We have seen that at the present moment the day is becoming gradually longer and the moon is steadily receding further and further from the earth. At present these changes take place with extreme slowness, but in the primitive periods of which we have already spoken, the changes in the length of the day, and the changes in the distance of the moon, proceeded at a rate far more rapid than at present. As the moon has receded further from the earth its efficiency as a tide-producer has declined, and consequently the rate at which the consequences of tidal action have proceeded is continually lessening. It must therefore be expected that the progress of tidal evolution in the future will be ever getting slower and slower, so that the periods of time required for the further development of the phenomena far exceed those which have elapsed in the course of the history already given. We can, however, foreshadow what is to happen in the following manner. The length of the day will slowly increase; and we can indicate a state of things in the excessively remote future toward which it may be said the system is tending. The day will grow until it becomes not merely twenty-five or twenty-six hours, but until it becomes as long as two or three of our present days. In fact, as we stretch our imagination through ages so inconceivable that I forbear to specify any figures which might characterize them, we seem to discern that the length of the day may go on ever getting longer and longer until at last a stage is reached when the day is about fifty or sixty times as long as our present day. All this time, in accordance with the general law of action and reaction, the moon must be gradually retreating. As the orbit of the moon is gradually enlarging, the time that the moon takes to revolve around the earth must be continually on the increase; from the present month of twenty-seven days the length of the month will gradually augment as the ages roll by until at last when the moon has reached a certain distance the period of its rotation will have become double what it is at present, or indeed rather more than double, and we shall have the day and the month equal, each being about fourteen hundred hours long. When this state of things is reached, the earth will always turn the same face toward the moon, just as the moon at present always turns the same face toward the earth.