The Englishman's arms shot into the slime with the regularity of pistons.
The horse's shoulders felt like pistons working under a cloth.
It was on the lever principle, the cylinders, instead of the pistons, being movable.
This end thrust is counterbalanced by means of the "dummy" pistons, P1, P2, P3.
From the beginning Hobart has had a mania for screws, bolts, nuts, and pistons.