Artificial Light | Page 7

certain stones were struck together. In the stone age, when human beings spent much of their time chiseling implements and utensils from stone by means of tools of the same substance, it appears certain that this means of producing fire was ever apparent. Many of their sharp implements, such as knives and arrow-heads, were made of quartz and similar material and it is likely that the use of two pieces of quartz for producing a spark originated in those remote periods. Alaskan and Aleutian tribes are known to have employed two pieces of quartz covered with native sulphur. When these were struck together with skill, excellent sparks were obtained.
Later, when iron and steel became available, the more modern tinder-box was developed. An early application of the flint-and-steel principle was made by certain Esquimo tribes who obtained fire by striking a piece of quartz against a piece of iron pyrites. The latter is a yellow sulphide of iron, of crystalline form, best known as "fool's gold." Doubtless, the more primitive beings used dried grass, leaves, and moss as inflammable material upon which the sparks were showered. In later centuries the tinder-box was filled with charred grass, linen, and paper. There was a long interval between the development of fire-sticks and that of the tinder-box as measured by the progress of civilization. During recent centuries ordinary brown paper soaked in saltpeter and dried was utilized satisfactorily as an inflammable material. Such devices have been employed in past ages in widely separated regions of the earth. Elaborate specimens of tinder-boxes from Jamaica, Japan, China, Europe, and various other countries are now reposing in the collections in the possession of museums and of individuals.
If the radiant energy from the sun is sufficiently concentrated upon inflammable material, the latter will ignite. Such concentration may be achieved by means of a convex lens or a concave mirror. This method of producing fire does not antedate the more primitive methods such as striking quartz or rubbing wooden sticks, because the materials required are not readily found or prepared, but it is of very remote origin. Aristophanes in his comedy "The Clouds," which is a satire aimed at the science and philosophy of his period (488-385 B. C.), mentions the "burning lens." Nearly every one is familiar with an achievement attributed to Archimedes in which he destroyed the ships at Syracuse by focusing the image of the sun upon them by means of a concave mirror. The ancient Egyptians were proficient in the art of glass-making, so it is likely that the "burning-glass" was employed by them. Even a crude lens of glass will focus an image of the sun sufficiently well to cause inflammable material to ignite.
The energy in sunlight varies enormously, even on clear days, because the water-vapor in the atmosphere absorbs some of the radiant energy emitted by the sun. This absorbed radiation is chiefly known as infra-red energy, which does not arouse the sensation of light. When the water-vapor content of the atmosphere is high, the sun, though it may appear as bright to the eye, in reality is not as hot as it would be if the water-vapor were not present. However, a fire may be kindled by concentrating only the visible rays in sunlight because of the enormous intensity of sunlight. A convex lens fashioned from ice by means of a sharp-edged stone and finally shaped by melting the surfaces as they are rubbed in the palms of the hands, will kindle a fire in highly inflammable material if the sun is high and the atmosphere is fairly clear. Burning-glasses are used to a considerable extent at the present time in certain countries and it is reported that British soldiers were supplied with them during the Boer War. Indicative of the predominant use to which the glass lens was applied in the past is the employment of the term "burning-glass" instead of lens in the scientific writings as late as a century or two ago.
As civilization advanced, leading intellects began to inquire into the mysteries of nature and the periods of pure philosophy gave way to an era of methodical research. Alchemy and superstition began to retire before the attacks of those pioneers who had the temerity to believe that the scheme of creation involved a vast network of invariable laws. In this manner the powerful sciences of physics and chemistry were born a few centuries ago. Among other things the production of fire and light received attention and the "dark ages" were doomed to end. The crude, uncertain, and inconvenient methods of making fire were replaced by steadily improving scientific devices.
Matches were at first cumbersome, dangerous, and expensive, but these gradually evolved into the safety matches of the present time. Although they were primarily intended for lighting fires and various kinds