THE ENGINE PROPER, 67 



between the high- and low-pressure cylinders. In the side 

 view, the rings G and B are removed. The center-head is 

 represented by A. The iron-packing rings D and E are each 

 in three parts or segments and are held in their proper places 

 by the spring C. These segments of rings are so placed that 

 they "break joints," as can readily be seen from the side ele- 

 vation. They are held in position, relative to each other, by 

 the dowel pin, H. These packing rings are held in place by 

 the ring B, and also by the ring G, which is fastened to the 

 head with three cap-screws, F. The head is held in its posi- 

 tion between the cylinders by set-screws, as can readily be 

 seen from cut on page 64. 



To Test the Center-Head Packing, set the reverse lever 

 fcr, say, the threshing motion and turn the engine in the 

 direction in which it would run, just past the crank-end 

 dead-center. Block the cross-head so that the crank-shaft 

 cannot revolve, disconnect the cylinder-cock rod, and open 

 the throttle. This will admit steam on the crank-end of the 

 high pressure cylinder, and if the cylinder-cock on the head- 

 end of the low-pressure cylinder blows steam when opened, 

 it can come only from leakage of the metallic packing in the 

 center-head. 



