6fc [N STARRY REALMS. 



tides to accomplish great work in earlier stages of our globe's 

 history. 



As the evidence of the earth's crust proves that 

 our globe has lasted for incalculable ages, it becomes of 

 interest to think how far the gradual elongation of the day 

 may have attained significant proportions since very early 

 time. It may be that even in a thousand years the effect 

 of the tides is not sufficient to alter the length of the day 

 by so much as a single second. But the effect may be very 

 appreciable or even large in a million years, or ten million 

 vears. We have the best reasons for knowing that in 

 intervals of time comparable with those I have mentioned, 

 the change in the length of the day may have amounted 

 not merely to seconds or minutes, but even to hours. 

 Looking into the remote past, there was a time at which 

 this globe spun round in twenty-three hours instead of 

 twenty-four ; at a still earlier period the rate must have 

 been twenty hours, and the further we look back the more 

 and more rapidly does the earth appear to be spinning. 

 At last, as we strain our gaze to some epoch so excessively 

 remote that it must have been long anterior to those 

 changes which geology recognises, we see that our globe 

 was spinning round in a period of six hours or five hours, 

 or possibly even less. Here then is a lesson which the 

 tides have taught us : they liave shown that if the causes 

 at present in operation have subsisted without interruption 

 for a sufficiently long period in the past, the day must 

 have gradually grown to its present length from an initial 

 condition in which the earth seems to have spun round 

 about four times as quick!} 7 as it does at preseut. 



We should, however, receive a very inadequate im- 



