Trow Rock Floating Platform

Trow Rock Floating Platform is a late 19th-century structure built in 1887 for the Inspector General of Fortifications to test a Clarke Maxim Disappearing Platform designed for a 6-inch breech-loading gun. The platform is made of mass concrete and has a cylindrical shape with an internal diameter of approximately 21 feet, featuring a west extension for an approach tunnel. The exterior is rough-shuttered, while the interior displays runners for a steel floating platform that has since been removed, along with the entrance to the tunnel. The structure is set deep into the ground to allow for the water on which the platform could rise and fall, operated by air pressure pumps, but it is now mostly filled with earth.

Historically, trials of the platform were conducted on December 15th and 16th, 1887, but the raising and lowering mechanism was deemed too slow, leading to the abandonment of this system in favor of the quicker and cheaper Elswick hydro-pneumatic mounting. The platform is of historical interest as a relic of late 19th-century artillery development experiments.