load-bearing rails and a central gripper-traction rail, but it has habitually been referred to as a monorail in published sources despite not being one. There is a passing resemblance to the Lartigue Monorail, which in contrast had a central load-bearing rail and two lower guide rails. In 1876, the Cambridge Historical Commission began a campaign to attach Blue Oval Historical Markers to buildings on sites of historical importance. One was attached to the old Genoa Packing Company building, not at number 225 (which is the Alles Building) but at 221 next door. This was demolished in 2013, and replaced by the Fairfield Inn & Suites which is part of the Marriott chain. The plaque has not reappeared, and is listed by the commission as "marker not currently installed". The text read: "Meigs' Experimental Railway. Joseph V. Meigs, inventor and entrepreneur, successfully tested a steam-powered elevated monorail train intended for rapid transit use in Boston. 1886." Joe Meigs's extensive collection of papers and drawings relating to the system, as well as correspondence and genealogical material, is held at the Manuscripts and Archives Department of the Sterling Memorial Library at Yale University. An early notebook of his, 1854–66, includes early sketches of parts of the system and is part of the MIT Libraries collections. Layout of experimental line The following description is based on a plan, with annotations, published in The Meigs Railway System: The Reasons For Its Departures From The Ordinary Practice, page 177. The company's premises were on the north side of Bridge Street, number 225 (now Monsignor O'Brien Highway). This road runs roughly east to west. Just west of the company offices, adjacent to and parallel with the street, was a car shed with an adjacent workshop on its north side. Both ends of the shed had large doors through which the train could run. The experimental line ("trial road") began west of the shed and ran through it at just above ground level, but then rose on a continuous gradient of 2% round a 180 degree curve of 50 feet (15 metres) radius and 165 feet (50 metres) long. The line then ran west parallel to the north side of the car shed, before turning on a 45 degree curve before continuing south-west across the street to its terminus. This section to the second curve also had sections of grades, variable at 4.5%, 5.7% and finally 6.5% on