In the case of factories the exhaust steam from the engines used for driving the working machinery is made use of and forms the most economical method of heating possible.
The system is economical in fuel, but needs skilled attendance to keep the appliances and fittings in order.
In the choice of a boiler of this description it should be remembered that rapid heating, economical combustion of fuel, and facilities for cleaning, are requisites, the absence of any of which considerably lowers the efficiency of the apparatus.
On his long, gaunt body, he carried no spare flesh, no superfluous beard, his chin having a soft, economical nap to it, like the worn nap of his broad-brimmed hat.
For God's sake, be economical with your lamps and candles! not a gallon you burn, but at least one drop of man's blood was spilled for it.