8 24 8,700
1860 3 11 33 12,000
1870 3 22 66 24,000
1880 3.5 36 126 46,000
1890 4 50 200 73,000
1900 5 154 770 280,000

It is seen from the foregoing that in a century the candle-equivalent
obtainable for the same cost to the householder increased at least
thirty times, while the hours during which this light is used have
nearly doubled. In other words, in the nineteenth century the
candle-hours obtainable for $20.00 per year increased about fifty
times. Stated in another manner, the cost of light at the end of the
century was about one fiftieth that of candle light at the beginning of
the century. One authority in computing the expense of lighting to the
householder in a large city of this country has stated that

coincident with an increase of 1700 per cent. in the amount of
night lighting of an American family, in average circumstances,
using gas for light, there has come a reduction in the cost of
the year's lighting of 34 per cent. or approximately $7.50 per
year; and that the cost of lighting per unit of light--the
candle-hour--is now but 2.8 per cent. of what it was in the
first half of the nineteenth century. No other necessity of
household use has been so cheapened and improved during the
last century.

In general, the light-user has taken advantage of the decrease by
increasing the amount of light used and the period during which it is
used. In this manner the greatly diminished cost of light has been a
marked sociological and economic influence.

After Murdock made his first installation of gas-lighting in an
industrial plant early in the nineteenth century, he published a
comparison of the expense of operation with that of candle-lighting. He
arrived at the costs of light equivalent to 1000 candle-hours as
follows:

1000 candle-hours
Gas-lighting at a rate of two hours per day $1.95
" " " " " three " " " 1.40
Candle-lighting 6.50

It is seen that the longer hours of burning reduce the cost of
gas-lighting by reducing the percentage of overhead charges. There are
no such fac