Michigan Supreme Court February 18, 1897 (Turner v. St. Clair Tunnel Co.)

Hooker, J.

The defendant is a corporation, and was engaged in constructing a tunnel under the St. Clair river between Ft. Gratiot, Mich.; and Port Sarnia, Ontario. Compressed air was used to prevent caving, access to the tunnel being had through an air lock, in which the air was made to correspond in density with that in the tunnel, or with that of the atmosphere outside, by the use of valves.