THE INDICATOR DIAGRAM.

137

cylinder, or down stroke of the low-pressure piston. For largepower this is an advantage, as the descent of the large piston is

High and Low Pressure Cylinders combincd.

Top*

Total indicated power, 1551.

Steam, 40 lbs. Vacuum, 28 inches. Revolutions, 33.

Figs. 82, 83.— Compound Engine Eiagrams.

better balanced than if great steam pressure was admitted into thecylinder. Again, when the steam is raising the small piston, it willbe seen that more steam is admitted, the cut-off taking place at alater period. The diagram for the large cylinder shows steam pres-sure above the atmospheric line for a very short period, which ofcourse is beneficially utilized in raising the large piston. Thesetwo diagrams admirably show the action of the slide-valve, theopening of the valve being greater for the IN stroke than for theOUT stroke. This takes place with valves having the same amountof cover on each steam end, actuated by an eccentric motion.

For reading off the steam and vacuum measures the diagram is