Blisworth Limestone Formation today in the seas off the Bahamas (Kirkaldy p. 59). Much of it also contains marine shells, notably of oyster. Subsequently, the site was submerged less deeply so that the overlying Blisworth Clay was deposited in brackish conditions. (Gallois p. 20) The stratum is known as Blisworth Limestone because it was first studied at Blisworth in Northamptonshire when the Blisworth tunnel was being dug for what is now called the Grand Union Canal. The tunnel finally opened in 1805. Blisworth limestone is a generally thin but widely spread deposit in eastern England. It becomes thicker as one progresses southward from
Indigo Tunnel of the parallel Baltimore and Ohio railroad line on the opposite side of the Potomac River. The tunnel was acquired by the National Park Service in 1980 and became part of Chesapeake and Ohio Canal National Historical Park. The Park Service has identified bat colonies living in the tunnel and has closed the tunnel to the public in order to protect the colonies. Indigo Tunnel Indigo Tunnel is an abandoned railroad tunnel in Allegany County, Maryland, located about east of Little Orleans. Built by the Western Maryland Railway (WM) in 1904, Indigo was the company's longest tunnel. It was part