outweighing the interest on their extra first cost. So few people appear
to have a clear idea of the vast importance of economy of fuel in mills
and factories that I perhaps cannot better conclude than by giving an
example showing the saving to be effected in a large establishment by an
economical engine.

I will take the case of a flouring mill in this city which employed two
engines that required forty pounds of water to be converted into steam
per hour per indicated horse-power. This, at the time, was considered a
moderate amount and the engines were considered "good."

These engines indicated seventy horse power each, and ran twenty-four
hours per day on an average of three hundred days each year, requiring
as per indicator diagrams forty million three hundred and twenty
thousand pounds (40 x 70 x 24 x 300 x 2 = 40,320,000) of feed water to
be evaporated per annum, which, in Philadelphia, costs three dollars
per horse-power per annum, amounting to (70 x 2 x 300 = $420.00) four
hundred and twenty dollars.

The coal consumed averaged five and one-half pounds per hour per
horse-power, which, at four dollars per ton, costs

((70 x 2 x 5.5 x 24 x 300) / 2,000) x 4.00= $11,088

Eleven thousand and eighty-eight dollars.

Cost of coal for 300 days. $11,088
Cost of water for 300 days. 420
-------
Total cost of coal and water. $11,503