Report on the Trials of Implements at Wolverhampton. 509 
■s''lf-acting brake into play. Avoiding the rattle and wear of sliding clutches 
or pinions, Messrs. Howard key two inallcablo-iron pinions upon the driving- 
shaft, wliioli receives motion from the engine crauk-shaft by a coupling with 
;imiversal joints ; and the rope-drums are hung Tipon hollow axes or bosses set 
•eccentrically upon a fi.xcd axle, so that by partially turning these centres by 
Jcver-handles for the purpose, the drums are raised or depressed, setting the 
cog-teeth of the flanges in or out of gear with the pinions. And the same 
movement which diops a drum out of gear leaves it resting, by the inner side 
of its ilange or rim, upon a fixed block, which thus serves as a brake. 
The compensating double snatch-block is a contrivance for recovering upon 
the puUing-rope a portion of the motive power which is lost in retarding, or 
rather maintaining a degree of tension in the outgoing rope. It is owing to a 
icommon misunderstanding as to the action of this apparatus that it is often set 
•down in an improper position and its whole value sacrificed and Fig. 20, 
Fig. 20. — Diagram-plan of Messrs. J. and F. HoicarcVs Compensating 
Double Snatch-block. 
which is a plan not drawn to scale, may assist in an explanation. A and B 
Are the two pulleys, mounted upon a rectangular frame held fast to the ground 
iby stakes, C C C C, driven deeply in, the iron cheeks also being made to pene- 
trate the soil and thus tend to secure the frame against shifting its position. 
A third and smaller pulley, D, is mounted upon a loose bar, E, which is centred 
-at F upon the frame, so that the pulley D is at liberty to approach one or other 
•of the two fixed pulleys A and B. Thus, when L is the pulling rope, as in the 
figure, passing in the direction of the arrow towards the windlass, it forces the 
movable pulley D towards the fixed pulley A, and, in fact, i:)resses a ring or 
tiange, J, against the rim of the pulley A. On the contrary, when K is the 
tight or pulling rope, it presses the ring J of the pulley D in contact with the 
uim of the pulley B. The ring J, being of smaller diameter than the pitch-line 
