610 KANSAS CITY REVIEW OF SCIENCE. 
PROGRESS IN ARTIFICIAL LIGHTING. 
The vast improvements which have taken place in the production of artifi- 
cial hght in recent years — improvements which bear to a considerable extent 
upon the hygienic aspect of the question — make it especially desirable to bring 
the subject before the public. The introduction of the electric light has had the 
result of stimulating invention in gas lighting, and there have been recently in- 
troduced new methods of gas lighting which bid fair to retard the introduction 
of the electric light for domestic use. Every form of matter when sufficiently 
heated has the power of emitting rays of light, and thus becomes self-luminous. 
This condition is termed incandescent, and the self-luminous worlds, as the 
Sun and fixed stars, are, doubtless, in a condition of intense incandescence. 
All artificial sources of Hght depend upon the development of light during 
incandescence. For the illumination of our streets and houses at night we have 
hitherto made use of a combustible gaseous combination of carbon and hydro- 
gen, which forms the chief constituent of ordinary coal gas. When this hydro- 
carbon burns — that is to say, when its elements unite with the oxygen of the air 
— it undergoes partial decomposition and evolves heat. Carbon is separated in 
the solid state, and floats, in a finely divided and incandescent state, in the 
interior of the burning vapor, and this constitutes the flame. The presence of 
these particles of carbon may be easily shown by holding any non-combustible 
body in the flame, when the carbon in fine powder will be deposited upon it, 
forming a layer of soot. The combustion of the particles of carbon takes place 
at the border of the flame, where they are first brought into contact with the 
oxygen of the air, but if the supply of oxygen to them be insufficient in quantity, 
they escape in a partially unburned condition in the form of a dark cloud, and 
the flame is said to smoke. The brightness of the flame is owing to these solid 
incandescent particles, for the burning gas itself possesses only a feeble illumi- 
nating power. It would, moreover, appear that the luminosity of a flame is 
due to the heat of the flame, and Dr. Frankland has shown us that hydrogen or 
carbon monoxide, when burned with oxygen under a pressure of from 15 to 20 
atmospheres, yields a luminous flame. 
No doubt the Bunsen burner gives a smokeless and non-luminous flame, 
although it cannot be said that the flame of the Bunsen burner is in any sense 
less hot than a luminous gas-flame. In the Bunsen burner ordinary gas con- 
ducted through India-rubber tubing streams into the tube of the burner. Air 
enters, however, through two openings, and mixes itself with the gas in the 
interior of the tube. If the mixture issuing from the tube be ignited, it burns 
with an extremely feeble flame, which deposits no soot on bodies held in it, for 
new oxygen is admitted not only to the border of the flame, but throughout its 
whole mass, and the carbon is accordingly burned into carbonic acid before it 
can separate in the solid form, so that the flame is composed of incandescent 
