A few remarks on this method of obtaining light from the combustion
of crude petroleum may be added, as the light has been put forward
as a cheaper and better substitute for the electric arc. The Lucigen
light is produced by burning creosote oil, tar oil, or other heavy
hydro-carbons, by means of compressed air in a special form of lamp,
and consists of a cylinder at the side of which a steam donkey
compressing pump is mounted, or in a more recent form known as the
Wells’ light, no separate air compressor is used, but, instead, the
pressure is obtained from the water mains or from a small force pump.
The cost is stated to be 3_d._ per hour for 2,500 candle-power,
requiring three gallons of oil per hour, but is in reality at the
present time double this owing to the price of the oil, which, under
the most advantageous circumstances, costs on average 2_d._ per
gallon. At the Forth Bridge these lights have been found of use in
illuminating open spaces, but have not supplanted the electric arc
lights which are universally employed for the lighting of the works and
the interior of the shops. The disadvantages are the noise, the oil
shower which pervades the vicinity of the light causing timber staging
to be highly inflammable, and the difficulty of preventing water from
entering the burner, a few drops sufficing to extinguish the light.
The use of the Lucigen light is, therefore, very limited, and it is
probable that, in situations where shadows from the arc light are found
to be objectionable, large incandescent electric lamps, which are
supplied up to 1,500 candle-power, would meet the case; or, failing
these, petroleum could be burnt in lamps similar to those used in
lighthouses with greater safety, and at not much increased cost, than
the compressed-air system.