DOMINION OVER PHYSICAL NATURE 



465 



Fig. 5. — Operation of boring cylinder. A is the 

 boring bar, the cutting tool of which is hidden by 

 cylinder, B. 



Each half of the pattern is lifted from 

 its "bed" and the two hollowed parts 

 are placed carefully together with a 

 core, for shaping the interior, in the 

 centre. The molten iron is poured in 

 until it entirely fills the place from 

 which the wooden pattern was taken. 



The next step is to take this cylinder 

 to a boring mill where its inner sur- 

 face is made perfectly round and 

 smooth 



Fig. 6. — Engine assembled ready for installation in 

 boat. 



Fig. 7. — Ordinary gasoline is vaporized and mixed 

 with the proper proportion of air in a carburetor (not 

 shown here) and admitted to the explosion chamber 

 (A) while the piston (S) is at its lowest position. 

 When the piston returns the gas is compressed. When 

 the piston has reached its highest position and just as 

 it starts down, the gas is exploded in the chamber (A) 

 by an electric spark from spark plug (F). The 

 straight motion of the piston is converted into circu- 

 lar motion by the connection of the piston with the 

 balance wheel (EE), which is spun around in direc- 

 tion of dotted arrow. The propeller is connected with 

 the end of the shaft on which the balance wheel is 

 fastened. The piston rings are shown at G. As 

 the cylinder is made extremely hot by the exploding 

 gas, it must be cooled. This is done by pumping 

 cold water through the chamber (H) which surrounds 

 the explosion chamber. 



