ClipArt ETC
"Two cannon balls, when suspened by long cords, so as to hang quite near each other, are found to exert a mutual attaction, so that neither of the cords are excatly perpendicular, but they approach each other..." -Comstock 1850

Gravitational Attraction

"Two cannon balls, when suspened by long cords, so as to hang quite near each other, are found to exert…