The remains of a small 'horizontal' mill (probably about 3 metres square in its original form), situated at the foot of Ballaglass Glen, Cornaa was inspected by W. Gill, B.R.S. Megaw and Mr Gelling (son of the former Cornaa miller) in 1940. The north wall still survived from 1.2 to 1.8 metres high at that time. The pivot or socket stone on which the vertical axle revolved, was found previously by Mr Gelling, but was washed away in the flood of 1929. A plan of the Ballaglass estate made in 1779 marks the mill.  The origin of the name may be Norse i.e. Cornaa = Kvern-a (mill river). Horizontal mills were well-established in the island at least by the 13th century.