re 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 of
lamps, billions of them are now used yearly as convenient light-sources.
Smoldering hemp or other material treated with niter and other
substances was an early form of match used especially for discharging
firearms. The modern wax-taper is an evolutionary form of this type of
light-source.

Phosphorus has long played a dominant role in the preparation of
matches. The first attempt at making them in their modern form appears
to have occurred about 1680. Small pieces of phosphorus were used in
connection with small splints of wood dipped in sulphur. This type of
match did not come into general use until after the beginning of the
nineteenth century, owing to its danger and expense. White or yellow
phosphorus is a deadly poison; therefore the progress of the phosphorus
match was inhibited until the discovery o