THE CONSTANT FACE OF THE MOON. 61 



incessantly operate until this adjustment had been effected, 

 and owing to the preponderating mass of the earth such 

 strenuous tides must have been evoked in the moon that 

 our satellite was brought under tidal control with compa- 

 rative facility. Hence it arose that in those early days 

 the habit of bending the same face incessantly towards 

 the earth around which it revolved was established on 

 our satellite. 



Time passed on, the moon gradually dispensed its 

 excessive heat by radiation into space, and it graduallj 

 became transformed from a molten globe to a globe with 

 a solid crust. It may be that the water was condensed 

 from vapour and then collected together into oceans on the 

 newly formed surface ; if so, these oceans would not have 

 any ebbing tide or flowing tide, for it would be constant 

 high tide at some places and constant low tide at others. 

 Such a state of things would at all events endure so long 

 as the adjustment of equality between the moon's rotation 

 and its revolution continued. In fact, should any depar- 

 ture from this adjustment have manifested itself corre- 

 sponding tides would have begun to throb in the lunar 

 oceans, and their tendency would be to restore the adjust- 

 ment which was disturbed. This arrangement between 

 the two movements was necessarily stable when tidal con- 

 trol was always at hand to check any tendency to depart 

 from it. 



It may be that the moon has now cooled so thoroughly 

 that not only is it hard and congealed on the exterior 

 as we see, but it seems highly probable that the heat 

 may have so entirely forsaken even the interior that 

 there is no longer any fluid in the globe of our satellite to 



