Watch The Horizon Is Always Flat video on DTube
If we stand on the sands of the sea-shore and watch a ship approach us, we shall find that she will apparently "rise" - to the extent, of her own height, nothing more. If we stand upon an eminence, the same law operates still; and it is but the law of perspective, which causes objects, as they approach us, to appear to increase in size until we see them, close to us, the size they are in fact. That there is no other "rise" than the one spoken of is plain from the fact that, no matter how high we ascend above the level of the sea, the horizon rises on and still on as we rise, so that it is always on a level with the eye, though it be two-hundred miles away, as seen by Mr. J. Glaisher, of England, from Mr. Coxwell's balloon. So that a ship five miles away may be imagined to be "coming up" the imaginary downward curve of the Earth's surface, but if we merely ascend a hill such as Federal Hill, Baltimore, we may see twenty-!five miles away, on a level with the eye - that is, twenty miles level distance beyond the ship that we vainly imagined to be " rounding the curve," and "coming up!" This is a plain proof that the Earth is not a globe.
