C is a hollow cylinder or shell, with a part of one end formed into a cam proper.  Throughout the whole length of this piece, upon the inside, there is a spiral groove cut to receive one end of a feather, by which its pitch or eccentricity is regulated. C’ is also a hollow cylinder or shell, of the same length and diameter as C, with a similar spiral groove cut on the inside, the outside being perfectly smooth and plain, upon which the toe (t) for closing the valves is fastened.  The inside piece consists of two hubs D, D’, eccentric with each other, and made in one piece, D being turned to exactly fit the inside of the shell C, and D’ to fit the shell C’, the hub D’ having a socket (c) into which the spindle (s) of the governor is screwed; the end (d) of the hub D forming a journal or bearing, with a bevel wheel on its extremity to convey motion from the crank-shaft gearing to the governor and cut-off.  There is a hole throughout the length of the inside hubs D and D’, which is continued through the spindle of the governor, and contains the rod (r) that connects the cam with the governor.  This hole is eccentric to the outside surface of the hub D, as well as to the shell C, and concentric with the hub D’ and shell C’, and with the governor rod (r).

The shell C and hub D, and shell C’ and hub D’, are connected together by feathers; one piece of each feather is of a spiral form, and the other a straight or rectangular piece, the two being connected together by a stub on the rectangular piece, which fits into a hole or bearing in the other or spiral piece, so that the latter can turn on the stub and accommodate itself to the groove in which it has to work.  The spiral part of each feather works in the spiral groove on the inside of its corresponding shell C and C’ respectively, and the rectangular pieces work in a straight groove cut in the hubs D and D’, the inner parts of the rectangular pieces being fastened to the governor rod (r), so that the feathers are permanently connected with the governor.

The shell C’ revolves inside of two yokes (y) and (y’), one attached to each steam-valve toe, (a) and (a’) respectively.

On the inside of each yoke, and opposite to its valve-toe, is a raised piece, against which the closing piece (t) on the shell (C’) acts to close the valves.

This shell (C’), as before noticed, has a spiral groove on its inside, similar in all respects to that in the cam-shell (C); and being acted upon in the same manner and through the same rod by the governor, it is evident that the closing piece (t) on its outside will always hold the same relation to the opening toe on the lower or cam-shell (C); and whatever alteration is made in the one, a corresponding alteration takes place in the other, thereby insuring the closing of the valves at the proper time at every point of the variation of the cut-off.