Not content with merely admitting the idea of the earth’s motion as a simple arbitrary hypothesis, which several astronomers had done before him, he wished--and this is his glory--to demonstrate it to himself by acquiring the conviction by study, and wrote his book to prove it. The true prophet of a creed, the apostle of a doctrine, the author of a theory, is the man who, by his works, demonstrates the theory, makes the creed believed in, and spreads the doctrine. He is not the creator. “There is nothing new under the sun,” says an ancient proverb. We may rather say, Nothing which succeeds is entirely new. The newborn is unformed and incapable. The greatest things are born from a state of germ, so to say, and increase unperceived. Ideas fertilize each other. The sciences help each other; progress marches. Men often feel a truth, sympathize with an opinion, touch a discovery, without knowing it. The day arrives when a synthetical mind feels in some way an idea, almost ripe, becoming incarnate in his brain. He becomes enamored of it, he fondles it, he contemplates it. It grows as he regards it. He sees, grouping round it, a multitude of elements which help to support it. To him the idea becomes a doctrine. Then, like the apostles of good tidings, he becomes an evangelist, announces the truth, proves it by his works, and all recognize in him the author of the new contemplation of nature, although all know perfectly well that he has not invented the idea, and that many others before him have foreseen its grandeur. Such is the position of Copernicus in the history of astronomy. The hypothesis of the earth’s motion had been suggested long before his birth on this planet. This theory counted partisans in his time. But he--he did his work. He examined it with the patience of an astronomer, the rigor of a mathematician, the sincerity of a sage, and the mind of a philosopher. He demonstrated it in his works. Then he died without seeing it understood, and it was not till a century after his death that astronomy adopted it, and popularized it by teaching it. However, Copernicus is really the author of the true system of the world, and his name will remain respected to the end of time. The so-called “seas” on the moon are those large dark spots to be seen on its surface, in the shape of “eyes, nose, and mouth,” or of the famous old man with his bundle of sticks. The brighter parts are the more mountainous parts. The chief ranges of lunar mountains have been named by astronomers after mountains on earth, such as the Apennines, the Alps, the Caucasian range, the Carpathian and the Altai Mountains. CHAPTER XVI. MERCURY, VENUS, AND MARS. Once again we have to journey through the high-roads of the Solar System, paying a brief visit to each in turn of our seven chief brother-and-sister planets, and learning a few more leading facts about them. Having gone the same way before, it will not now seem quite so far.