; the Circumference 33 feet. The whole
Construction of the Lanthorn is Iron; the Top covered with
Copper. There are 48 Oil Blazes. The Building from the Surface
is Nine Stories; the whole from Bottom to Top is 103 Feet.

From these early years the number of lighthouses has steadily grown,
until now the United States maintains lights along 50,000 miles of
coast-line and river channels, a distance equal to twice the
circumference of the earth. It maintains at the present time about
15,000 aids to navigation at an annual cost of about $5,000,000. In 1916
this country was operating 1706 major lights, 53 light-ships, and 512
light-buoys--a total of 5323.

The earliest lighthouses were equipped with braziers or grates in which
coal or wood was burned. These crude light-sources were used until after
the advent of the nineteenth century and in one case until 1846. In the
famous Eddystone tower off Plymouth, England, candles were used for the
first time. The first Eddystone tower was completed in 1698, but it was
swept away in 1703. Another was built and destroyed by fire in 1755.
Smeaton then built another in 1759. Inasmuch as Smeaton is credited with
having introduced the use of candles, this must have occurred in the
eighteenth century; still it appears that, as we have said, the Boston
Light, built in 1716, used oil-lamps from its beginning. However,
Smeaton installed twenty-four candles of rather large size each credited
with an intensity of 2.8 candles. The total luminous intensity of the
light-source in this tower was about 67 candles. Inasmuch as this was
before the use of efficient reflectors and lenses, it is obvious that
the early lighthouses were rather feeble beacons.

According to British records, oil-lamps with flat wicks were first used
in the Liverpool lighthouses in 1763. The Argand lamp, introduced in
about 1784, became widely used. The better combustion obtained with this
lamp having a cylindrical wick and a glass chimney greatly increased the
luminous intensity and general satisfactoriness of the oil-lamp. Later
Lange added an improvement by providing a contraction toward the upper
part of the chimney. Rumford and also Fresnel devised multiple-wick
burners, thus increasing the luminous intensity. In these early lamps
sperm-oil and colza-oil were burned and they continued to be until the
middle of the nineteenth century. Cocoanut-oil, lard-oil, and olive-oil
have also been used in lighthouses