EXPLANATION OF THE PLATES. 397 



the line A, fig. 1. The balance terminates with a bent rod, B, somewhat of the 

 curvature of part of the boiler to which it is attached by the screw C. The semi- 

 cylindrical cylinder D contains a strong helical spring, which, by its extension or 

 contraction, (occasioned by the rising or falling of the lever E, fig. 1,) moves a 

 vernier upon the face F of the balance, indicating the power employed in raising 

 or extending the spring. The face upon which the vernier moves is graduated ac- 

 cording to the elasticity of the spring. The metallic circular and mitred valve G, 

 fig. 1, is operated upon its under side by the steam, which rises from the interior of 

 the boiler, passing through the chamber H, fig. 1, and again through a series of 

 holes drilled in the seat of the valve I, fig. 1 ; the valve preserves its parallelism 

 by the spindle K being guided in the tube L. Fig. 3 is a top view or plan of the 

 whole apparatus. 



Fig. 4 represents the construction of the spring safety valve, differing only from 

 that represented above by the pressure of the steam being directly applied to 

 the congeries of springs C C C without the intervention of the lever before described. 

 This valve is usually covered and protected by a trumpet-shaped pipe, so that it 

 may not be improperly loaded or tampered with by any one employed about the 

 engine ; neither are the springs so stiff as those employed in the lever valve, conse- 

 quently any escape of steam from the boiler is first blown off through this valve 

 and gives the requisite notice for checking the intensity of the fire. 



Fig. 5 is a plan of the cap at A, fig. 4. Fig. 6 is a plan of the valve at B, fig. 4. 



PLATE LXVIL A. 



CYLINDER COVER AND CONNECTING RODS, STANHOPE AND TYNE 



LOCOMOTIVE ENGINE. 



Plate V., fig. 1. The cylinder cover of the Stanhope and Tyne engine. A, the 

 brass stuffing through which the piston-rod alternates. B B, brass stuffing piece. 



Fig. 2. Side view of one end of the outside connecting-rods. A, wrought iron 

 strap, secured to the connecting-rod by the gib and key ; the brasses B B are 

 brought to their bearings by tightening the key C. A set screw at A, fig 3, 

 secures it in its position ; the brasses of these connecting rods work on a ball end 

 crank pin, as shewn at B, fig. 3, which is a section of the end of the connecting- 

 rod. 



