CHAPTER XL.

=THE INDICATOR.=

=Computations from Indicator Diagrams= 413 =Indicators= 413 Description of 413 Thompson indicator 413 Tabor indicator 413 Diagrams 414 Admission of steam to indicator 414 Expansion line or curve 414 Exhaust line 414 Back pressure line 414 Atmospheric line 414 Theoretical diagram 414 Compression line or curve 415 Condensing engine diagram 415 Vacuum line of indicator diagram 415 (Barometer, construction of) 415 (Barometer, graduation of) 416 Indicator springs 416 Tables of springs for indicators 416 Attachment of indicators to an engine 416, 417 Pantagraph motions 417 Expansion curve, testing of 417, 418 Theoretical expansion curve 417, 418 Calculations from diagrams 418 to 421 Horse power 418, 419 Area 419 Rule for calculating horse power 419 Mean effective pressure 420 Steam used in engines 420 Water consumption 420, 421 Defective diagrams of engines 421 Excessive lead of engines 421 Theoretical compression curve of engines 422