THE MOON 363 



so, the consequent uniformity of her atmospheric tem- 

 perature from top to bottom greatly diminishes its re- 

 fractive qualities. 



You may wish to ask me why the moon does not ro- 

 tate, seeing that she was primevally provided with liquid 

 oceans. For this there are two reasons, either one of 

 which would suffice singly. One of these is, tftat the sat- 

 ellite's gravistatic heat is only a small fraction of the 

 earth's, being in fact only thirty degrees higher at the 

 depth of two miles than it is at, say, 100 feet below her 

 surface. The second reason is, that inasmuch as the lunar 

 oceans could never have exceeded a half mile in depth on 

 the average, and since the weight of water there is only 

 one-sixth of what it has here, the load on the bottom 

 waters could not have been more than fifteen atmospheres 

 and consequently fell far short of the amount requisite to 

 compress them beyond their freezing density. 



THE END. 



