Glace Bay (glās) [key], town (1991 pop. 19,501), E Cape Breton Island, N.S., Canada. Exploitation of its coal mines began toward the end of the 19th cent., but declined in the 1960s; the last mine in the region closed in 2001. Its mines extended for several miles under the sea and were among the best equipped in the world. Glace Bay has a good harbor and relies heavily on its large deep-sea fishing fleet. The Marconi wireless tower at Table Head nearby was the transmitter in 1902 of the first transatlantic wireless message.