Many men claim for this engine that the closing occurs when the cut off eccentric is moving its fastest.  This is a fact, and if we consider the point of cut off only to be the point of absolute cut off, the cut off must be instantaneous, for there is an instantaneous point where the cut off is final only to be considered.  The reasoning applied here would hold good also to a less extent on the slide valve, but is not the point of absolute cut off.  We want to note how long it is from the time the valve commences to close at all until finally closed, and, as I have shown you, this is considerable in this engine.

Referring to the point of cut off finally, it is determined upon by a governor of the fly wheel type.  The eccentric is loose about the shaft, and arms projecting therefrom are connected by other arms to the extremity of an arm upon which is mounted a weight, and which is attached to the spokes of the fly wheel, or special governor wheel in this case, and which is fastened to the crank shaft.  As the speed increases through throwing off a portion of the load the governor weights fly out, and this movement is transferred through the lever connections to the eccentric, causing it to be turned ahead, and the manner hastening the movement of the cut off valve on its seat and causing it to reach and cover the edge of the steam port earlier in the stroke.  This engine was the pioneer in governors of this character, the advantage being, in addition to its necessity for the work of turning the eccentric ahead or back, that the liability of the engine to run away, as very often happens from the breaking of the governor belt or a similar cause, was not possible.

The cut off valve has a travel considerably beyond the edge of the steam passage after the valve is closed, and this has one advantage, that the valve is less liable to leak, and to this must be added the loss from the friction of this moving valve, and moving too in opposition to the main valve.  In our perfect valve, as we outlined it, the valve does not move after the port is closed.  The exhausting functions of the valve are very good, giving a quick opening and a full opening, because this opening occurs when the eccentric is moving its fastest.  The engine also possesses a distinct advantage in having remarkably small clearance spaces.  The length of the steam passage is very small in comparison with any form of engine, and having but two ports instead of four, as in the Corliss and four valve type.

In these there must be included in the clearance, that to the exhaust port as well as the steam port, adding a considerable amount where the piston comes close to the head.  As the engines leave the maker’s hand the engines are provided with a considerable amount of lap to give plenty of compression, but are, of course, capable of having more added to increase compression, or some planed off to decrease it.