FALSE PARALLELS. 



Well, the cloud lines being, within the limits 

 of human observation, parallel, they come 

 under the law of perspective which has been 

 referred to, and so, to our eyes, they appear to 

 approach one another as they recede from us. 

 Now, they are nearest to us where they are 

 directly overhead ; and here they look fairly 

 parallel. Forwards and backwards, as the dis- 

 tance increases, they seem to draw nearer to- 

 gether, till, as they approach the horizon, the 



B 



A c 



FlG. 54. THE SPHERICAL SHAPE OF THE CLOUD FIRMAMENT 



ends of the lines appear to converge towards a 

 point not far beyond it. 



Hence their apparent arrangement like the 

 leaves of an opened fan. 



In the case of the clouds this effect is in- 

 tensified by the fact that the ends of the lines 

 are actually lower than the middle. If the 

 cloud firmament were a plane, perfectly flat and 

 level, under the law of perspective, its edges, 

 with the ends of the cloud lines, would appear 

 nearer to the horizon than their middle part 

 does to the earth's surface. But the cloud 

 firmament, ABC, in Fig. 54, is not a plane, 

 but a spherical outline, concentric with the 

 spherical surface of the earth, D E F ; and it 

 actually does cut the horizon-line G E H. The 

 e 241 



