Overwhelming evidence? Ha!
Even in Rowbotham's day, the idea of a Round Earth was as dogmatic as stone. A whirl of constantly changing fact and conjecture which were systematically brainwashed into children from the age of three.
Here is a direct quote from Dr. Rowbotham:
"It is ... candidly admitted that there is no direct and positive evidence that the world is round, that it is only 'imagined' or assumed to be do in order to afford an explanation of 'scores of phenomena'. This is precisely the language of Copernicus, of Newton, and of all astronomers who have labored to prove the rotundity of the earth, It is pitiful to the extreme that after so many ages of almost unopposed indulgence, philosophers instead of beginning to seek, before anything else, the true constitution of the physical world, are still to be seen laboring only to frame hypotheses, and to reconcile phenomena with imaginary and ever-shifting foundations. Their labor is simply to repeat and perpetuate the self-deception of their predecessors."
Rowbotham, a notable astronomer and medical doctor, believed that Newtonian astronomy was a 'juggle and a jumble of fancies and falsehoods; an elaborate theoretical trick ' enough to make the unprejudiced observer revolt with horror from the terrible conjunction which has been practiced upon him'.
In the face of this elitist conspiracy, the only solution, Rowbotham declared, was to replace conventional science with a true and practical free-thought method. He promoted as a back-to-basics approach to knowledge, in which experiments were tried and facts were collected not only to corroborate any existing theory but to start from scratch to uncover the great universal and primary truths.
A man well ahead of his time, Rowbotham's life work and inquiry was able to predict the movements of the continents one hundred years before tectonic plate shifting was discovered. He was able to accurately and mathematically predict lunar eclipses, the tides, and a number of phenomena in his model of the Earth. He also published a book called Zetetic Astronomy which accurately explained the movements of the stars and completely rewrote Newtonian mechanics from the ground up.
Besides his honest investigation to the true shape of the earth, Rowbotham patented safety mechanisms for trains, vulcanized rubber, nutritional elixirs, and a number of other notable inventions. As a true Zetetic, Rowbotham did not simply make theories while sitting in a closet like Newton and Copernicus. Dr. Rowbotham used his wealth to sail the world in his life-long study of the earth and the cosmos.
The Flat Earth Society wasn't just a bunch of crackpots as you might have been led to believe. At one point there were thousands of Flat Earth proponents, located in all parts of the world. Businessmen, seamen, pilots, lawyers, physicists, astronomers, and even Nobel Prize winners. This continued well after the Apollo missions. There was even an entire city in America founded upon the beliefs of a Flat Earth. The Flat Earth Society even had its own dedicated 50,000 watt radio station which promoted the the flat out truth to the American public. Over its colorful 150 year history the truth of the Flat Earth spread so far and wide that today there are entire countries in Polynesia which believe in a Flat Earth.
It's all gone now, however. Since the arson of the central FES library and the gradual offing of its presidents, the society has been on a slow decline.