To obtain Fire from the Sun.--Burning-glasses.--The object-glass, and every other convex glass of a telescope is a burning-glass, and has only to be unscrewed to be fit for use. The object lenses of an opera-glass are very efficient. The larger the glass and the shorter its focus, the greater is its heating power. Convex spectacle glasses and eye glasses are too small and of too long a focus to be used with effect, except when the sun is very hot. An old-fashioned watch-glass, filled with water, and having the rays of a powerful sun glittered down upon it vertically by help of a mirror, will give a light. Dr. Kane and other arctic travellers have made burning-glasses of ice.
Reflectors.--The inside of the polished metal cover of a hunting-watch will sometimes converge a sufficiency of rays, to burn. The vestal fire of Rome and the sacred fire of the Mexicans were obtained by means of reflectors. If I understand aright, they consisted of a stone with a conical hollow, carefully polished, the apex of the hollow cone was a right angle: the tinder was held in the axis of the cone. See Tylor's 'Early History of Mankind.'
Black Tinder.--Tinder that is black by previous charring, or from any other cause, ignites in the sun far sooner than light-coloured tinder.
Fire by conversion of motion into heat.--General Remarks.--When a moving body is arrested, heat is given out; the quantity of heat being in exact proportion to the mass, multiplied into the square of its velocity. Thus if a cannon ball be fired at an iron target, both it and the ball become exceedingly hot. There is even a flash of light when the velocity of the ball is very high. When bullets are fired with heavy charges at a target, the lead is just melted by the heat of impact, and it "splashes," to use a common phrase. It is obvious from these two examples, that no velocity which the hand of man is able to give to a steel, when striking a flint, or to one stick rubbing against another stick, will be competent to afford a red-hot temperature unless the surface against which impact or friction is made be very small, or unless great care be taken to avoid the wasteful dissipation of heat. The spark made by a flint and steel, consists of a thin shaving of steel, scraped off by the flint and heated by the arrested motion. When well struck, the spark is white-hot and at that temperature it burns with bright scintillations in the air, just as iron that is merely red-hot burns in pure oxygen. This is the theory: now for the practice.
Flints.--If we may rely on a well-known passage in Virgil, concerning Æneas and his comrades, fire was sometimes made in ancient days by striking together two flints, but I confess myself wholly unable to light tinder with flints alone, and I am equally at a loss to understand what were the "dry leaves" that they are said in the same passage to have used for tinder. Neither can I obtain fire except with a flint and steel, or, at least, hardened iron; a flint and ordinary iron will not give an available spark. Flints may be replaced by any siliceous stone, as agate, rock-crystal, or quartz. Agate is preferred to flint, for it gives a hotter spark: it is sold by tobacconists. A partly siliceous stone, such as granite, will answer in default of one that is wholly siliceous. I have been surprised at finding that crockery and porcelain of all kinds will make a spark, and sometimes a very good one. There are cases where a broken teacup might be the salvation of many lives in a shipwrecked party. On coral-reefs, and other coasts destitute of flinty stones, search should be made for drift-wood and drifted sea-weed. In the roots of these, the pebbles of other shores are not unfrequently entangled, and flint may be found among them. The joints of bamboos occasionally contain enough silex to give a spark.
Steels.--The possession of a really good steel is a matter of great comfort in rough travel, for, as I have just said, common iron is incompetent to afford a useful spark, and hardened iron or soft steel is barely sufficient to do so. Any blacksmith will make a good steel out of an old file, if he has nothing more appropriate at hand. A substitute for a steel can be made, even by an ordinary traveller, out of common iron, by means of "casehardening" (which see). The link of a chain, or the heel of a boot, or a broken horse-shoe, is of a convenient shape for the purpose.
Pyrites are, and have been, widely used for striking sparks. Two pieces struck together, or one piece struck with a steel, gives a good spark; but it is a very friable mineral, and therefore not nearly so convenient as flint.
Guns.--If you wish to get a light by means of a flint-and-steel gun, the touch-hole may be stuffed up, and a piece of tinder put among the priming powder: a light can be obtained in that way without firing the gun. With a percussion-cap gun, a light may be obtained by putting powder and tinder outside the nipple and round the cap; it will, though not with certainty catch fire on exploding the cap. But the common way with a gun is to pour in a quarter of a charge of powder, and above it, quite loosely, a quantity of rag or tinder. On firing the gun straight up in the air, the rag will be shot out lighted; you must then run after it as it falls, and pick it quickly up. With percussion-caps, gunpowder, and tinder, and without a gun, a light may sometimes be had on an emergency, by scratching and boring with a knife, awl, or nail, at the fulminating composition in the cap, till it explodes; but a cap is a somewhat dangerous thing to meddle with, as it often flies with violence, and wounds. Crushing gunpowder with hard stones may possibly make it explode.
Lucifers.--An inexperienced hand will waste an entire boxful of them, and yet will fail in lighting a fire in the open air, on a windy day. The convenience of lucifers in obtaining a light is very great, but they have two disadvantages: they require that the air should be perfectly still, while the burning sulphur is struggling to ignite the stick; and, again, when the match is thrust among the wood, the sticks upon which is has to act, have not been previously warmed and consequently, though one or two of them may become lighted, the further progress of the fire is liable to cease. On the other hand, in methods where the traveller begins with tinder, and blows its spark into a flame, the adjacent wood becomes thoroughly heated by the process, and the flame, once started, is almost certain to maintain itself. Consequently, in lighting a fire with lucifers, be careful to shield the match from the wind, by throwing a cloak or saddle-cloth, or something else over the head, whilst you operate; and secondly, to have abundance of twigs of the smaller sizes, that there may be no uncertainty of the lucifer-match being able to light them, and set the fire a-going. In a steady downfall of rain, you may light a match for a pipe under your horse's belly. If you have paper to spare, it is a good plan to twist it into a hollow cone; to turn the cone with its apex to the wind; and immediately after rubbing the match, to hold it inside the cone. The paper will become quickly heated by the struggling flame and will burst into a miniature conflagration, too strong to be puffed out by a single blast of air. Wax lucifers are undoubtedly better than wooden ones, for in damp weather, wooden ones will hardly burn; but wax is waterproof, and independent of wet or dry. When there is nothing dry, at hand, to rub the lucifer-match against, scratch the composition on its head with the edge of a knife or with the finger-nail. It is a sure way of lighting it; and with care, there is no need of burning the fingers.
Fire-sticks.--In every country without exception, where inquiry has been made, the method of obtaining fire by rubbing one stick against another, has been employed. In savage countries the method still remains in present use; in nearly all the more civilised ones, it has been superseded within historic periods by flints and steels and the like, and within this present generation by lucifer-matches. The only instance I know in which flints are said to have preceded fire-sticks, is in the quotation below from Pliny. A light has also been obtained in pre-historic times, as I have already mentioned, by reflecting the sun from a hollow surface; but this method required costly apparatus, and could never have been in common use. Hence, although so far as I am aware, the Bible, and Homer, and other records of great antiquity, are absolutely silent on the contemporary methods of procuring fire; and although Pliny says the reverse--I think we are justified in believing that the plan of rubbing sticks together was absolutely universal in the barbaric infancy of the human race. In later Greek History, Prometheus is accredited with the invention of fire-sticks. Among the Romans both Seneca and Pliny write about them. Pliny says (Nat. Hist. xvi. 76, 77), "There is heat in the mulberry, in the bay-laurel, in ivy, and in all plants whence fire-sticks are made. The experience of soldiers reconnoitring for encamping-grounds, and that of shepherds, made this discovery; for a stone is not always at hand whence a spark might be struck. One piece of wood therefore, is rubbed by another, and it catches fire through the friction, while a dry tindery substance--fungus and leaves are the most easilyattainable--is used to perpetuate the fire. Nothing is better than ivy used as the stick to be rubbed, and bay-laurel as the stick to rub with. Wild vine--not the 'labrusca'--is also found good."