No.4 Battery

No.4 Battery was one of the heavy batteries built on the lower level of Fort Carlisle.  Armed with four 11-inch RML guns mounted behind armoured shields and in iron casemates, it was also one of the best protected. Very similar to the Right Lower Battery at Fort Camden built at the same time.

In about 1900, when the Upper Level Batteries were be upgraded,  the armoured casemates were converted to an electrical power station.  These generators were primarily to power the defence electric lights covering the minefield and Brennan Torpedo beaten zone.

The iron casemates at Number 4 Battery, Fort Carlisle were converted to be an engine room in about 1900.  Inside this engine room there is an old switchboard which is fairly unique in that it has largely survived over the years.

The images show the electrical switchboard (electrical control panel) inside Number 4 Battery. The heavy black backing panels are likely made of slate. Looking at the damage on the top left, this looks more like slate than any Bakelite resin.  Slate was used in early electrical engineering because it is naturally fireproof and acts as an excellent electrical insulator.

The round gauges at the top are analog voltmeters or ammeters used to monitor the electrical load. Made by Johnson & Phillips Ltd. of London, a prominent British electrical engineering firm founded in 1875 that specialized in switchgear and heavy power distribution. The curved display (scale) shows a range from 0 to 250 Amperes, indicating they monitored heavy-duty industrial or military power loads.

The long metal levers with handles, called knife switches. These were manual switches used to physically connect or disconnect high-voltage circuits.  Ammeters placed above the switches to monitor the current.  These carried an extreme risk of electric shock and electrical arcs risked burns and fire.

The “Direct” and “Indirect” Labels likely refer to the type of lighting or power distribution. “Direct” might have been for essential circuits or primary DC (Direct Current) lines, while “Indirect” could refer to secondary lighting systems or AC (Alternating Current) circuits converted via a transformer.

The bulky, rusted boxes at the bottom are heavy-duty fuse holders or circuit breakers designed to protect the equipment from power surges.  These boxes appear to have been made by either Bill Switchgear or Midland Electric Manufacturing (MEM).  These are double-pole switchfuses. They are designed to house “rewireable” ceramic fuses inside a heavy, protective cast iron shell to prevent sparks or fire from escaping if a fuse “blows”. The circular knob is a threaded locking screw that holds the front cover shut. It must be unscrewed to access the fuses inside.

The two gauges at the very top of the central panels (one missing, one present) likely served as main monitoring instruments for the entire board.  These appear to be ammeter or ampere meter designed for heavy duty industrial monitoring.  They measured electric flow.

The four items mounted on the wooden beam behind the switchboard are ceramic (porcelain) insulators.  These served as wire holders or “cleats” to securely anchor heavy electrical cables while keeping them physically separated from the wall and each other.