64) “Quoting “Earth Not a Globe!” by Samuel Rowbotham, “It is known that the horizon at sea, whatever distance it may extend to the right and left of the observer on land, always appears as a straight line. The following experiment has been tried in various parts of the country. At Brighton, on a rising ground near the race course, two poles were fixed in the earth six yards apart, and directly opposite the sea. Between these poles a line was tightly stretched parallel to the horizon. From the center of the line the view embraced not less than 20 miles on each side making a distance of 40 miles. A vessel was observed sailing directly westwards; the line cut the rigging a little above the bulwarks, which it did for several hours or until the vessel had sailed the whole distance of 40 miles. The ship coming into view from the east would have to ascend an inclined plane for 20 miles until it arrived at the center of the arc, whence it would have to descend for the same distance. The square of 20 miles multiplied by 8 inches gives 266 feet as the amount the vessel would be below the line at the beginning and at the end of the 40 miles.””

This is exactly the same as Point 60, the plank experiment. This time, instead of a plank it is a piece of string. As we've already discussed at length, you can't observe the horizon being curved below a rather high height.

The horizon on a sphere forms a circle of equal relative altitude to your point of observation. When you look at it from low altitudes, you see nothing but a line and any ship going along the horizon doesn't have to go up or down (not even by a nanometer) as seen from your point of view.

As GreaterSapien points out in his debunk of this point, neither Dubay nor any of his followers have every tested this themselves. But others have.

In fact, this experiment has been conducted several times, each time showing the curve of the horizon.

All of these tests showed the falsity off Dubay’s claim.

Rory reported his tests with the straight level he jokingly called the Horizonomatic 5000

 

https://www.metabunk.org/threads/how-to-take-a-photo-of-the-curve-of-the-horizon.8859/page-2

 

And at 

https://www.metabunk.org/threads/measuring-the-curvature-of-the-horizon-with-a-level.7832/page-4

 

Reported  here by MCToon 

 

https://mctoon.net/left-to-right-curve/

 

And Rory’s findings were replicated by debunker Bobby Shafto, here;

Finding the Curve

https://youtu.be/KWUAuAvzxyc