The “lap” and “lead” are opened by the action of the valve lever acting as a lever, and the port opening is given by the incline of the curved slide in which the center of that lever slides, and the amount of this opening depends upon the angle given to that incline.  When these two actions are in unison, the motion of the valve is very rapid, and this occurs when the steam is being admitted.  Then follows a period of opposition of these motions, during which time the valve pauses momentarily, this corresponding to the time when the port is fully open.  Further periods of unison follow, at which time the sharp “cut-off” is obtained.

The “compression” resulting with this gear is also reduced to a minimum, owing to the peculiar movement given to the valves (i. e., the series of accelerations and retardations referred to), as, while the “lead” is obtained later and quicker, the port is also shut for “compression” later and quicker, doing away with the necessity for a special expansion valve, with its complicated and expensive machinery, and allowing the main valve to be used for expansion, as the “compression” is not of an injurious amount, even with a “cut-off” reduced to 15 per cent., or about 1/6 of the stroke.

Thus, so far as the distribution of the steam and its treatment in the cylinder is concerned, a marked advantage is shown in favor of this valve gear.  But next in its favor, as before said, is that the above advantages are not gained at the cost of added complication of parts or increased cost of machinery, but the reverse, as this gear can be built at a less cost than link gear, varying according to the circumstances, but reaching as high as a saving of 25 per cent., or, if it be compared with a link gear supplemented by the usual special expansion valve and gear as employed on marine engines, then the total saving is fully 50 per cent., and an equally good result is obtained as to the distribution and subsequent treatment of the steam.

After accuracy of result and reduction in cost may rank saving room and the advantages arising therefrom (though for steamships perhaps this should have come first).  Taking locomotives of the inside cylinder type, which is the general form in use in England and the continent of Europe, by clearing away the eccentrics and valves from the middle of the engine, much larger cylinders may be introduced and a higher rate of expansion employed, and this is being done.  Also room is left for increasing the length and wearing surfaces of all the main bearings with even less crowding than is now the case with engines with the smaller cylinders.