Date: 1894
201. communicate crosswise with the ends of the valve-chest; that is to say, D is connected with the end R', and D' with the end R. Bearing these details of construction in mind, the action of the drill can be followed.  The drawing shows the machine ready to begin its forward stroke.  The rear end of the valve-chest is con nected with D, which is closed by the piston, whdst the front R is open through D' and the annular recess S to the port F and the atmosphere.