16 Economical Steam Boats. 
The least costly engines are those which are placed horizontally, 
and use steam of high temperature and great force. ‘They are much 
employed on the Mississippi. ‘There is one in a new boat on the 
- Hudson, made at Pittsburg. It is represented in Mr. Renwick’s 
Treatise, page 6 
But the most sie asiecad use of fuel fai steam, is where the engine 
works it expansively, using a condenser. ‘To this subject a chapter 
of that work is well devoted : at page 73, a table of effects shows 
that steam of 1th atmosphere, filling the cylinder, consumes fuel, 
say as 1, effect 10, while 4 atmospheres, using {th cylinder full, con- 
sumes half as much fuel, and the effect is 20, or double. To raise 
the steam from 1 atmosphere to 4, requires an increase of tempera- 
ture of only 45°, that is, from 212° to 291°. This shows the ad- 
vantage of using even with a condensing enging, boilers that will 
safely bear 4 atmospheres. 
The form of boiler, for this and for other reasons, which I have 
supposed. the most economical, is calculated to use anthracite coal, 
and do without aside flues. 
It consists of four single cylinders, placed side by side, the two 
middle ones a little asunder, to allow the coal to fall from hoppers 
over this space on to a sharp ridge, which causes it to slide down to 
two long narrow grates under the middle boilers. ‘The draft is 
thence sidewise under the outer ones, rising over a ridge to impinge 
on their bottom before it turns down under them to reach the vents 
on the other side; which are small funnels leading to the main fun- 
_ nel above. 
This method allows the coal to burn near the bottom of the boil- 
ers, and advantageously as the course of the draft does not intercept 
the heat. 
The carburetted hydrogen gas fire, as an auxiliary for flame, is 
very conveniently applied to this form of boiler ; when if it be found 
to require more surface to act on, the number of cylinders might be 
six, instead of four: and three, (half this arrangement,) may be con- 
veniently employed in some instances. 
Thus [ have endeavored to present in one view the most econom- 
ical hull; the manner of working an engine with most effect of 
steam; the manner of making a boiler to use at once the most com- 
pact, cheap and active fuel; the manner of preventing explosions; 
manner of supply, by throwing in water when the engine is not 
