Brokenpole and Max, those are fine photos of an 8-inch Model of 1844 Columbiad mounted on a Federal siege carriage, and I'm with Cannonmn, I've also never seen one of these cannon mounted on this type of carriage before, but live and learn.
I'll place this addendum here, so this post will at least serve some purpose.
8-inch Columbiad, Model of 1844. Nominal length, 119 inches; weight, 9,200 pounds; total production, 315; known survivors, 21. While designated a "columbiad," this model has a chamber and was classified as a seacoast howitzer, firing shell only.
M1844, 8-inch Columbiad located by the Navy Memorial at the National Military Park, Vicksburg, MS.
Manufactured by Fort Pitt Foundry, U.S. registry no. 59, Inspected by Edward Harding, cast in 1846, Weight is 9,140 lbs, metal is iron.
Thank You, Mr. Wayne Stark.