the efficiency of light-production. Some figures of the
Census Bureau may be of interest. These are given for 1914 in order that
the abnormal conditions due to the recent war may be avoided. The
figures pertaining to the manufacture of gas for sale which do not
include private plants are as follows for the year 1914 for this
country:

Number of establishments 1,284
Capital $1,252,421,584
Value of products (gas, coke, tar, etc.) $220,237,790
Cost of materials $76,779,288
Value added by manufacture $143,458,502
Value of gas $175,065,920
Coal used (tons) 6,116,672
Coke used (tons) 964,851
Oil used (gallons) 715,418,623
Length of gas mains (miles) 58,727
Manufactured products sold
Total gas (cubic feet) 203,639,260,000
Straight coal gas (cubic feet) 10,509,946,000
Carbureted water gas (cubic feet) 90,017,725,000
Mixed coal- and water-gas (cubic feet) 86,281,339,000
Oil gas (cubic feet) 16,512,274,000
Acetylene (cubic feet) 136,564,000
Other gas, chiefly gasolene (cubic feet) 181,412,000
Coke (bushels) 114,091,753
Tar (gallons) 125,938,607
Ammonia liquors (gallons) 50,737,762
Ammonia, sulphate (pounds) 6,216,618

Of course, only a small fraction of the total gas manufactured is used
for lighting.

According to the U. S. Geological Survey, the quantities of gas sold in
this country in the year 1917 were as follows:

Coal-gas 42,927,728,000 cubic feet
Water-gas 153,457,318,000 " "
Oil-gas 14,739,508,000 " "
Byproduct gas 131,026,575,000 " "
Natural gas 795,110,376,000 " "

In 1914 there were 38,705,496 barrels (each fifty gallons) of
illuminating oils refined in this country and the value was $96,806,452.
About half of this quantity was exported. In 1914 the value of all
candles manufactured in this country was about $2,000,000, which was
about half that of the candles manufactured in 1909 and in 1904. In 1914
the value of the mat