612 KANSAS CITY REVIEW OF SCIENCE. 
tion of a moderate quantity of air, by effecting the combustion of the superfluous 
particles of carbon, causes a higher degree of heat, and consequently a more 
lively incandescence and illumination of the still remaining particles. From this 
it is obvious that in order to obtain the highest illuminating power of a flame in 
which hydrocarbonaceous compounds are undergoing combustion, the regulation 
of the supply of air is essential. The more perfect combustion is also essential to 
the maintenance of the purity of the air of the room. In a hygienic aspect it is 
also essential that the compounds used to produce hght should be as pure as pos- 
sible, and during the last twenty years vast improvements have taken place in 
the methods of purifying gas, so that now the London gas is almost entirely free 
from sulphur and its compounds. 
We will now proceed to consider in what way candles, oil lamps and gas, as 
sources of artificial light, affect the air of a room. The effect caused on the air 
of a room by combustion is, first, to diminish the oxygen, and, secondly, to in- 
crease the carbonic acid and produce water and ammonia. If the combustion is 
imperfect the effect is also to create carbonic oxide and soot, as well as to dis- 
perse into the room any impurities which the material which is used for illumina- 
tion contains, besides the carbon and hydrogen which are necessary for purposes 
of illumination. If we look back at the graduations of improvements which have 
taken place in artificial lighting, we find that each successive step has been of ad- 
vantage to the purity of air. Probably the earliest known means of lighting was 
the torch, cut from pitch-pine, and sticky with exuded rosin. It gave a large red 
flame, and volumes of smoke which condensed into small particles of soot, collo- 
quially termed '' blacks," which adhere to faces and clothes with surprising deter- 
mination, and may give some idea of the eminent discomfort experienced in a hall 
lighted, like the Walhalla, with pine splinters. Substituting a rope for a splinter, 
and saturating this with pitch or rosin, we have the link that still, in foggy 
weather connects us with the past. 
The lamp of the type found in Pompeii probably succeeded these cruder 
means of lighting. The wick of oakum, or flax, or cotton, dipped in oil or 
bitumen, gave a smoky flame, because no effort was made to bring a sufficient 
current of air to the wick to assist the combustion. These lamps were often fed 
with scented oils, which are said to have rendered the air heavy with their per- 
fumes, which shows that they gave out a considerable amount of impurity. You 
may imagine the state of a room the morning after a symposium, when, perhaps, 
a dozen lamps had been burning for six hours, smoking fearfully, without the 
least appliance for the escape of the heavy carbonaceous fumes. Indeed, it was 
one slave's recognized duty to go round in the morning wiping the sooty pictures 
and statues. The Argand burner with its chimney, and the air brought so as to 
increase the combustion of oil lamps, was a great step in advance, and effected a 
most marked improvement in the purity of the air of a room. 
Candles with a wick made of the pith of rushes covered with wax or tallow 
are mentioned by Martial and Juvenal. These must have resembled the smoky 
rush-light of our more immediate ancestors, and the tallow candles which many 
