16 Economical Stemn 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 economical use of fuel for 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 1 jth atmosphere, filling the cylinder, consumes fuel, 

 say as 1, eiFect 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 engine, 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 inside 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 I 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 marmer o^ preventing exj)losions ; 

 the manner of supply, by throwing in water when the engine is not 



