136 



THAT'S IT ; 



THE STEAM LOCOMOTIVE. 



442. 



A, the steam receiver; B, handles for turning steam off or on; above and behind wh'ch is a steam gauge r to 

 indicate the pmssur** of steam in t>e receiver; C, a safety valve, closed by a spiral spring, wh'ch yields under 

 excessive pressure; D, the boiler, to which there is a circular mooeable top, which is taken off when the boiler 

 requires cleaning; E, opening of the furnace; F, the fire-box ; G, the driving wheel, the axle of which is con- 

 nected by cranks with the piston rods of two cylinders that lie horizontally between the front wheels; H t the 

 fender which throws obstacles off the rails I, the buffers, which modify concussion. 



The locomotive is the result of 

 the application of the steam-en- 

 gine to produce progressive motion, 

 instead of simply exerting station- 

 ary force from a given position. 

 The piston rod, or rods, which in 

 the stationary engine are fixed to 

 a beam, imparting thereto an up- 

 ward and a downward movement, 

 are, in the locomotive, attached 

 either to cranks (bends, or turns) 

 iu the axle, or to pivots upon the 

 spokes of the wheels, so that as 

 the pistons work, they communi- 

 cate a rotary motion to the wheels, 

 and the body resting upon the 



wheels, or attached to them, is 

 impelled in the direction of the 

 rotation. 



The explanation of the struc- 

 ture of the first steam locomotive 

 will greatly simplify the descrip- 

 tion of the more perfect engines 

 now in use, since the principle of 

 their construction is the same. 



The fire-box, 1, imparts heat to 

 the boiler, 2 ; the steam from which 

 enters the cylinder, 5 ; the motion 

 of the pistons being communicated 

 to the driving wheels, 9, by con- 

 necting rods, attached to pivots 

 placed upon the spokes. 



