| 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 matches manufactured in this country was $12,556,000. This has increased steadily from $429,000 in 1849. In 1914 the glass industries in this country made 7,000,000 lamps, 70,000,000 chimneys, 16,300,000 lantern globes, 24,000,000 shades, globes, and other gas goods. Many millions of other lighting accessories were made, but unfortunately they are not classified.
Some figures pertaining to public electric light and power stations of the United States for the years 1907 and 1917 are as follows:
In general, there is a large increase in the various items during the decade represented. The output of the central stations doubled in the five years from 1907 to 1912, and doubled again in the next five years from 1912 to 1917. Street lamps were not reported in 1907, but in 1912 there were 348,643 arc-lamps served by the public companies. The number of arc-lamps decreased to 256,838 in 1917. On the other hand, there were 681,957 electric filament street lamps served in 1912, which doubled in number to 1,389,382 in 1917. The cost of construction and equipment of these central stations totaled more than $3,000,000,000 in 1917.
Although there is no immediate prospect of the failure of the coal and oil supplies, exhaustion is surely approaching. And as the supplies of fuel for the production of gas and electricity diminish, the cost of lighting may advance. The total amount of oil available in the known oil-fields of this country at the present time has been estimated by various experts between 5,000,000,000 and 20,000,000,000 barrels, the best estimate being about 7,000,000,000. The annual consumption is now about 400,000,000 barrels. These figures do not take into account the oil which may be distilled from the rich shale deposits. Apparently this source will yield a hundred billion barrels of oil. In a similar manner the coal-supply is diminishing and the consumption is increasing. In 1918 more than a half-billion tons of coal were shipped from the mines. The production of natural gas perhaps has reached its peak, and, owing to its relation to the coal and oil deposits, its supply is limited.
Although only a fraction of the total production of gas, oil, and coal is used in lighting, the limited supply of these products emphasizes the desirability of developing the enormous water-power resources of this country. The present generation will not be hard pressed by the diminution of the supply of gas, oil, and coal, but it can profit by encouraging and even demanding the development of water-power. Furthermore, it is an obligation to succeeding generations to harness the rivers and even the tides and waves in order that the other resources will be conserved as long as possible. Science will continue to produce more efficient light-sources, but the cost of light finally is dependent upon the cost of the energy supplied to these lamps. At the present time water-power is the anchor to the windward.