StoopStoop wrote:
> I measured the cannonball with a string and the string was 13 inches long, do I divide that by 3.14 to get the measurement?
Because hundredths-of-an-inch are extremely important in authenticating an iron ball as a cannonball (or not), it's better to use 3.1416 when mathematically calculating the ball's diameter.
Using a string and measuring it will get you an "in the ballpark" number ..but even a 1/4-inch error in measuring the string will produce a significantly incorrect calculation.
That having been said, let's do the calculation with the measurement you've given: the ball's circumference is 13.0 inches, divided by Pi 3.1416 equals diameter 4.138 inches. Let's call that 4.14 inches ...which is larger than a 9-pounder Solid-Shot's prescribed diameter of 4.10 inches. So, either your iron ball is not a cannonball, or your measuring is incorrect, or the ball's diameter is inceased by rust-concretion on the ball's surface.
StoopStoop also wrote:
> There is a flatish spot on one side of the iron ball and on the exact opposite side.
> The side with the seam is round and that's what I measured.
> Are the file markings on the seam any clue?
I know you've put the ball up for sale on Ebay as part of a Charity auction. Threfore, please believe me that I take no pleasure in having to tell you, those two characteristics (flat-ish areas on opposite sides of the ball, and file markings on the seam) definitely disqualify it from being a cannonball.
For your own certainty:
Closely examine photos of properly-authenticated cannonballs -- not the ones on Ebay, but at authoritative sites such as civilwarartillery.com and the photos in my book "Field Artillery Projectiles of the American Civil War." You will see that NO actual cannonballs have flat-ish areas. Although some have a visible mold-seam, their body is perfectly round as a ball-bearing or a glass marble. The flat-ish areas on your iron ball mean it is out-of-round, so it is not a cannonball.
About the file-marks:
During metal-casting, there typically will be a tiny amount of "seepage" by the molten metal into the mold's seam (where the two halfs of the mold are put together). When that happens, it is neccesary for a Foundryworker to remove the casting-seepage iron from the ball's seam-line after it cools and comes out of the mold. During the civil war (and earlier), that work was ALWAYS done with chisel -- NEVER a file ...nor, a grinding-wheel. File-marks or grinder-marks on an iron ball mean it is not a cannonball.
If you are in doubt that what you said are file-marks really are file-marks, please use the Macro setting on your camera's controls and take some super-closeup photos of the marks, and post those photos here.
Regards,
Pete