I have made a makeshift arrangement on the principle of my heliostat, using the object glass of an opera-glass for the lens, and an ordinary looking-glass: the great size and short focus of the object glass is a great convenience when using a mirror with a wide frame.
Professor W. H. Miller, the Foreign Secretary of the Royal Society, has since invented a yet more compact method of directing the flash, which he has described in the Proceedings of the Royal Society for 1865. It consists of a plate of silvered glass, one of whose rectangular corners is accurately ground and polished. On looking into the corner when the glass is properly held an image of the sun is seen, which overlays the actual flash. Beautifully simple as this instrument is, I do not like it so much as my own, for the very fact of its requiring no "setting" is its drawback. With mine, when the image of the sun is lost it is immediately found again by simply rotating the instrument on its axis; but with Professor Miller's the image must be felt for wholly anew.
Fire Signals.--Fire-beacons, hanging up a lantern, or setting fire to an old nest high up in a tree, serve as night-signals; but they are never to be depended on without previous concert, as bushes and undulations of the ground will often hide them entirely. The sparks from a well-struck flint and steel can be seen for much more than a mile.
Smoke Signals.--The smoke of fires is seen very far by day; and green wood and rotten wood make the most smoke. It is best to make two fires 100 yards apart, lest your signalling should be mistaken for an ordinary fire in the bush. These double fires are a very common signal to vessels in the offing, on the African coast.
Other Signals.--By Sight.--A common signal for a distant scout is, that he should ride or walk round and round in a circle from right to left, or else in one from left to right.
Mr. Parkyns, speaking of Abyssinia, describes the habits of a caste of robbers in the following words:--"At other times they will lie concealed near a road, with scouts in every direction on the look-out; yet no one venturing to speak, but only making known by signs what he may have to communicate to his companions or leader. Thus he will point to his ear and foot on hearing footsteps, to his eyes on seeing persons approach, or to his tongue if voices be audible; and will also indicate on his fingers the numbers of those coming, describing also many particulars as to how many porters, beasts of burden or for riding, there may be with the party."