242 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
penitent of a lighted candle. Both life and love are symbolized as 
flame, and the fire on the hearth and the light in the window are 
synonymous with home. 
There is thus little cause to wonder that centuries ago the fire wor- 
shippers from India and elsewhere in the East journeyed to Baku 
and there built temples where hydrocarbon gases issued from the 
ground. The ruins of the temples in which their priests tended the 
eternal flames exist to our own times. 
When air is passed upward through a deep bed of incandescent 
coke as in the manufacture of producer gas, or when an automobile 
is running on too rich a mixture, or otherwise when the supply of air 
is insufficient for complete combustion, carbon monoxide is formed. 
It is utilized in metallurgy as a reducing or smelting agent of the 
utmost value and constitutes a large proportion of the important 
fuel, water gas, made by blowing steam through red-hot coke. Like 
carbon dioxide, the product of the complete combustion of carbon, it is 
a colorless and odorless gas, but, unlike the dioxide, it is intensely 
poisonous. It combines with the hemoglobin of the blood, thereby 
checking the absorption of oxygen in the lungs, and death is due to 
asphyxia from want of oxygen. The affinity of hemoglobin for car- 
bon monoxide is three hundred times that which it has for oxygen, 
and one volume of the monoxide in eight hundred of air is fatal in 
30 minutes. Much higher concentrations may be more quickly 
reached when an automobile engine is running in a closed garage. 
Carbon dioxide, the gas once brilliant in the sparkle of champagne 
and now more dully effervescent in vanilla sodas, plays a part of ex- 
traordinary interest and importance in the economy of nature. It 
is poured into the atmosphere in vast quantities from volcanoes and 
in great amounts from burning coal and forest fires. It is also 
formed by oxidation of organic matter in the soil, and according to 
Geoffrey Martin, one acre of good garden land in summer evolves 
more than 6 tons of carbon dioxide. As Faraday first showed, the 
gas is readily reduced by cold and pressure to the liquid form, and by 
rapid evaporation of the liquid it may be converted into a snowlike 
solid, the “ dry ice” now sometimes displayed in restaurateurs’ win- 
dows beside a discouraged thermometer. It is produced industrially, 
for liquefaction and distribution, from flue gases; by the burning of 
limestone, and as a by-product of alcoholic fermentations. 
Animals exhale carbon dioxide as the result of the oxidation in 
the lungs of organic wastes in the blood stream. It is normally 
present to the extent of about 4.5 per cent in human breath, and in 
a long life a man may exhale more than 20 tons of the gas. For the 
conduct of the processes which result in its production nature pro- 
vides the average man with a lung area of about 100 square yards, 
