For more information about the sling go to:
http://slinging.org/
http://en.wikipedia.org/wiki/Sling_(weapon)
If you'd like to know more about the History of the Gatling Gun, go here: inventors.about.com/od/gstartinventions/a/Gatling_Gun.htm
Or, if you want to see more of the physics behind the first Gatling Gun, you can visit:
http://slinging.org/
http://en.wikipedia.org/wiki/Sling_(weapon)
If you'd like to know more about the History of the Gatling Gun, go here: inventors.about.com/od/gstartinventions/a/Gatling_Gun.htm
Or, if you want to see more of the physics behind the first Gatling Gun, you can visit:
Bibliography:
_Meltzer, Milton. Weapons & Warfare From the Stone Age to the Space Age. New York: Harper Collins Publishers, 1996.