Invented in 1906 by an electrical engineer named T. B. Powers of the United States. The Eureka clock was the first electrically maintained balance-wheel clock. Convinced that he had devised a perfect timekeeper, Powers called his clock 'Eureka' that in Greek meant I found it. Manufacture did not start until 1909. The earliest models were enclosed under a glass dome where the large compensated balance could be seen swinging. Later models were fitted in a variety of cases. Many of the Eureka clocks have only 'Eureka Electric Clock - 1000 days' on the dial to indicate that the clock is electric. Timekeeping did not prove as good as Powers had hoped, though the clock made with the balance and mechanism visible had a powerful novelty appeal. The arm of the balance is a soft iron core with two soft iron arms which form a U-shaped magnet when current passes through its solenoid winding. A silver pin on the balance arm touches a fixed silver contact at the correct point for impulsing the balance, the balance arm being attracted to a fixed soft iron armature; the resulting swing operates a cam on the balance arbor to move the clock train through a pawl and ratchet wheel. About 10,000 of these clocks were made before manufacture ceased in 1914.