PHYSIOLOGICAL PARADOXES. 



Very often, when the clouds lie in stream- 

 lines along the sky, it will be observed, on 

 looking at those which are low down near the 

 horizon, that there is a point on the horizon- 

 line from which all the cloud-lines in that half 

 of the sky seem to radiate, some sideways 

 and some upwards, much as suggested in 

 Fig. 52. If there are cloud-lines all over 

 the sky, the observer should turn round and 

 mark the part of the horizon exactly oppo- 

 site to this point of convergence. The second 



FIG. 52.-APPARENT CONVERGENCE OF CLOUD-LINES. 



point will also appear to be one towards which 

 all the cloud-lines in that half of the sky con- 

 verge. There are two such, one opposite to 

 the other. This phenomenon is not always 

 very plain. Sometimes the cloud-masses are 

 rounded, shapeless, indistinct, and not definitely 

 arranged in lines or streams. Yet even the 

 apparently irregular clouds will often be found, 

 on close observation, to be arranged in rows 

 or ranks ; and if these be regarded as the 

 cloud-lines, two opposite points of convergence 

 will be found, as described above. 



Where this arrangement of clouds is well 

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