484 THE POPULAR SCIENCE MONTHLY. 



Here, then, we have two remarkable consequences of the tides 

 which are inseparably connected. Remember, also, that we are not 

 enunciating any mere speculative doctrine. These results are the 

 inevitable consequences of the tides. If the earth had no seas or 

 oceans, no lakes or rivers ; if it were an absolutely rigid solid through- 

 out its entire mass then these changes could not take place. The 

 length of the day would never alter, and the distance of the moon 

 would only fluctuate between narrow limits. 



As thousands of years roll on, the length of the day increases sec- 

 ond by second, and the distance of the moon increases mile by mile. 

 These changes are never reversed. It is the old story of the perpetual 

 dropping. As the perpetual dropping wears away the stone, so the 

 perpetual action of the tides has sculptured out the earth and moon. 

 Still, the action of the tides continues. To-day is longer than yester- 

 day ; yesterday is longer than the day before. A million years ago 

 the day probably contained some minutes less than our present day 

 of twenty-four hours. Our retrospect does not halt here ; we at once 

 project our view back to an incredibly remote epoch which was a crisis 

 in the history of our system. 



Let me say at once that there is great uncertainty about the date 

 of that crisis. It must have been at least 50,000,000 years ago. It 

 may have been very much earlier. This crisis was the interesting 

 occasion when the moon was born. I wish I could chronicle the event 

 with perfect accuracy, but I can not be sure of anything except that 

 it was more than 50,000,000 years ago. 



I do not admit that there is anything discreditable about this un- 

 certainty. Do you not know that our historians, who have records 

 and monuments to help them, are often in great confusion about dates ? 

 I am not going to find any fault with historians. They do their best 

 to learn the truth ; but I can not help reminding you that they are 

 often as much in the dark about centuries as the astronomers are about 

 millions. Take, for example, the siege of Troy, which Homer has 

 immortalized, and ask the historians to state the date of that event. 

 Some say that the siege of Troy was 1184 b. c, others that it was 900 

 b. c. ; both are equally uncertain. Schliemann says that he found the 

 remains of the town burned down, but that no one knows who did it 

 or when it was done. Others, again, say that there was never any 

 siege of Troy at all. 



A recent instance which has attracted great and deserved attention 

 is Schliemann's discovery at Mycense of what he considers to have 

 been the tomb of Agamemnon. The tomb certainly did contain the 

 remains of some mighty man, if we may judge by the hundred-pound 

 weight of gold ornaments which wvre found there. Most people think 

 that these tombs, whosesoever they were, date from at least 1000 b. c. 

 On the other hand, some very high authorities regard the monuments 

 as the tombs of northern invaders who came into Greece 500-600 a. r>. 



