In It, Vol. 1, No. 15, February 18, 1897, by Various
we find the following news
"INVENTION AND DISCOVERY.- 1897
A New York newspaper has been making some experiments in signalling ships at night, which, if as successful as it is claimed to be, will be of the greatest service to sailors for all time to come.
Ships have a regular way of talking to one another, by means of flags arranged in certain ways...
There has been one difficulty with the flag-signals, and that has been that they were useless at night. When it became too dark for the flags to be seen, sailors had no other means of communication.
The New York paper claims to have overcome this difficulty.
In saying that ships have no means of communicating with each other, it must not be forgotten that they can use lights and send certain messages with them. But the flag system enables them to say exactly what they wish to, while through the lights they can only show where they are, and call for help in case of accident.
The invention of the searchlight set men thinking, and at last the idea struck one man that if the searchlight were turned on the flags, it ought to be perfectly possible to see them in the darkest night.
A few nights ago two tugs went down to Sandy Hook to try if the experiment would work. To their great delight they found it did answer perfectly. The tugs were stationed about a mile and a half apart, and could read with ease the messages waved across the water.
More experiments will be made, and if on further trial the method is found to be practical, a great advance will have been made in navigation...
This invention is in the nature of a powerful foghorn. It is, however, made somewhat like a musical instrument, so that different tones can be produced by it; and the idea is to have these tones arranged into a signalling code, after the fashion of the flag-signals, so that a conversation can be kept up in a similar way to that done with flags. G.H.R."
Edison's searchlight cart, from the Smitsonian: http://americanhistory.si.edu/edison/ed_d21.htm
Of course, the use of the Morse Code is better. But we have to wait till the Aldis Lamp.
According to the Oxford Dictionary: Aldis lamp, a handheld lamp for signalling in Morse code. Origin:
First World War: named after Arthur C. W. Aldis (1878–1953), its British inventor
The Aldis Lamp is a signal lamp, a visual signaling device for optical communication (typically using Morse code). Modern signal lamps are a focused lamp which can produce a pulse of light.