The Spar deck battery of the "Trenton" consists of two eight inch converted Rifles on the forecastle, and one aft. The forward guns are mounted on Ericsson pivot carriages, shifted and trained by tackles. The recoil is controlled by friction compressors, attached to the front of the top carriages. Attached to each slide are two bronze compressor plates, the length of the recoil allowed, placed horizontally, one above the other. The gun is run in or out by direct gearing on the inside of the brackets of the top carriage, which is geared into a longitudinal rack, inside of and close up to one of the rails of the slide. The rear trucks of the top carriage are on eccentric axles, but the depth of the cogs of the gearing is sufficient to prevent their being entirely separated by heaving the rear trucks into action. These forward guns can be fired both on the same side of the ship, or one on either side. They can be trained from right ahead to about two points abaft the beam. The after pivot gun on the Spar deck is mounted on what is called the "Circular Brake Carriage." Placed longitudinally, and attached to the slide, are two heavy cogged racks of bronze.
A General Description of the Ordnance and Torpedo Outfit of the U.S.S. "Trenton" (2nd Rate)
Lieutenant Charles A. Stone