air. While buildings with deep subbasements could connect directly to the tunnel, connections to surface level and shallow basements were by elevator shafts. George W. Jackson, the contractor who built the tunnel system, received several patents related to building such shafts. Equipment Motive power The first test trains were run a few years after the start of construction. Most of the tunnel system was operated using overhead lines and trolley poles for power. Between 1903 and 1904, the Illinois Telephone Construction Company purchased 22 class L. M. locomotives from General Electric. These weighed and had two traction motors. Most of the engines used in the tunnels were standard mine haulage locomotives made by the Jeffrey Manufacturing Company. These weighed and had two traction motors each. Commonwealth Edison provided the electric power at 250 volts. On the grades leading up from the tunnel to the Grant Park disposal station, the Morgan system sold by the Goodman Equipment Mfg. Co. was used. Morgan locomotives used a central third rail for power and also as a rack for traction. This system was also widely sold to the mining industry and was particularly valuable where mines had steep grades. Temporary Morgan third-rail was installed in the tunnels during installation of the telephone cables on the tunnel ceiling, but after construction was completed, the Morgan system was only used in the context of the grade to the Grant Park disposal station and its use ceased with the closure of that disposal station. Between 1906 and 1908, the tunnel company purchased a number of Baldwin engines. One of these, number 508, was recovered from the tunnel leading to the Field Museum in 1996, when the rebuilding of the Outer Drive past the museum uncovered the old Grant Park Disposal Station elevator shaft. While not functional, this engine and cars is now on display in the collection of the Illinois Railway Museum. By 1914, the tunnel company was operating two gasoline powered locomotives built by Baldwin Locomotive Works on the surface trackage in Grant Park. These engines weighed and were long, wide and high. The 4-cylinder engines were coupled to the driving wheels through a jackshaft and side rods. These machines had a two-speed transmission with a top speed of . Freight cars The standard freight cars on the tunnel were long and wide, running on two 4-wheel trucks and designed to operate on curves with a