In the late 1970s the Cape Breton Development Corporation delineated a submarine coal resource off Cape Pierce on Cape Breton Island, Nova Scotia, Canada. Following a project definition study, site work commenced at the Donkin-Morien Development Project in 1980. In 1981/82 a demonstration of an experimental tunnel boring machine took place in the second tunnel. The experimental unit was a 4 m diameter earth tunnelling machine modified by Lovat Tunnel Equipment Inc, Beaver Underground Structures and Hughes Tool Ltd to carry a rock-cutting head. Success led to a decision to construct a prototype 7. 6 m diameter machine which is described.