The combined effect of decreasing cost of fuel or electrical energy for light-sources and of the great improvements in light-production gave to the householder, for example, a constantly increasing amount of light for the same expenditure. For example, the family which a century ago spent two or three hours in the light of a single candle now enjoys many times more light in the same room for the same price. It is interesting to trace the influence of this greatly diminishing cost of light in the home. For the sake of simplicity the light of a candle will be retained as the unit and the cost of light for the home will be considered to remain approximately the same throughout the period to be considered. In fact, the amount of money that an average householder spends for lighting has remained fairly constant throughout the past century, but he has enjoyed a longer period of artificial light and a greater amount of light as the years advanced. The following is a table of approximate values which shows the lighting obtainable for $20.00 per year throughout the past century exclusive of electricity: Hours Equivalent of Candle-hours Year per night light in candles per night per year 1800 3 5 15 5,500 1850 3 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.