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
Cincinnati and Whitewater Canal Tunnel canal tunnel near the village of North Bend, which was finished six years before the canal opened for business. This tunnel was needed because of a steep ridgeline on the village's northern side, separating it from Cleves, on land owned by retired war hero William Henry Harrison, who as one of the canal's proponents was happy to sell land for its right-of-way and to supply wood and bricks for the tunnel. After his ascension to the presidency and sudden death, Harrison was buried atop the ridgeline near the tunnel's southern portal. Lined with brick, the tunnel includes ashlar stonework portals