The Suez Canal was constructed in 1869. Like most things, it is proof of how flat the Earth is:
“8) The Suez Canal connecting the Mediterranean with the Red Sea is 100 miles long without any locks making the water an uninterrupted continuation of the two seas. When constructed, the Earth’s supposed curvature was not taken into account, it was dug along a horizontal datum line 26 feet below sea-level, passing through several lakes from one sea to the other, with the datum line and water’s surface running perfectly parallel over the 100 miles.”
I suppose what the author is trying to explain is that because a canal could be dug in such a way to make the surface of the water level, there is no way the Earth could be a ball. I would have to reference my discussion on how water flows (Water is Level) since it doesn’t matter if the reservoir for water is ocean, stream, or lake. With the construction of the Suez Canal, all that was needed was digging the same depth the entire length. This works regardless of a ball or flat Earth concept.