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 LXVII. 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.