MARINE ENGINES. . 365

be left in the pattern, placed at the angle the valve is designed for,and the valve can thus be turned to fit the seating exactly.

The lubricating citps should be plain, having pipes passing downto the bearings, fitted with siphon wicks; and they should havecovers to prevent dirt lodging in them. Some engineers cast thecups on the various parts, while others prefer light cups cast inbrass. Fig. 248 shows the lubricator cup with hollow plug fitted tothe cylinder cover for lubricating the piston.

SLIDE-VALVE GEAR.

The slide-valve gear for the oscillating engine differs so muchfrom other arrangements that it requires to be treated somewhat indetail. The mode of setting out this valve motion has been already

1 1

Fig. 249.—-Slide Valve. 1

a, Slide valve. b, Ring for taking off the back pressure, c, Valve spindle. d, Valve casing.e, Valve-casing cover. f, Cylinder.

described, and although the various plans adopted may differ indetail, the motion produced is the same in all. Take, for example,

1 In this section the various figures are diminished as in working drawings for theWorkshop.