The sun revolving on his axis turns, He tow'rs majestic through the spacious height; CHATTERTON. CONVERSATION VI. Of the Figure of the Earth. TUTOR. Having, in our last Conversation, given you a description of the Solar System in general, we will now proceed to consider each of its parts separately: and since we are most of all concerned with the earth, we will begin with that body. James. You promised to give us some reasons why this earth must be in the form of a globe, and not a mere extended plane, as it appears to common observation. Tutor. Suppose you were standing by the sea-shore, on a level with the water, and at a very considerable distance, as far as the eye can reach, you observe a ship approaching, what ought to be the appearance, supposing the surface of the sea to be a flat plane? Charles. We should, I think, see the whole ship at once, that is, the hull would be visible as soon as the top-mast. Tutor. It certainly must, or indeed rather sooner, because the body of the vessel being so much larger than a slender mast, it must necessarily be visible at a greater distance. James. Yes, I can see the steeple of a church at a much greater distance that I can discern the iron conductor which is upon it, and that I can perfectly see long before the little piece of gold wire, which is fixed at its extremity, is visible. Tutor. Well, but the top-mast of a vessel at sea is always in view some little time before the hull of the ves sel can be discerned. Now, if the surface of the sea be globular, this ought to be the appearance, because the protuberance or swelling of the water between the vessel and the eye of the spectator, will hide the body of the ship some time after the pendant is seen above. Charles. In the same way as if a high building, a church for instance, were situated on one side of a hill, and I was walking up on the opposite side, the steeple would come first in sight, and as I advanced towards the summit, the other parts would come successively in view. Tutor. Your illustration is quite to the purpose in the same way two persons, walking up a hill on the opposite sides, will perceive each other's heads first; and as they advance to the top, the other parts of their boIdies will become visible. With respect to the ship, the following figure will convey the idea very accurately. Suppose C A B represent a small part of the curved surface of the sea; if a spectator stand at B, while a ship is at C, only a small part of the mast is visible to hin, but as it advances, more of the ship is seen, till it arrive at e, when the whole will be in sight: Behold when the glad ship shoots from the port |