WORKING MODEL OF STEAM-ENtilNR. 



385 



In cardboard case, price $2.50 ; cedar case, $3.50 ; 

 mahogany case, French polished, with lock and key, 

 $5.00. Larger cases of chemicals and apparatus at 

 $10, $15, $20, and $28. 



Fig. 801. 



fcV- ig> 



Working Model of Bt cam-Engine. (Fig. 801.) The 

 above represents a neat and compact model of this in- 

 teresting machine, sometimes called the "king of ma- 

 chines," and as an example of a self-regulator is unsur- 

 passed by any other forms of machinery. The boiler for 

 the generation of steam is of strong copper or brass, and 

 is heated by the flame of a spirit-lamp, having a number 

 of wicks. On the top of the boiler is placed the safety- 

 valve, with its lever and weight; this valve opens upward, 

 so that should the elastic force of the steam become too 

 great, the valve opens and the steam escapes. At one 

 end of the boiler is a water-cock, and at the other end, 

 and near the top, a cock and the steam-pipe. This 

 stearn-pipe connects with the cylinder of the engine, for- 

 cing a steam-tight piston backward and forward by an 

 arrangement of sliding valves, so adjusted as alternately 

 to admit the steam above and below the piston, and also 

 alternately to let it escape in the air. The working 

 beam is supported at its fulcrum by a neat and substan- 



