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
Sapperton Canal Tunnel short section to create a passing basin. Sapperton Tunnel was passable until at least 1966 but is now blocked by roof collapses over several hundred yards, mainly in sections where the ground is fuller's earth. Restoration is proposed by the Cotswold Canals Trust as part of their project to re-open the canal route from Thames to Severn. The trust operates tourist boat trips into the tunnel in winter months. The Sapperton railway tunnel, on the Golden Valley Line, follows a broadly similar route under the 'Cotswold Edge'. There have been proposals for a national network of canals and aqueducts to