Chapter II. Experiments Demonstrating the True Form of Standing Water, and Proving the Earth to be a Plane
Rowbotham starts his Experiments chapter with an introduction to the Drop = 8 x (distance in miles)^2 rule. See below. The actual experiments can be found from page 2 onward.
Page 2: The Old Bedford Level (Experiment 1)
Page 3: The Old Bedford Level (Experiment 2)
Page 4: The Old Bedford Level (Experiment 3)
Page 5: The Old Bedford Level (Experiment 4)
Page 6: The Old Bedford Level (Experiment 5)
Page 7: Brighton Pier (Experiment 6)
Page 8: The Sea Horizon (Experiment 7)
Page 9: The Sea Horizon (Experiment 8)
Page 10: St. George’s Channel (Experiment 9)
Page 11: Balloon (Experiment 10)
Page 12: Brighton Eastern Pier (Experiment 11)
Page 13: Waterloo, Liverpool (Experiment 12)
Page 14: North-Western Railway (Experiment 13)
Page 15: Shooter’s Hill, Kent (Experiment 14)
Page 16: Grand Hotel, Brighton (Experiment 15)
8 Inches Rule of Thumb
Flat Earth believers often quote the “8 inches rule” rule when discussing “the supposed curvature” of the Earth.
IF the earth is a globe, and is 25,000 English statute miles in circumference, the surface of all standing water must have a certain degree of convexity–every part must be an arc of a circle. From the summit of any such arc there will exist a curvature or declination of 8 inches in the first statute mile. In the second mile the fall will be 32 inches; in the third mile, 72 inches, as shown in the following diagram:
In every mile after the first, the curvature downwards from the point T increases as the square of the distance multiplied by 8 inches. The following table will show at a glance the amount of curvature, in round numbers, in different distances up to 100 miles.
Curvature in 1 statute mile: 8 inches.
Curvature in 10 statute miles: 66 feet.
Curvature in 20 statute miles: 266 feet.
Curvature in 30 statute miles: 600 feet.
Curvature in 40 statute miles: 1066 feet.
Curvature in 50 statute miles: 1666 feet.
Curvature in 60 statute miles: 2400 feet.
Curvature in 70 statute miles: 3266 feet.
Curvature in 80 statute miles: 4266 feet.
Curvature in 90 statute miles: 5400 feet.
Curvature in 100 statute miles: 6666 feet.
It will be seen by this table that after the first few miles the curvature would be so great that no difficulty could exist in detecting either its actual existence or its proportion.
On the next couple of pages Rowbotham will show a number of experiments attempting to detect curvature. Failing to detect any curvature, his conclusion was the Earth must be flat.
How accurate is the 8 inches rule?
The 8 inches rule was used by land surveyors, who measure distances between two points that are relatively close together. In these situations the discrepancy over larger distances was never an issue. But when you compare the rule of thumb results to the real numbers you will notice the discrepancy when going beyond 100 miles or so. Even Rowbotham mentioned “The rule, however, requires to be modified after the first thousand miles.” To showcase the error I created the following image using an Excel sheet:
What is the real formula for curvature drop?
The actual formula is: drop = (SQRT (radius^2 + distance^2)) – radius.
For an overview of different formulas for curvature drop, please check the following Youtube video: https://www.youtube.com/watch?v=pFxsjOqY-xQ