ON THE APrEARA'NCES OF THE CELKSTIAL BODIES. 533 



hibit a very interesting object. The atmosphere of Venus is supposed to be 

 nearly like our own, or somewhat more rare. 



The inhabitants of the moon, if the moon is inhabited, must be capable of 

 living with very little air, and less water: there is reason to think their at- 

 mosphere less than a mile high, and it is never clouded: so that the sun must 

 shine without intermission for a whole fortnight on the same spot, without 

 having his heat moderated by the interposition of air, or by the evaporation 

 of moisture. The want of water in the moon is not, as some have supposed, 

 the necessary consequence of the want of an atmosphere; but it is inferred 

 partly from the total absence of clouds, and partly from the irregular ap- 

 pearance of the margin of the moon, as seen in a solar eclipse; no part of it 

 being terminated by a line sufficiently regular to allow us to suppose it the 

 surface of a fluid. The earth must always appear to occupy nearly the same 

 part of the sky, or rather to describe a small oval orbit round a particular 

 point, exposing a surface 13 times as great as that of the moon appears to us. 

 This large surface, suspended, with phases continually changing, like those 

 of the moon, must aiford, especially when viewed with a telescope, an ex- 

 cellent timepiece; the continents and seas coming gradually and regularly 

 into view, and affording a variety equally pleasing and useful. To us such 

 a timepiece would be of inestimable value, as it would afJbrd us an easy me- 

 thod of discovering the longitude of a place, by comparing its motion with 

 the solar time : but in the moon, the relative position of the earth and sun, 

 or of the earth and stars only, would be sufficient for determining the situation 

 of any place in sight of the earth ; if, however, there are no seas and no na- 

 vigation, astronomical observations of this kind would be of very little 

 utility. The assistance of the earth's phases in the measurement of time 

 might, however, still be very useful, for many purposes, to the inhabitants 

 of the nearer half of the moon ; and probably the remoter part is much de- 

 serted, for in their long night of half a month, they must be extremely in 

 want of the light reflected from the earth, unless the inhabitants have the 

 faculty of sleeping through the whole of their dark fortnight. The surface 

 of the moon appears to be very rocky and barren, and liable to frequent dis- 

 turbances from volcanos. These have been supposed to project some of their 

 contents within the 'reach of the earth's attraction, which they might easily 

 do, if they could throw them out with a velocity of about eight thousand feet 



