per square inch of section of the metal; the thickness of the metal of the trunnion bearings of oscillating engines should be 1/32d of the diameter of the cylinder, and the breadth of the bearing should be about half its diameter.

The trunnion bearings, instead of being liable to heat like other journals, are kept down to the temperature of the steam by the flow of steam passing through them; and the trunnion packings are not liable to leak when the packings, before being introduced, are squeezed in a cylindrical mould.

It is not expedient to cast the trunnion plummer blocks upon the lower frame, as is sometimes done; for the cylinders, being pressed from the steam trunnions by the steam, and drawn in the direction of the condenser by the vacuum, have a continual tendency to approach one another; and as they wear slightly toward midships, there would be no power of readjustment unless the plummer blocks were movable.

Q.How are the trunnion plummer blocks made?

The projection of the outer face of the trunnion flange from the side of the cylinder is 6-1/2 inches; the thickness of the flange round the mouth of the cylinder is 3/4 of an inch, and its projection 1-3/8 inch; the height of the cylinder stuffing box above the cylinder cover is 4-1/8 inches, and its external diameter 4-3/8 inchesthe diameter of the piston rod being 2-1/8 inches.

To ascertain whether the trunnions stand in a transverse plane, parallel to the cylinder flange, it is only necessary to measure down from the flange to each trunnion centre; and if both these conditions are satisfied, the position of the centres may be supposed to be right.

The flanges of the trunnions should always fit tight against the plummer block sides, but there should be a little play sideways at the necks of the trunnions, so that the cylinder may be enabled to expand when heated, without throwing an undue strain upon the trunnion supports.