 quarter to her ; and vice versa. But from 

 one half of the moon the earth is never 

 seen at all : from the middle of the other 

 half, it is always seen over head ; turning 

 round almost 30 times as quick as the 

 moon does. From the circle which limits 

 our view of the moon, only one half of 

 the earth's side next her is seen ; the 

 other half being hid below the horizon 

 of all places on that circle. To her, the 

 earth seems to be the biggest body in the 

 universe. As the earth turns round its 

 axis, the several continents, seas, and 

 islands, appear to the moon's inhabitants 

 like so many spots of different forms and 

 brightness moving over its surface ; but 

 much fainter at some times than others, 

 as our clouds cover them or leave them. 

 By these spots the Lunarians can deter- 

 mine the time of the earth's diurnal mo- 

 tion, just as we do the motion of the sun : 

 and perhaps they measure their time by 

 the motion of the earth's spots ; for they 

 cannot have a truer dial. The moon's 

 jcxis is so nearly perpendicular to the 



ecliptic, that the sun never removes sen- 

 sibly from her equator ; and the obliquity 

 of her orbit, which is next to nothing as 

 seen from the sun, cannot cause the' sun 

 to decline sensibly from her equator. 

 Yet her inhabitants are not destitute of 

 means for ascertaining the length of their 

 year, though their method and ours must 

 differ. For we can know the length of 

 our year by the return of our equinoxes : 

 but the Lunarians, having always equal 

 day and night, must have recourse to 

 another method ; and we may suppose 

 they measure their year, by observing 

 when either of the poles of our earth be- 

 gins to be enlightened, and the other to 

 disappear, which is always at our equi- 

 noxes, they being conveniently situated 

 for observing great tracts of land about 

 our earth's poles, which are entirely un- 

 known to us. Hence we may conclude, 

 that the year is of the same absolute 

 length both to the earth and moon, though 

 very different as to the number of days ; 

 we having 365} natural days, and the 

 Lunarians only 12_L, every day and night 

 in the moon being as long as 29| on the 

 earth. 



Mars is not so bright as Venus, nor 

 even as Jupiter, though nearer to the 

 sun. Its colour is a little reddish. Some 

 spots have been observed upon its sur- 

 face, from which its rotation round its 

 axis, and the inclination of its axis to the 

 plane of its orbit, have been determined. 

 This planet sometimes appears gibbous, 

 but never horned, like the moon, which 

 shews that his orbit includes that of the 

 earth, and that he shines by a borrowed 

 light. 



Ceres Ferdinandea is a very small pla- 

 net, situated next without Mars : it was 

 discovered on the first day of the present 

 century, by Mr. Piazzi, an Italian astro- 

 nomer. 



Pallas is another very small planet, dis- 

 covered by Dr. Olbers of Bremen, on the 

 28th of March, 1802. Two others have 

 also been discovered, one by M. Harding, 

 and the other by a pupil of Dr. Olbers. 

 To these have been given the names of 

 Juno and Vesta. These planets Dr. Hers- 

 chel proposes to call asteroids, because 

 they are so much smaller than any of the 

 other planets. 



Jupiter is the brightest planet next to 

 Venus. When viewed by a telescope, 

 several belts are observed across its disc, 

 parallel to its equator : these belts are va- 

 riable, and are supposed to be ranges of 

 clouds in the atmosphere of the planet. 

 Jupiter is surrounded by four moons, of 

 different sizes, which move about it in 



