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friction wheels, which, while preserving with the utmost 
exactness the direction of the axis of the guide tube and 
rocket, permits the guide tube and rocket to revolve on its 
axis with all due facility. 
The requisite amount of axial rotation is conveyed to the 
guide tube and thence to the rocket resting within it, by 
means of a powerful clock spring S, transmitting its rotation 
to the rocket through the train of wheels C', C", C'". 
Previous to firing the rocket the wheel C" is locked by 
the catch or trigger D ; the spring S is then wound up and 
the aim and elevation of the rocket adjusted. The match 
