96) “From “100 Proofs the Earth is Not a Globe” by William Carpenter, “If we take a journey down the Chesapeake Bay, by night, we shall see the ‘light’ exhibited at Sharpe's Island for an hour before the steamer gets to it. We may take up a position on the deck so that the rail of the vessel's side will be in a line with the ‘light’ and in the line of sight; and we shall find that in the whole journey the light won't vary in the slightest degree in its apparent elevation. But, say that a distance of thirteen miles has been traversed, the astronomers' theory of ‘curvature’ demands a difference (one way or the other!) in the apparent elevation of the light, of 112 feet 8 inches! Since, however, there is not a difference of 100 hair's breadths, we have a plain proof that the water of the Chesapeake Bay is not curved, which is a proof that the Earth is not a globe.””

Botched experiment / incomprehension of geometry

The given numbers are only proof for a faulty experiment and don't even work on a flat earth. The only cited timeframe is the 1 hour between the light coming into view and the boat reaching it.

When Mr. Carpenter says that "in the whole journey the light won't vary in the slightest degree in its apparent elevation" that is just bullocks and again, is absolute geometrical nonsense even on a flat earth because also on a flat earth you have to look up more to a higher object as you get closer to it.

By the way, do you know the angular offset between a curved and a flat earth for an object that is 50m high and seen from sea-level at a distance of 25km (~16miles)? I did get into the hassle of measuring that with GeoGebra: It's 0.115°. And this value even gets smaller and smaller the closer you get to your target. That is just impossible to see with your bare eyes on a moving boat. Even if you brought a theodolite with you, you'd have quite a hard time measuring that.

http://200proofsearthisnotflat.blogspot.co.uk/2016/02/debunking-dubay-80-99200.html


A more recent debunking of similar claims by Mr Dubay here
https://www.metabunk.org/explained-443-km-distance-mountains-visible.t8980/#post-209201