SARNIA, a town and port of entry, Ontario, Canada, capital of Lambton county, 55 m. N.E. of Detroit, on the left bank of the river St Clair. Pop. (1901) 8176. It is on the Grand Trunk and Lake Erie & Detroit River railways, and is a port of call for steamers plying on the Great Lakes. It contains a large oil-refinery which handles the greater part of the product of the Ontario oil region. The Grand Trunk railway crosses the river at this point by the St Clair tunnel, 6025 ft. long or, including the approaches, 2¼ m., which connects the town with the American city of Port Huron (Michigan).