[Sidenote: _Main Engines_]

The main engines are similar in type to those installed in the 74th
Street power house of the Manhattan Division of the Interborough Rapid
Transit Company, i. e., each consists of two component compound
engines, both connected to a common shaft, with the generator placed
between the two component engines. The type of engine is now well
known and will not be described in detail, but as a comparison of
various dimensions and features of the Manhattan and Rapid Transit
engines may be of interest, the accompanying tabulation is submitted:

Manhattan. Rapid Transit.

Diameter of high-pressure cylinders, inches, 44 42
Diameter of low-pressure cylinders, inches, 88 86
Stroke, inches, 60 60
Speed, revolutions per minute, 75 75
Steam pressure at throttle, pounds, 150 175
Indicated horse power at best efficiency, 7,500 7,500
Diameter of low-pressure piston rods, inches, 8 10
Diameter of high-pressure piston rods, inches, 8 10
Diameter of crank pin, inches, 18 20
Length of crank pin, inches, 18 18

Double Ported Single Ported
Type of Low-Pressure Valves. Corliss Corliss
Type of High-Pressure Valves. Corliss Poppet Type

Diameter of shaft in journals, inches, 34 34
Length of journals, inches, 60 60