47 
interval being recognisable without the aid of a glass. 
That is to say, two trained sappers, each provided with a 
mirror, can readily speak to one another, supposing the sun 
is shining, with an interval of fifty miles between them, 
provided their stations are sufficiently high and no rising 
ground intervene to stop the rays. 
“The- adjustment of the military heliograph is a very 
simple matter. An army leaves its base, where a heliograph 
station is located, and, after travelling some miles, desires 
to communicate with the stay-at-homes. A hill in the 
locality is chosen and a sapper ascends with his heliograph, 
which is simply a stand bearing a mirror swung like the 
ordinary toilet looking-glass, except that it swings horizon- 
tally. It is also pivoted so as to move vertically as well. 
Behind the mirror, in the very centre, a little quicksilver 
had been removed, so that the sapper can go behind liis 
instrument and look through a tiny hole in it towards the 
station he desires to signal. Having sighted the station, 
adjusting the mirror, he next proceeds to set up in front of 
the heliograph a rod, and upon this rod is a movable stud. 
This stud is manipulated like the foresight of a rifle, and 
the sapper again standing behind his instrument, directs the 
adjustments of this stud until the hole in the mirror, the 
stud, and the distant station, are in a line. The heliograph 
is then ready to work ; and in order to flash signals so that 
they may be seen at a distance, the sapper has only to take 
care that his mirror reflects the sunshine on the stud just in 
front of him.” 
Early in June, 1880, a writer in the Lahore Gazette called 
attention to what he regards as an early instance of helio- 
graphic signalling. He says : — 
“ But there is a still older instance of the use of the helio- 
graph indicated in a ballad as old as 1511, viz., the story of 
the fight between the Great Harry and its consort under 
Lord Howard, on the one side, and the Lion and the Union 
