Chapter II: Part I

PRODUCTION OF ARTIFICIAL LIGHT, &c. 8.

Production of the flame generated during the combustion of certain
bodies.--Characters of flame when perfect.--Most luminous flame, how
produced with the least consumption of combustible matter.--Conditions
necessary for that purpose.--Importance of this subject, with regard
to the production and supply of artificial light.--The flame of bodies
may be tinged.--Blue flame, red flame, green flame, &c.--Opinion
concerning the origin of light emitted by bodies burning with flame.--
Philosophy of the subject.--Theory of the action of the instruments of
illumination.--Rude method of procuring light employed in some
countries.--Chemical action of candles, and lamps.--Agency of the
tallow, oil, &c.--Office of the wick.--Reason why tallow candles
require snuffing, and wax candles snuff themselves--Further
observations on the subject.

METHOD OF ASCERTAINING THE ILLUMINATING POWER OF CANDLES, LAMPS, AND
OTHER LUMINOUS BODIES. 22.

Optical principle assumed as law for determining the relative strength
of lights of different kinds.--Admeasurement of the intensities of
light.--Quantity of wax, tallow, oil, &c. requisite for producing a
light of a certain strength.--Method of increasing the light of tallow
candles, and to obviate the necessity of snuffing them.--A tallow
candle placed in an inclined position gives more light than when
placed perpendicularly and snuffed with an instrument.--Explanation of
the fact.--Further observations on this subject.--Comparative cost of
the light obtained by burning tallow candles of different sorts and
sizes.