Development of Locomotive 3 7 



tinct in action. They are pivoted in such 

 a way that the locomotive swings easily 

 round a curve. In the ' Mallet " com- 

 pounds the high-pressure steam will be 

 used in one set of cylinders, and then, by 

 means of flexible pipes, the steam will be 

 conveyed to the low-pressure cylinders on 

 the other set of machinery. A very econom- 

 ical locomotive results, especially suitable 

 for freight trains. 



The " Garratt " has also two sets of 

 machinery, and they may be compound or 

 simple. But here there is a great difference 

 found in the design of the engine generally. 

 The boiler is usually very big, and is carried 

 upon the two ends of the carriage which 

 contains the cylinders, etc. The space be- 

 tween the two carriages is left open so that 

 anyone could scramble underneath the 

 boiler. A very powerful engine is possible 

 on the Garratt plan because the boiler can 

 be made to almost any size; there are no 

 wheels to interfere with its dimensions, and 

 a very large fire-box is possible. These 

 engines have been used a good deal in 



