As Marconi Sahib says tis the Aldis lamp, the big mounted 10in,20in and 40in are called signal projectors and do double duty as searchlights.
And the reason taint used much no more!
The Lay Of The Last Signalman
On a thickly wooden sponson where the last projector stands,
The museum pair of hand flags hanging idly in my hands,
with my jargon half forgotten of my stock and trade bereft,
I wonder what's ahead of me - the only bunting left.
The relics of my ancient craft have vanished one by one.
The Cruisers arch, the Morse flag and manoeuvring lights have gone,
And I hear they'd be as useless in the final Global war
As the helio, the foghorn and the masthead semaphore.
The masthead is sprouting gadgets like a nightmare Christmas tree.
There are whips and stubs and wave guides where my halyards used to be,
and I couldn't hoist a tack line through that lunatic array,
for at every height and angle there's a dipole in the way.
The alert and hawk-eyed Signalman is rendered obsolete
by the electrically operated optics of the fancy modern Fleet.
And the leaping barracuda or the charging submarine
can be spotted as a blob upon fluorescent screen.
To delete the human error, to erase a noble breed,
we rely upon a relay and we pin our faith to creed.
So we press a button, make a switch and spin a wheel,
and it's cent percent efficient when we're on an even keel.
But again I may be needed, for the time will surely come,
when we have to talk in silence and the modern stuff is dumb.
When the signal lantern's flashing or the flags are flying free -
it was good enough for Nelson and it's good enough for me.
